1 \chapter{Data Representation}
2 \label{datarep:datarepresentation}
4 This section describes the binary representation of the
5 debugging information entry itself, of the attribute types
6 and of other fundamental elements described above.
9 \section{Vendor Extensibility}
10 \label{datarep:vendorextensibility}
11 \addtoindexx{vendor extensibility}
12 \addtoindexx{vendor specific extensions|see{vendor extensibility}}
15 \addtoindexx{extensibility|see{vendor extensibility}}
16 reserve a portion of the DWARF name space and ranges of
17 enumeration values for use for vendor specific extensions,
18 special labels are reserved for tag names, attribute names,
19 base type encodings, location operations, language names,
20 calling conventions and call frame instructions.
22 The labels denoting the beginning and end of the reserved
23 value range for vendor specific extensions consist of the
24 appropriate prefix (DW\_TAG, DW\_AT, DW\_END, DW\_ATE, DW\_OP,
25 DW\_LANG, DW\_LNE, DW\_CC or DW\_CFA respectively) followed by
26 \hypertarget{chap:DWXXXlohiuser}{}
27 \_lo\_user or \_hi\_user.
28 \textit{For example, for entry tags, the special
29 labels are DW\_TAG\_lo\_user and DW\_TAG\_hi\_user.}
30 Values in the range between \textit{prefix}\_lo\_user
31 and \textit{prefix}\_hi\_user inclusive,
32 are reserved for vendor specific extensions. Vendors may
33 use values in this range without conflicting with current or
34 future system\dash defined values. All other values are reserved
35 for use by the system.
37 \textit{There may also be codes for vendor specific extensions
38 between the number of standard line number opcodes and
39 the first special line number opcode. However, since the
40 number of standard opcodes varies with the DWARF version,
41 the range for extensions is also version dependent. Thus,
42 \livetarg{chap:DWLNSlouser}{DW\_LNS\_lo\_user} and
43 \livetarg{chap:DWLNShiuser}{DW\_LNS\_hi\_user} symbols are not defined.
46 Vendor defined tags, attributes, base type encodings, location
47 atoms, language names, line number actions, calling conventions
48 and call frame instructions, conventionally use the form
49 \text{prefix\_vendor\_id\_name}, where
50 \textit{vendor\_id}\addtoindexx{vendor id} is some identifying
51 character sequence chosen so as to avoid conflicts with
54 To ensure that extensions added by one vendor may be safely
55 ignored by consumers that do not understand those extensions,
56 the following rules should be followed:
57 \begin{enumerate}[1. ]
59 \item New attributes should be added in such a way that a
60 debugger may recognize the format of a new attribute value
61 without knowing the content of that attribute value.
63 \item The semantics of any new attributes should not alter
64 the semantics of previously existing attributes.
66 \item The semantics of any new tags should not conflict with
67 the semantics of previously existing tags.
69 \item Do not add any new forms of attribute value.
74 \section{Reserved Values}
75 \label{datarep:reservedvalues}
76 \subsection{Error Values}
77 \label{datarep:errorvalues}
78 \addtoindexx{reserved values!error}
81 \addtoindexx{error value}
82 a convenience for consumers of DWARF information, the value
83 0 is reserved in the encodings for attribute names, attribute
84 forms, base type encodings, location operations, languages,
85 line number program opcodes, macro information entries and tag
86 names to represent an error condition or unknown value. DWARF
87 does not specify names for these reserved values, since they
88 do not represent valid encodings for the given type and should
89 not appear in DWARF debugging information.
92 \subsection{Initial Length Values}
93 \label{datarep:initiallengthvalues}
94 \addtoindexx{reserved values!initial length}
96 An \livetarg{datarep:initiallengthvalues}{initial length field} is one of the length fields that occur
98 of those DWARF sections that
104 \dotdebugpubnames{}, and
105 \dotdebugpubtypes{}) or the length field
106 that occurs at the beginning of the CIE and FDE structures
107 in the \dotdebugframe{} section.
109 In an \addtoindex{initial length field}, the values \wfffffffzero through
110 \wffffffff are reserved by DWARF to indicate some form of
111 extension relative to \addtoindex{DWARF Version 2}; such values must not
112 be interpreted as a length field. The use of one such value,
113 \xffffffff, is defined below
114 (see Section \refersec{datarep:32bitand64bitdwarfformats});
116 the other values is reserved for possible future extensions.
120 \section{Executable Objects and Shared Objects}
121 \label{datarep:executableobjectsandsharedobjects}
123 The relocated addresses in the debugging information for an
124 executable object are virtual addresses and the relocated
125 addresses in the debugging information for a shared object
126 are offsets relative to the start of the lowest region of
127 memory loaded from that shared object.
129 \textit{This requirement makes the debugging information for
130 shared objects position independent. Virtual addresses in a
131 shared object may be calculated by adding the offset to the
132 base address at which the object was attached. This offset
133 is available in the run\dash time linker\textquoteright s data structures.}
137 \section{32-Bit and 64-Bit DWARF Formats}
138 \label{datarep:32bitand64bitdwarfformats}
139 \hypertarget{datarep:xxbitdwffmt}{}
140 \addtoindexx{32-bit DWARF format}
141 \addtoindexx{64-bit DWARF format}
142 There are two closely related file formats. In the 32\dash bit DWARF
143 format, all values that represent lengths of DWARF sections
144 and offsets relative to the beginning of DWARF sections are
145 represented using 32\dash bits. In the 64\dash bit DWARF format, all
146 values that represent lengths of DWARF sections and offsets
147 relative to the beginning of DWARF sections are represented
148 using 64\dash bits. A special convention applies to the initial
149 length field of certain DWARF sections, as well as the CIE and
150 FDE structures, so that the 32\dash bit and 64\dash bit DWARF formats
151 can coexist and be distinguished within a single linked object.
153 The differences between the 32\dash\ and 64\dash bit
155 detailed in the following:
156 \begin{enumerate}[1. ]
158 \item In the 32\dash bit DWARF format, an
159 \addtoindex{initial length field}
161 \addtoindexx{initial length field!encoding}
162 Section \refersec{datarep:initiallengthvalues})
163 is an unsigned 32\dash bit integer (which
164 must be less than \xfffffffzero); in the 64\dash bit DWARF format,
165 an \addtoindex{initial length field} is 96 bits in size,
168 \item The first 32\dash bits have the value \xffffffff.
170 \item The following 64\dash bits contain the actual length
171 represented as an unsigned 64\dash bit integer.
174 \textit{This representation allows a DWARF consumer to dynamically
175 detect that a DWARF section contribution is using the 64\dash bit
176 format and to adapt its processing accordingly.}
178 \item Section offset and section length
179 \hypertarget{datarep:sectionoffsetlength}{}
180 \addtoindexx{section length!use in headers}
182 \addtoindexx{section offset!use in headers}
183 in the headers of DWARF sections (other
184 \addtoindexx{initial length field}
186 \addtoindex{initial length}
187 fields) are listed following. In the 32\dash bit DWARF format these
188 are 32\dash bit unsigned integer values; in the 64\dash bit DWARF format,
190 \addtoindexx{section length!in .debug\_aranges header}
192 \addtoindexx{section length!in .debug\_pubnames header}
194 \addtoindexx{section length!in .debug\_pubtypes header}
195 unsigned integer values.
199 Section &Name & Role \\ \hline
200 \dotdebugaranges{} & \addtoindex{debug\_info\_offset} & offset in \dotdebuginfo{} \\
201 \dotdebugframe{}/CIE & \addtoindex{CIE\_id} & CIE distinguished value \\
202 \dotdebugframe{}/FDE & \addtoindex{CIE\_pointer} & offset in \dotdebugframe{} \\
203 \dotdebuginfo{} & \addtoindex{debug\_abbrev\_offset} & offset in \dotdebugabbrev{} \\
204 \dotdebugline{} & \addtoindex{header\_length} & length of header itself \\
205 \dotdebugpubnames{} & \addtoindex{debug\_info\_offset} & offset in \dotdebuginfo{} \\
206 & \addtoindex{debug\_info\_length} & length of \dotdebuginfo{} \\
208 \dotdebugpubtypes{} & \addtoindex{debug\_info\_offset} & offset in \dotdebuginfo{} \\
209 & \addtoindex{debug\_info\_length} & length of \dotdebuginfo{} \\
211 \dotdebugtypes{} & \addtoindex{debug\_abbrev\_offset} & offset in \dotdebugabbrev{} \\
212 & \addtoindex{type\_offset} & offset in \dotdebugtypes{} \\
217 The \texttt{CIE\_id} field in a CIE structure must be 64 bits because
218 it overlays the \texttt{CIE\_pointer} in a FDE structure; this implicit
219 union must be accessed to distinguish whether a CIE or FDE is
220 present, consequently, these two fields must exactly overlay
221 each other (both offset and size).
223 \item Within the body of the \dotdebuginfo{} or \dotdebugtypes{}
224 section, certain forms of attribute value depend on the choice
225 of DWARF format as follows. For the 32\dash bit DWARF format,
226 the value is a 32\dash bit unsigned integer; for the 64\dash bit DWARF
227 format, the value is a 64\dash bit unsigned integer.
230 Form & Role \\ \hline
231 \livelink{chap:DWFORMrefaddr}{DW\_FORM\_ref\_addr}& offset in \dotdebuginfo{} \\
232 \livelink{chap:DWFORMsecoffset}{DW\_FORM\_sec\_offset}& offset in a section other than \\
233 &\dotdebuginfo{} or \dotdebugstr{} \\
234 \livelink{chap:DWFORMstrp}{DW\_FORM\_strp}&offset in \dotdebugstr{} \\
235 \livelink{chap:DWOPcallref}{DW\_OP\_call\_ref}&offset in \dotdebuginfo{} \\
239 \item Within the body of the \dotdebugpubnames{} and
241 sections, the representation of the first field
242 of each tuple (which represents an offset in the
244 section) depends on the DWARF format as follows: in the
245 32\dash bit DWARF format, this field is a 32\dash bit unsigned integer;
246 in the 64\dash bit DWARF format, it is a 64\dash bit unsigned integer.
251 The 32\dash bit and 64\dash bit DWARF format conventions must \emph{not} be
252 intermixed within a single compilation unit.
254 \textit{Attribute values and section header fields that represent
255 addresses in the target program are not affected by these
258 A DWARF consumer that supports the 64\dash bit DWARF format must
259 support executables in which some compilation units use the
260 32\dash bit format and others use the 64\dash bit format provided that
261 the combination links correctly (that is, provided that there
262 are no link\dash time errors due to truncation or overflow). (An
263 implementation is not required to guarantee detection and
264 reporting of all such errors.)
266 \textit{It is expected that DWARF producing compilers will \emph{not} use
267 the 64\dash bit format \emph{by default}. In most cases, the division of
268 even very large applications into a number of executable and
269 shared objects will suffice to assure that the DWARF sections
270 within each individual linked object are less than 4 GBytes
271 in size. However, for those cases where needed, the 64\dash bit
272 format allows the unusual case to be handled as well. Even
273 in this case, it is expected that only application supplied
274 objects will need to be compiled using the 64\dash bit format;
275 separate 32\dash bit format versions of system supplied shared
276 executable libraries can still be used.}
280 \section{Format of Debugging Information}
281 \label{datarep:formatofdebugginginformation}
283 For each compilation unit compiled with a DWARF producer,
284 a contribution is made to the \dotdebuginfo{} section of
285 the object file. Each such contribution consists of a
286 compilation unit header
287 (see Section \refersec{datarep:compilationunitheader})
289 single \livelink{chap:DWTAGcompileunit}{DW\_TAG\_compile\_unit} or
290 \livelink{chap:DWTAGpartialunit}{DW\_TAG\_partial\_unit} debugging
291 information entry, together with its children.
293 For each type defined in a compilation unit, a contribution may
294 be made to the \dotdebugtypes{}
295 section of the object file. Each
296 such contribution consists of a
297 \addtoindex{type unit} header
298 (see Section \refersec{datarep:typeunitheader})
299 followed by a \livelink{chap:DWTAGtypeunit}{DW\_TAG\_type\_unit} entry, together with
302 Each debugging information entry begins with a code that
303 represents an entry in a separate
304 \addtoindex{abbreviations table}. This
305 code is followed directly by a series of attribute values.
307 The appropriate entry in the
308 \addtoindex{abbreviations table} guides the
309 interpretation of the information contained directly in the
311 \dotdebugtypes{} section.
314 Multiple debugging information entries may share the same
315 abbreviation table entry. Each compilation unit is associated
316 with a particular abbreviation table, but multiple compilation
317 units may share the same table.
318 \subsection{Unit Headers}
319 \label{datarep:unitheaders}
321 \subsubsection{Compilation Unit Header}
322 \label{datarep:compilationunitheader}
323 \begin{enumerate}[1. ]
325 \item \texttt{unit\_length} (\livelink{datarep:initiallengthvalues}{initial length}) \\
326 \addttindexx{unit\_length}
327 A 4\dash byte or 12\dash byte
328 \addtoindexx{initial length}
329 unsigned integer representing the length
330 of the \dotdebuginfo{}
331 contribution for that compilation unit,
332 not including the length field itself. In the \thirtytwobitdwarfformat,
333 this is a 4\dash byte unsigned integer (which must be less
334 than \xfffffffzero); in the \sixtyfourbitdwarfformat, this consists
335 of the 4\dash byte value \wffffffff followed by an 8\dash byte unsigned
336 integer that gives the actual length
337 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
340 \item \texttt{version} (\addtoindex{uhalf}) \\
341 A 2\dash byte unsigned integer representing the version of the
342 DWARF information for the compilation unit \addtoindexx{version number!compilation unit}
343 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
344 The value in this field is 4.
346 \item \addttindex{debug\_abbrev\_offset} (\livelink{datarep:sectionoffsetlength}{section offset}) \\
348 \addtoindexx{section offset!in .debug\_info header}
349 4\dash byte or 8\dash byte unsigned offset into the
351 section. This offset associates the compilation unit with a
352 particular set of debugging information entry abbreviations. In
353 the \thirtytwobitdwarfformat, this is a 4\dash byte unsigned length;
354 in the \sixtyfourbitdwarfformat, this is an 8\dash byte unsigned length
355 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
357 \item \texttt{address\_size} (\addtoindex{ubyte}) \\
358 A 1\dash byte unsigned integer representing the size in bytes of
359 \addttindexx{address\_size}
360 an address on the target architecture. If the system uses
361 \addtoindexx{address space!segmented}
362 segmented addressing, this value represents the size of the
363 offset portion of an address.
368 \subsubsection{Type Unit Header}
369 \label{datarep:typeunitheader}
371 The header for the series of debugging information entries
372 contributing to the description of a type that has been
373 placed in its own \addtoindex{type unit}, within the
374 \dotdebugtypes{} section,
375 consists of the following information:
376 \begin{enumerate}[1. ]
378 \item \texttt{unit\_length} (\livelink{datarep:initiallengthvalues}{initial length}) \\
379 \addttindexx{unit\_length}
380 A 4\dash byte or 12\dash byte unsigned integer
381 \addtoindexx{initial length}
382 representing the length
383 of the \dotdebugtypes{} contribution for that type unit,
384 not including the length field itself. In the \thirtytwobitdwarfformat,
385 this is a 4\dash byte unsigned integer (which must be
386 less than \xfffffffzero); in the \sixtyfourbitdwarfformat, this
387 consists of the 4\dash byte value \wffffffff followed by an
388 8\dash byte unsigned integer that gives the actual length
389 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
392 \item \texttt{version} (\addtoindex{uhalf}) \\
393 A 2\dash byte unsigned integer representing the version of the
394 DWARF information for the
395 type unit\addtoindexx{version number!type unit}
396 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
397 The value in this field is 4.
399 \item \addttindex{debug\_abbrev\_offset} (\livelink{datarep:sectionoffsetlength}{section offset}) \\
401 \addtoindexx{section offset!in .debug\_types header}
402 4\dash byte or 8\dash byte unsigned offset into the
404 section. This offset associates the type unit with a
405 particular set of debugging information entry abbreviations. In
406 the \thirtytwobitdwarfformat, this is a 4\dash byte unsigned length;
407 in the \sixtyfourbitdwarfformat, this is an 8\dash byte unsigned length
408 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
410 \item \texttt{address\_size} (ubyte) \\
411 A 1\dash byte unsigned integer representing the size
412 \addtoindexx{size of an address}
414 \addttindexx{address\_size}
415 an address on the target architecture. If the system uses
416 \addtoindexx{address space!segmented}
417 segmented addressing, this value represents the size of the
418 offset portion of an address.
420 \item \texttt{type\_signature} (8\dash byte unsigned integer) \\
421 \addtoindexx{type signature}
423 \addttindexx{type\_signature}
424 64\dash bit unique signature (see Section
425 \refersec{datarep:typesignaturecomputation})
426 of the type described in this type
429 \textit{An attribute that refers (using
430 \livelink{chap:DWFORMrefsig8}{DW\_FORM\_ref\_sig8}) to
431 the primary type contained in this
432 \addtoindex{type unit} uses this value.}
434 \item \texttt{type\_offset} (\livelink{datarep:sectionoffsetlength}{section offset}) \\
435 \addttindexx{type\_offset}
436 A 4\dash byte or 8\dash byte unsigned offset
437 \addtoindexx{section offset!in .debug\_types header}
438 relative to the beginning
439 of the \addtoindex{type unit} header.
440 This offset refers to the debugging
441 information entry that describes the type. Because the type
442 may be nested inside a namespace or other structures, and may
443 contain references to other types that have not been placed in
444 separate type units, it is not necessarily either the first or
445 the only entry in the type unit. In the \thirtytwobitdwarfformat,
446 this is a 4\dash byte unsigned length; in the \sixtyfourbitdwarfformat,
447 this is an 8\dash byte unsigned length
448 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
452 \subsection{Debugging Information Entry}
453 \label{datarep:debugginginformationentry}
455 Each debugging information entry begins with an unsigned LEB128
456 number containing the abbreviation code for the entry. This
457 code represents an entry within the abbreviations table
458 associated with the compilation unit containing this entry. The
459 abbreviation code is followed by a series of attribute values.
461 On some architectures, there are alignment constraints on
462 section boundaries. To make it easier to pad debugging
463 information sections to satisfy such constraints, the
464 abbreviation code 0 is reserved. Debugging information entries
465 consisting of only the abbreviation code 0 are considered
468 \subsection{Abbreviations Tables}
469 \label{datarep:abbreviationstables}
471 The abbreviations tables for all compilation units
472 are contained in a separate object file section called
474 As mentioned before, multiple compilation
475 units may share the same abbreviations table.
477 The abbreviations table for a single compilation unit consists
478 of a series of abbreviation declarations. Each declaration
479 specifies the tag and attributes for a particular form of
480 debugging information entry. Each declaration begins with
481 an unsigned LEB128 number representing the abbreviation
482 code itself. It is this code that appears at the beginning
483 of a debugging information entry in the
486 section. As described above, the abbreviation
487 code 0 is reserved for null debugging information entries. The
488 abbreviation code is followed by another unsigned LEB128
489 number that encodes the entry\textquoteright s tag. The encodings for the
490 tag names are given in
491 Table \refersec{tab:tagencodings}.
494 \setlength{\extrarowheight}{0.1cm}
495 \begin{longtable}{l|l}
497 \caption{Tag encodings} \label{tab:tagencodings} \\
498 \hline \bfseries Tag name&\bfseries Value\\ \hline
500 \bfseries Tag name&\bfseries Value \\ \hline
502 \hline \emph{Continued on next page}
506 \livelink{chap:DWTAGarraytype}{DW\_TAG\_array\_type} &0x01 \\
507 \livelink{chap:DWTAGclasstype}{DW\_TAG\_class\_type}&0x02 \\
508 \livelink{chap:DWTAGentrypoint}{DW\_TAG\_entry\_point}&0x03 \\
509 \livelink{chap:DWTAGenumerationtype}{DW\_TAG\_enumeration\_type}&0x04 \\
510 \livelink{chap:DWTAGformalparameter}{DW\_TAG\_formal\_parameter}&0x05 \\
511 \livelink{chap:DWTAGimporteddeclaration}{DW\_TAG\_imported\_declaration}&0x08 \\
512 \livelink{chap:DWTAGlabel}{DW\_TAG\_label}&0x0a \\
513 \livelink{chap:DWTAGlexicalblock}{DW\_TAG\_lexical\_block}&0x0b \\
514 \livelink{chap:DWTAGmember}{DW\_TAG\_member}&0x0d \\
515 \livelink{chap:DWTAGpointertype}{DW\_TAG\_pointer\_type}&0x0f \\
516 \livelink{chap:DWTAGreferencetype}{DW\_TAG\_reference\_type}&0x10 \\
517 \livelink{chap:DWTAGcompileunit}{DW\_TAG\_compile\_unit}&0x11 \\
518 \livelink{chap:DWTAGstringtype}{DW\_TAG\_string\_type}&0x12 \\
519 \livelink{chap:DWTAGstructuretype}{DW\_TAG\_structure\_type}&0x13 \\
520 \livelink{chap:DWTAGsubroutinetype}{DW\_TAG\_subroutine\_type}&0x15 \\
521 \livelink{chap:DWTAGtypedef}{DW\_TAG\_typedef}&0x16 \\
522 \livelink{chap:DWTAGuniontype}{DW\_TAG\_union\_type}&0x17 \\
523 \livelink{chap:DWTAGunspecifiedparameters}{DW\_TAG\_unspecified\_parameters}&0x18 \\
524 \livelink{chap:DWTAGvariant}{DW\_TAG\_variant}&0x19 \\
525 \livelink{chap:DWTAGcommonblock}{DW\_TAG\_common\_block}&0x1a \\
526 \livelink{chap:DWTAGcommoninclusion}{DW\_TAG\_common\_inclusion}&0x1b \\
527 \livelink{chap:DWTAGinheritance}{DW\_TAG\_inheritance}&0x1c \\
528 \livelink{chap:DWTAGinlinedsubroutine}{DW\_TAG\_inlined\_subroutine}&0x1d \\
529 \livelink{chap:DWTAGmodule}{DW\_TAG\_module}&0x1e \\
530 \livelink{chap:DWTAGptrtomembertype}{DW\_TAG\_ptr\_to\_member\_type}&0x1f \\
531 \livelink{chap:DWTAGsettype}{DW\_TAG\_set\_type}&0x20 \\
532 \livelink{chap:DWTAGsubrangetype}{DW\_TAG\_subrange\_type}&0x21 \\
533 \livelink{chap:DWTAGwithstmt}{DW\_TAG\_with\_stmt}&0x22 \\
534 \livelink{chap:DWTAGaccessdeclaration}{DW\_TAG\_access\_declaration}&0x23 \\
535 \livelink{chap:DWTAGbasetype}{DW\_TAG\_base\_type}&0x24 \\
536 \livelink{chap:DWTAGcatchblock}{DW\_TAG\_catch\_block}&0x25 \\
537 \livelink{chap:DWTAGconsttype}{DW\_TAG\_const\_type}&0x26 \\
538 \livelink{chap:DWTAGconstant}{DW\_TAG\_constant}&0x27 \\
539 \livelink{chap:DWTAGenumerator}{DW\_TAG\_enumerator}&0x28 \\
540 \livelink{chap:DWTAGfiletype}{DW\_TAG\_file\_type}&0x29 \\
541 \livelink{chap:DWTAGfriend}{DW\_TAG\_friend}&0x2a \\
542 \livelink{chap:DWTAGnamelist}{DW\_TAG\_namelist}&0x2b \\
543 \livelink{chap:DWTAGnamelistitem}{DW\_TAG\_namelist\_item}&0x2c \\
544 \livelink{chap:DWTAGpackedtype}{DW\_TAG\_packed\_type}&0x2d \\
545 \livelink{chap:DWTAGsubprogram}{DW\_TAG\_subprogram}&0x2e \\
546 \livelink{chap:DWTAGtemplatetypeparameter}{DW\_TAG\_template\_type\_parameter}&0x2f \\
547 \livelink{chap:DWTAGtemplatevalueparameter}{DW\_TAG\_template\_value\_parameter}&0x30 \\
548 \livelink{chap:DWTAGthrowntype}{DW\_TAG\_thrown\_type}&0x31 \\
549 \livelink{chap:DWTAGtryblock}{DW\_TAG\_try\_block}&0x32 \\
550 \livelink{chap:DWTAGvariantpart}{DW\_TAG\_variant\_part}&0x33 \\
551 \livelink{chap:DWTAGvariable}{DW\_TAG\_variable}&0x34 \\
552 \livelink{chap:DWTAGvolatiletype}{DW\_TAG\_volatile\_type}&0x35 \\
553 \livelink{chap:DWTAGdwarfprocedure}{DW\_TAG\_dwarf\_procedure}&0x36 \\
554 \livelink{chap:DWTAGrestricttype}{DW\_TAG\_restrict\_type}&0x37 \\
555 \livelink{chap:DWTAGinterfacetype}{DW\_TAG\_interface\_type}&0x38 \\
556 \livelink{chap:DWTAGnamespace}{DW\_TAG\_namespace}&0x39 \\
557 \livelink{chap:DWTAGimportedmodule}{DW\_TAG\_imported\_module}&0x3a \\
558 \livelink{chap:DWTAGunspecifiedtype}{DW\_TAG\_unspecified\_type}&0x3b \\
559 \livelink{chap:DWTAGpartialunit}{DW\_TAG\_partial\_unit}&0x3c \\
560 \livelink{chap:DWTAGimportedunit}{DW\_TAG\_imported\_unit}&0x3d \\
561 \livelink{chap:DWTAGcondition}{DW\_TAG\_condition}&\xiiif \\
562 \livelink{chap:DWTAGsharedtype}{DW\_TAG\_shared\_type}&0x40 \\
563 \livelink{chap:DWTAGtypeunit}{DW\_TAG\_type\_unit} &0x41 \\
564 \livelink{chap:DWTAGrvaluereferencetype}{DW\_TAG\_rvalue\_reference\_type} &0x42 \\
565 \livelink{chap:DWTAGtemplatealias}{DW\_TAG\_template\_alias} &0x43 \\
566 \DWTAGcoarraytypeLL &0x44 \\
567 \DWTAGgenericsubrangeLL &0x45 \\
568 \livelink{chap:DWXXXlohiuser}{DW\_TAG\_lo\_user}&0x4080 \\
569 \livelink{chap:DWXXXlohiuser}{DW\_TAG\_hi\_user}&\xffff \\
573 Following the tag encoding is a 1\dash byte value that determines
574 whether a debugging information entry using this abbreviation
575 has child entries or not. If the value is
576 \livetarg{chap:DWCHILDRENyes}{DW\_CHILDREN\_yes},
577 the next physically succeeding entry of any debugging
578 information entry using this abbreviation is the first
579 child of that entry. If the 1\dash byte value following the
580 abbreviation\textquoteright s tag encoding is
581 \livetarg{chap:DWCHILDRENno}{DW\_CHILDREN\_no}, the next
582 physically succeeding entry of any debugging information entry
583 using this abbreviation is a sibling of that entry. (Either
584 the first child or sibling entries may be null entries). The
585 encodings for the child determination byte are given in
586 Table \refersec{tab:childdeterminationencodings}
588 Section \refersec{chap:relationshipofdebugginginformationentries},
589 each chain of sibling entries is terminated by a null entry.)
593 \setlength{\extrarowheight}{0.1cm}
594 \begin{longtable}{l|l}
595 \caption{Child determination encodings}
596 \label{tab:childdeterminationencodings}
597 \addtoindexx{Child determination encodings} \\
598 \hline \bfseries Children determination name&\bfseries Value \\ \hline
600 \bfseries Children determination name&\bfseries Value \\ \hline
602 \hline \emph{Continued on next page}
606 \livelink{chap:DWCHILDRENno}{DW\_CHILDREN\_no}&0x00 \\
607 \livelink{chap:DWCHILDRENyes}{DW\_CHILDREN\_yes}&0x01 \\ \hline
612 Finally, the child encoding is followed by a series of
613 attribute specifications. Each attribute specification
614 consists of two parts. The first part is an unsigned LEB128
615 number representing the attribute\textquoteright s name. The second part
616 is an unsigned LEB128 number representing the attribute\textquoteright s
617 form. The series of attribute specifications ends with an
618 entry containing 0 for the name and 0 for the form.
621 \livetarg{chap:DWFORMindirect}{DW\_FORM\_indirect} is a special case. For
622 attributes with this form, the attribute value itself in the
625 section begins with an unsigned
626 LEB128 number that represents its form. This allows producers
627 to choose forms for particular attributes
628 \addtoindexx{abbreviations table!dynamic forms in}
630 without having to add a new entry to the abbreviations table.
632 The abbreviations for a given compilation unit end with an
633 entry consisting of a 0 byte for the abbreviation code.
636 Appendix \refersec{app:compilationunitsandabbreviationstableexample}
637 for a depiction of the organization of the
638 debugging information.}
641 \subsection{Attribute Encodings}
642 \label{datarep:attributeencodings}
644 The encodings for the attribute names are given in
645 Table \refersec{tab:attributeencodings}.
647 The attribute form governs how the value of the attribute is
648 encoded. There are nine classes of form, listed below. Each
649 class is a set of forms which have related representations
650 and which are given a common interpretation according to the
651 attribute in which the form is used.
653 Form \livetarg{chap:DWFORMsecoffset}{DW\_FORM\_sec\_offset}
655 \addtoindexx{rangelistptr class}
657 \addtoindexx{macptr class}
659 \addtoindexx{loclistptr class}
661 \addtoindexx{lineptr class}
662 namely \livelink{chap:classlineptr}{lineptr},
663 \livelink{chap:classloclistptr}{loclistptr},
664 \livelink{chap:classmacptr}{macptr} or
665 \livelink{chap:classrangelistptr}{rangelistptr}; the list
666 of classes allowed by the applicable attribute in
667 Table \refersec{tab:attributeencodings}
668 determines the class of the form.
670 \textit{In DWARF V3 the forms \livelink{chap:DWFORMdata4}{DW\_FORM\_data4} and
671 \livelink{chap:DWFORMdata8}{DW\_FORM\_data8} were
672 \addtoindexx{lineptr class}
674 \addtoindexx{rangelistptr class}
676 \addtoindexx{macptr class}
678 \addtoindexx{loclistptr class}
679 class constant \addtoindexx{constant class}
680 or one of the classes
681 \livelink{chap:classlineptr}{lineptr},
682 \livelink{chap:classloclistptr}{loclistptr},
683 \livelink{chap:classmacptr}{macptr} or
684 \livelink{chap:classrangelistptr}{rangelistptr}, depending on context. In
686 \livelink{chap:DWFORMdata4}{DW\_FORM\_data4} and
687 \livelink{chap:DWFORMdata8}{DW\_FORM\_data8} are members of class
688 constant in all cases.
690 \livelink{chap:DWFORMsecoffset}{DW\_FORM\_sec\_offset} replaces
691 their usage for the other classes.}
693 Each possible form belongs to one or more of the following classes:
696 \item \livelinki{chap:classaddress}{address}{address class} \\
697 \livetarg{datarep:classaddress}{}
698 Represented as an object of appropriate size to hold an
699 address on the target machine
700 (\livetarg{chap:DWFORMaddr}{DW\_FORM\_addr}).
702 encoded in the compilation unit header
703 (see Section \refersec{datarep:compilationunitheader}).
704 This address is relocatable in a relocatable object file and
705 is relocated in an executable file or shared object.
708 \item \livelink{chap:classblock}{block} \\
709 \livetarg{datarep:classblock}{}
710 Blocks come in four forms:
712 \begin{myindentpara}{1cm}
713 A 1\dash byte length followed by 0 to 255 contiguous information
714 bytes (\livetarg{chap:DWFORMblock1}{DW\_FORM\_block1}).
717 \begin{myindentpara}{1cm}
718 A 2\dash byte length followed by 0 to 65,535 contiguous information
719 bytes (\livetarg{chap:DWFORMblock2}{DW\_FORM\_block2}).
722 \begin{myindentpara}{1cm}
723 A 4\dash byte length followed by 0 to 4,294,967,295 contiguous
724 information bytes (\livetarg{chap:DWFORMblock4}{DW\_FORM\_block4}).
727 \begin{myindentpara}{1cm}
728 An unsigned LEB128 length followed by the number of bytes
729 specified by the length (\livetarg{chap:DWFORMblock}{DW\_FORM\_block}).
732 In all forms, the length is the number of information bytes
733 that follow. The information bytes may contain any mixture
734 of relocated (or relocatable) addresses, references to other
735 debugging information entries or data bytes.
737 \item \livelinki{chap:classconstant}{constant}{constant class} \\
738 \livetarg{datarep:classconstant}{}
739 There are six forms of constants. There are fixed length
740 constant data forms for one, two, four and eight byte values
742 \livetarg{chap:DWFORMdata1}{DW\_FORM\_data1},
743 \livetarg{chap:DWFORMdata2}{DW\_FORM\_data2},
744 \livetarg{chap:DWFORMdata4}{DW\_FORM\_data4},
745 and \livetarg{chap:DWFORMdata8}{DW\_FORM\_data8}).
746 There are also variable length constant
747 data forms encoded using LEB128 numbers (see below). Both
748 signed (\livetarg{chap:DWFORMsdata}{DW\_FORM\_sdata}) and unsigned
749 (\livetarg{chap:DWFORMudata}{DW\_FORM\_udata}) variable
750 length constants are available
752 The data in \livelink{chap:DWFORMdata1}{DW\_FORM\_data1},
753 \livelink{chap:DWFORMdata2}{DW\_FORM\_data2},
754 \livelink{chap:DWFORMdata4}{DW\_FORM\_data4} and
755 \livelink{chap:DWFORMdata8}{DW\_FORM\_data8}
756 can be anything. Depending on context, it may
757 be a signed integer, an unsigned integer, a floating\dash point
758 constant, or anything else. A consumer must use context to
759 know how to interpret the bits, which if they are target
760 machine data (such as an integer or floating point constant)
761 will be in target machine byte\dash order.
763 \textit{If one of the \livetarg{chap:DWFORMdata}{DW\_FORM\_data}\textless n\textgreater
764 forms is used to represent a
765 signed or unsigned integer, it can be hard for a consumer
766 to discover the context necessary to determine which
767 interpretation is intended. Producers are therefore strongly
768 encouraged to use \livelink{chap:DWFORMsdata}{DW\_FORM\_sdata} or
769 \livelink{chap:DWFORMudata}{DW\_FORM\_udata} for signed and
770 unsigned integers respectively, rather than
771 \livelink{chap:DWFORMdata}{DW\_FORM\_data}\textless n\textgreater.}
774 \item \livelinki{chap:classexprloc}{exprloc}{exprloc class} \\
775 \livetarg{datarep:classexprloc}{}
776 This is an unsigned LEB128 length followed by the
777 number of information bytes specified by the length
778 (\livetarg{chap:DWFORMexprloc}{DW\_FORM\_exprloc}).
779 The information bytes contain a DWARF expression
780 (see Section \refersec{chap:dwarfexpressions})
781 or location description
782 (see Section \refersec{chap:locationdescriptions}).
784 \item \livelinki{chap:classflag}{flag}{flag class} \\
785 \livetarg{datarep:classflag}{}
786 A flag \addtoindexx{flag class}
787 is represented explicitly as a single byte of data
788 (\livetarg{chap:DWFORMflag}{DW\_FORM\_flag}) or
789 implicitly (\livetarg{chap:DWFORMflagpresent}{DW\_FORM\_flag\_present}).
791 first case, if the \nolink{flag} has value zero, it indicates the
792 absence of the attribute; if the \nolink{flag} has a non\dash zero value,
793 it indicates the presence of the attribute. In the second
794 case, the attribute is implicitly indicated as present, and
795 no value is encoded in the debugging information entry itself.
797 \item \livelinki{chap:classlineptr}{lineptr}{lineptr class} \\
798 \livetarg{datarep:classlineptr}{}
799 This is an offset into
800 \addtoindexx{section offset!in class lineptr value}
802 \dotdebugline{} section
803 (\livelink{chap:DWFORMsecoffset}{DW\_FORM\_sec\_offset}).
804 It consists of an offset from the beginning of the
806 section to the first byte of
807 the data making up the line number list for the compilation
809 It is relocatable in a relocatable object file, and
810 relocated in an executable or shared object. In the
811 \thirtytwobitdwarfformat, this offset is a 4\dash byte unsigned value;
812 in the \sixtyfourbitdwarfformat, it is an 8\dash byte unsigned value
813 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
816 \item \livelinki{chap:classloclistptr}{loclistptr}{loclistptr class} \\
817 \livetarg{datarep:classloclistptr}{}
818 This is an offset into the
821 (\livelink{chap:DWFORMsecoffset}{DW\_FORM\_sec\_offset}).
822 It consists of an offset from the
823 \addtoindexx{section offset!in class loclistptr value}
826 section to the first byte of
827 the data making up the
828 \addtoindex{location list} for the compilation unit.
829 It is relocatable in a relocatable object file, and
830 relocated in an executable or shared object. In the
831 \thirtytwobitdwarfformat, this offset is a 4\dash byte unsigned value;
832 in the \sixtyfourbitdwarfformat, it is an 8\dash byte unsigned value
833 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
836 \item \livelinki{chap:classmacptr}{macptr}{macptr class} \\
837 \livetarg{datarep:classmacptr}{}
839 \addtoindexx{section offset!in class macptr value}
841 \dotdebugmacinfo{} section
842 (\livelink{chap:DWFORMsecoffset}{DW\_FORM\_sec\_offset}).
843 It consists of an offset from the
844 beginning of the \dotdebugmacinfo{}
845 section to the first byte of
846 the data making up the macro information list for the compilation
848 It is relocatable in a relocatable object file, and
849 relocated in an executable or shared object. In the
850 \thirtytwobitdwarfformat, this offset is a 4\dash byte unsigned value;
851 in the \sixtyfourbitdwarfformat, it is an 8\dash byte unsigned value
852 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
855 \item \livelinki{chap:classrangelistptr}{rangelistptr}{rangelistptr class} \\
856 \livetarg{datarep:classrangelistptr}{}
858 \addtoindexx{section offset!in class rangelistptr value}
859 offset into the \dotdebugranges{} section
860 (\livelink{chap:DWFORMsecoffset}{DW\_FORM\_sec\_offset}).
862 offset from the beginning of the
863 \dotdebugranges{} section
864 to the beginning of the non\dash contiguous address ranges
865 information for the referencing entity.
867 a relocatable object file, and relocated in an executable or
868 shared object. In the \thirtytwobitdwarfformat, this offset
869 is a 4\dash byte unsigned value; in the 64\dash bit DWARF
870 format, it is an 8\dash byte unsigned value (see Section
871 \refersec{datarep:32bitand64bitdwarfformats}).
874 \textit{Because classes \livelink{chap:classlineptr}{lineptr},
875 \livelink{chap:classloclistptr}{loclistptr},
876 \livelink{chap:classmacptr}{macptr} and
877 \livelink{chap:classrangelistptr}{rangelistptr}
878 share a common representation, it is not possible for an
879 attribute to allow more than one of these classes}
883 \item \livelinki{chap:classreference}{reference}{reference class} \\
884 \livetarg{datarep:classreference}{}
885 There are three types of reference.
888 \addtoindexx{reference class}
889 first type of reference can identify any debugging
890 information entry within the containing unit.
893 \addtoindexx{section offset!in class reference value}
894 offset from the first byte of the compilation
895 header for the compilation unit containing the reference. There
896 are five forms for this type of reference. There are fixed
897 length forms for one, two, four and eight byte offsets
898 (respectively, \livetarg{chap:DWFORMref1}{DW\_FORM\_ref1},
899 \livetarg{chap:DWFORMref2}{DW\_FORM\_ref2},
900 \livetarg{chap:DWFORMref4}{DW\_FORM\_ref4},
901 and \livetarg{chap:DWFORMref8}{DW\_FORM\_ref8}).
902 There is also an unsigned variable
903 length offset encoded form that uses unsigned LEB128 numbers
904 (\livetarg{chap:DWFORMrefudata}{DW\_FORM\_ref\_udata}).
905 Because this type of reference is within
906 the containing compilation unit no relocation of the value
909 The second type of reference can identify any debugging
910 information entry within a
911 \dotdebuginfo{} section; in particular,
912 it may refer to an entry in a different compilation unit
913 from the unit containing the reference, and may refer to an
914 entry in a different shared object. This type of reference
915 (\livetarg{chap:DWFORMrefaddr}{DW\_FORM\_ref\_addr})
916 is an offset from the beginning of the
918 section of the target executable or shared object;
919 it is relocatable in a relocatable object file and frequently
920 relocated in an executable file or shared object. For
921 references from one shared object or static executable file
922 to another, the relocation and identification of the target
923 object must be performed by the consumer. In the
924 \thirtytwobitdwarfformat, this offset is a 4\dash byte unsigned value;
925 in the \sixtyfourbitdwarfformat, it is an 8\dash byte
927 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
929 \textit{A debugging information entry that may be referenced by
930 another compilation unit using
931 \livelink{chap:DWFORMrefaddr}{DW\_FORM\_ref\_addr} must have a
932 global symbolic name.}
934 \textit{For a reference from one executable or shared object to
935 another, the reference is resolved by the debugger to identify
936 the shared object or executable and the offset into that
937 object\textquoteright s \dotdebuginfo{}
938 section in the same fashion as the run
939 time loader, either when the debug information is first read,
940 or when the reference is used.}
942 The third type of reference can identify any debugging
943 information type entry that has been placed in its own
944 \addtoindex{type unit}. This type of
945 reference (\livetarg{chap:DWFORMrefsig8}{DW\_FORM\_ref\_sig8}) is the
946 \addtoindexx{type signature}
947 64\dash bit type signature
948 (see Section \refersec{datarep:typesignaturecomputation})
952 \textit{The use of compilation unit relative references will reduce the
953 number of link\dash time relocations and so speed up linking. The
954 use of the second and third type of reference allows for the
955 sharing of information, such as types, across compilation
958 \textit{A reference to any kind of compilation unit identifies the
959 debugging information entry for that unit, not the preceding
962 \item \livelinki{chap:classstring}{string}{string class} \\
963 \livetarg{datarep:classstring}{}
964 A string is a sequence of contiguous non\dash null bytes followed by
966 \addtoindexx{string class}
967 A string may be represented immediately in the
968 debugging information entry itself
969 (\livetarg{chap:DWFORMstring}{DW\_FORM\_string}), or may
971 \addtoindexx{section offset!in class string value}
972 offset into a string table contained in
973 the \dotdebugstr{} section of the object file
974 (\livetarg{chap:DWFORMstrp}{DW\_FORM\_strp}). In
975 the \thirtytwobitdwarfformat, the representation of a
976 \livelink{chap:DWFORMstrp}{DW\_FORM\_strp}
977 value is a 4\dash byte unsigned offset; in the \sixtyfourbitdwarfformat,
978 it is an 8\dash byte unsigned offset
979 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
981 If the \livelink{chap:DWATuseUTF8}{DW\_AT\_use\_UTF8}
982 \addtoindexx{use UTF8 attribute}\addtoindexx{UTF-8} attribute is specified for the
983 compilation unit entry, string values are encoded using the
984 UTF\dash 8 (\addtoindex{Unicode} Transformation Format\dash 8) from the Universal
985 Character Set standard (ISO/IEC 10646\dash 1:1993). Otherwise,
986 the string representation is unspecified.
988 \textit{The \addtoindex{Unicode} Standard Version 3 is fully compatible with
989 ISO/IEC 10646\dash 1:1993. It contains all the same characters
990 and encoding points as ISO/IEC 10646, as well as additional
991 information about the characters and their use.}
993 \textit{Earlier versions of DWARF did not specify the representation
994 of strings; for compatibility, this version also does
995 not. However, the UTF\dash 8 representation is strongly recommended.}
999 In no case does an attribute use
1000 \addtoindexx{rangelistptr class}
1002 \addtoindexx{loclistptr class}
1004 \addtoindexx{lineptr class}
1006 \addtoindexx{macptr class}
1007 classes \livelink{chap:classlineptr}{lineptr},
1008 \livelink{chap:classloclistptr}{loclistptr}, \livelink{chap:classmacptr}{macptr} or
1009 \livelink{chap:classrangelistptr}{rangelistptr} to point into either the
1010 \dotdebuginfo{} or \dotdebugstr{} section.
1012 The form encodings are listed in
1013 Table \refersec{tab:attributeformencodings}.
1017 \setlength{\extrarowheight}{0.1cm}
1018 \begin{longtable}{l|l|l}
1019 \caption{Attribute encodings}
1020 \label{tab:attributeencodings}
1021 \addtoindexx{attribute encodings} \\
1022 \hline \bfseries Attribute name&\bfseries Value &\bfseries Classes \\ \hline
1024 \bfseries Attribute name&\bfseries Value &\bfseries Classes\\ \hline
1026 \hline \emph{Continued on next page}
1028 \hline \ddag\ \textit{New in DWARF Version 5}
1030 \livelink{chap:DWATsibling}{DW\_AT\_sibling}&0x01&\livelink{chap:classreference}{reference}
1031 \addtoindexx{sibling attribute!encoding} \\
1032 \livelink{chap:DWATlocation}{DW\_AT\_location}&0x02&\livelink{chap:classexprloc}{exprloc},
1033 \livelink{chap:classloclistptr}{loclistptr}\addtoindexx{location attribute!encoding} \\
1034 \livelink{chap:DWATname}{DW\_AT\_name}&0x03&\livelink{chap:classstring}{string}
1035 \addtoindexx{name attribute!encoding} \\
1036 \livelink{chap:DWATordering}{DW\_AT\_ordering}&0x09&\livelink{chap:classconstant}{constant}
1037 \addtoindexx{ordering attribute!encoding} \\
1038 \livelink{chap:DWATbytesize}{DW\_AT\_byte\_size}&0x0b&\livelink{chap:classconstant}{constant}, \livelink{chap:classexprloc}{exprloc},
1039 \livelink{chap:classreference}{reference} \addtoindexx{byte size attribute!encoding} \\
1040 \livelink{chap:DWATbitoffset}{DW\_AT\_bit\_offset}&0x0c&\livelink{chap:classconstant}{constant},
1041 \livelink{chap:classexprloc}{exprloc}, \livelink{chap:classreference}{reference} \addtoindexx{bit offset attribute!encoding} \\
1042 \livelink{chap:DWATbitsize}{DW\_AT\_bit\_size}&0x0d&\livelink{chap:classconstant}{constant},
1043 \livelink{chap:classexprloc}{exprloc}, \livelink{chap:classreference}{reference} \addtoindexx{bit size attribute!encoding} \\
1044 \livelink{chap:DWATstmtlist}{DW\_AT\_stmt\_list}&0x10&\livelink{chap:classlineptr}{lineptr}
1045 \addtoindexx{statement list attribute!encoding} \\
1046 \livelink{chap:DWATlowpc}{DW\_AT\_low\_pc}&0x11&\livelink{chap:classaddress}{address}
1047 \addtoindexx{low PC attribute!encoding} \\
1048 \livelink{chap:DWAThighpc}{DW\_AT\_high\_pc}&0x12&\livelink{chap:classaddress}{address}, \livelink{chap:classconstant}{constant}
1049 \addtoindexx{high PC attribute!encoding} \\
1050 \livelink{chap:DWATlanguage}{DW\_AT\_language}&0x13&\livelink{chap:classconstant}{constant}
1051 \addtoindexx{language attribute!encoding} \\
1052 \livelink{chap:DWATdiscr}{DW\_AT\_discr}&0x15&\livelink{chap:classreference}{reference}
1053 \addtoindexx{discriminant attribute!encoding} \\
1054 \livelink{chap:DWATdiscrvalue}{DW\_AT\_discr\_value}&0x16&\livelink{chap:classconstant}{constant}
1055 \addtoindexx{discriminant value attribute!encoding} \\
1056 \livelink{chap:DWATvisibility}{DW\_AT\_visibility}&0x17&\livelink{chap:classconstant}{constant}
1057 \addtoindexx{visibility attribute!encoding} \\
1058 \livelink{chap:DWATimport}{DW\_AT\_import}&0x18&\livelink{chap:classreference}{reference}
1059 \addtoindexx{import attribute!encoding} \\
1060 \livelink{chap:DWATstringlength}{DW\_AT\_string\_length}&0x19&\livelink{chap:classexprloc}{exprloc},
1061 \livelink{chap:classloclistptr}{loclistptr} \addtoindexx{string length attribute!encoding} \\
1062 \livelink{chap:DWATcommonreference}{DW\_AT\_common\_reference}&0x1a&\livelink{chap:classreference}{reference}
1063 \addtoindexx{common reference attribute!encoding} \\
1064 \livelink{chap:DWATcompdir}{DW\_AT\_comp\_dir}&0x1b&\livelink{chap:classstring}{string}
1065 \addtoindexx{compilation directory attribute!encoding} \\
1066 \livelink{chap:DWATconstvalue}{DW\_AT\_const\_value}&0x1c&\livelink{chap:classblock}{block}, \livelink{chap:classconstant}{constant}, \livelink{chap:classstring}{string}
1067 \addtoindexx{constant value attribute!encoding} \\
1068 \livelink{chap:DWATcontainingtype}{DW\_AT\_containing\_type}&0x1d&\livelink{chap:classreference}{reference}
1069 \addtoindexx{containing type attribute!encoding} \\
1070 \livelink{chap:DWATdefaultvalue}{DW\_AT\_default\_value}&0x1e&\livelink{chap:classreference}{reference}
1071 \addtoindexx{default value attribute!encoding} \\
1072 \livelink{chap:DWATinline}{DW\_AT\_inline}&0x20&\livelink{chap:classconstant}{constant}
1073 \addtoindexx{inline attribute!encoding} \\
1074 \livelink{chap:DWATisoptional}{DW\_AT\_is\_optional}&0x21&\livelink{chap:classflag}{flag}
1075 \addtoindexx{is optional attribute!encoding} \\
1076 \livelink{chap:DWATlowerbound}{DW\_AT\_lower\_bound}&0x22&\livelink{chap:classconstant}{constant},
1077 \livelink{chap:classexprloc}{exprloc}, \livelink{chap:classreference}{reference} \addtoindexx{lower bound attribute!encoding} \\
1078 \livelink{chap:DWATproducer}{DW\_AT\_producer}&0x25&\livelink{chap:classstring}{string} \addtoindexx{producer attribute!encoding} \\
1079 \livelink{chap:DWATprototyped}{DW\_AT\_prototyped}&0x27&\livelink{chap:classflag}{flag}
1080 \addtoindexx{prototyped attribute!encoding} \\
1081 \livelink{chap:DWATreturnaddr}{DW\_AT\_return\_addr}&0x2a&\livelink{chap:classexprloc}{exprloc},
1082 \livelink{chap:classloclistptr}{loclistptr} \addtoindexx{return address attribute!encoding} \\
1083 % FIXME: lower case , not Constant
1084 \livelink{chap:DWATstartscope}{DW\_AT\_start\_scope}&0x2c&\livelink{chap:classconstant}{constant},
1085 \livelink{chap:classrangelistptr}{rangelistptr} \addtoindexx{start scope attribute!encoding} \\
1086 \livelink{chap:DWATbitstride}{DW\_AT\_bit\_stride}&0x2e&\livelink{chap:classconstant}{constant},
1087 \livelink{chap:classexprloc}{exprloc}, \livelink{chap:classreference}{reference} \addtoindexx{bit stride attribute!encoding} \\
1088 \livelink{chap:DWATupperbound}{DW\_AT\_upper\_bound}&0x2f&\livelink{chap:classconstant}{constant},
1089 \livelink{chap:classexprloc}{exprloc}, \livelink{chap:classreference}{reference} \addtoindexx{upper bound attribute!encoding} \\
1090 \livelink{chap:DWATabstractorigin}{DW\_AT\_abstract\_origin}&0x31&\livelink{chap:classreference}{reference}
1091 \addtoindexx{abstract origin attribute!encoding} \\
1092 \livelink{chap:DWATaccessibility}{DW\_AT\_accessibility}&0x32&\livelink{chap:classconstant}{constant}
1093 \addtoindexx{accessibility attribute!encoding} \\
1094 \livelink{chap:DWATaddressclass}{DW\_AT\_address\_class}&0x33&\livelink{chap:classconstant}{constant}
1095 \addtoindexx{address class attribute!encoding} \\
1096 \livelink{chap:DWATartificial}{DW\_AT\_artificial}&0x34&\livelink{chap:classflag}{flag}
1097 \addtoindexx{artificial attribute!encoding} \\
1098 \livelink{chap:DWATbasetypes}{DW\_AT\_base\_types}&0x35&\livelink{chap:classreference}{reference}
1099 \addtoindexx{base types attribute!encoding} \\
1100 \livelink{chap:DWATcallingconvention}{DW\_AT\_calling\_convention}&0x36&\livelink{chap:classconstant}{constant}
1101 \addtoindexx{calling convention attribute!encoding} \\
1102 \livelink{chap:DWATcount}{DW\_AT\_count}&0x37&\livelink{chap:classconstant}{constant}, \livelink{chap:classexprloc}{exprloc}, \livelink{chap:classreference}{reference}
1103 \addtoindexx{count attribute!encoding} \\
1104 \livelink{chap:DWATdatamemberlocation}{DW\_AT\_data\_member\_location}&0x38&\livelink{chap:classconstant}{constant},
1105 \livelink{chap:classexprloc}{exprloc}, \livelink{chap:classloclistptr}{loclistptr}
1106 \addtoindexx{data member attribute!encoding} \\
1107 \livelink{chap:DWATdeclcolumn}{DW\_AT\_decl\_column}&0x39&\livelink{chap:classconstant}{constant}
1108 \addtoindexx{declaration column attribute!encoding} \\
1109 \livelink{chap:DWATdeclfile}{DW\_AT\_decl\_file}&0x3a&\livelink{chap:classconstant}{constant}
1110 \addtoindexx{declaration file attribute!encoding} \\
1111 \livelink{chap:DWATdeclline}{DW\_AT\_decl\_line}&0x3b&\livelink{chap:classconstant}{constant}
1112 \addtoindexx{declaration line attribute!encoding} \\
1113 \livelink{chap:DWATdeclaration}{DW\_AT\_declaration}&0x3c&\livelink{chap:classflag}{flag}
1114 \addtoindexx{declaration attribute!encoding} \\
1115 \livelink{chap:DWATdiscrlist}{DW\_AT\_discr\_list}&0x3d&\livelink{chap:classblock}{block}
1116 \addtoindexx{discriminant list attribute!encoding} \\
1117 \livelink{chap:DWATencoding}{DW\_AT\_encoding}&0x3e&\livelink{chap:classconstant}{constant}
1118 \addtoindexx{encoding attribute!encoding} \\
1119 \livelink{chap:DWATexternal}{DW\_AT\_external}&\xiiif&\livelink{chap:classflag}{flag}
1120 \addtoindexx{external attribute!encoding} \\
1121 \livelink{chap:DWATframebase}{DW\_AT\_frame\_base}&0x40&\livelink{chap:classexprloc}{exprloc},
1122 \livelink{chap:classloclistptr}{loclistptr} \addtoindexx{frame base attribute!encoding} \\
1123 \livelink{chap:DWATfriend}{DW\_AT\_friend}&0x41&\livelink{chap:classreference}{reference}
1124 \addtoindexx{friend attribute!encoding} \\
1125 \livelink{chap:DWATidentifiercase}{DW\_AT\_identifier\_case}&0x42&\livelink{chap:classconstant}{constant}
1126 \addtoindexx{identifier case attribute!encoding} \\
1127 \livelink{chap:DWATmacroinfo}{DW\_AT\_macro\_info}&0x43&\livelink{chap:classmacptr}{macptr}
1128 \addtoindexx{macro information attribute!encoding} \\
1129 \livelink{chap:DWATnamelistitem}{DW\_AT\_namelist\_item}&0x44&\livelink{chap:classreference}{reference}
1130 \addtoindexx{name list item attribute!encoding} \\
1131 \livelink{chap:DWATpriority}{DW\_AT\_priority}&0x45&\livelink{chap:classreference}{reference}
1132 \addtoindexx{priority attribute!encoding} \\
1133 \livelink{chap:DWATsegment}{DW\_AT\_segment}&0x46&\livelink{chap:classexprloc}{exprloc},
1134 \livelink{chap:classloclistptr}{loclistptr} \addtoindexx{segment attribute!encoding} \\
1135 \livelink{chap:DWATspecification}{DW\_AT\_specification}&0x47&\livelink{chap:classreference}{reference}
1136 \addtoindexx{specification attribute!encoding} \\
1137 \livelink{chap:DWATstaticlink}{DW\_AT\_static\_link}&0x48&\livelink{chap:classexprloc}{exprloc},
1138 \livelink{chap:classloclistptr}{loclistptr} \addtoindexx{static link attribute!encoding} \\
1139 \livelink{chap:DWATtype}{DW\_AT\_type}&0x49&\livelink{chap:classreference}{reference}
1140 \addtoindexx{type attribute!encoding} \\
1141 \livelink{chap:DWATuselocation}{DW\_AT\_use\_location}&0x4a&\livelink{chap:classexprloc}{exprloc},
1142 \livelink{chap:classloclistptr}{loclistptr} \addtoindexx{location list attribute!encoding} \\
1143 \livelink{chap:DWATvariableparameter}{DW\_AT\_variable\_parameter}&0x4b&\livelink{chap:classflag}{flag}
1144 \addtoindexx{variable parameter attribute!encoding} \\
1145 \livelink{chap:DWATvirtuality}{DW\_AT\_virtuality}&0x4c&\livelink{chap:classconstant}{constant}
1146 \addtoindexx{virtuality attribute!encoding} \\
1147 \livelink{chap:DWATvtableelemlocation}{DW\_AT\_vtable\_elem\_location}&0x4d&\livelink{chap:classexprloc}{exprloc},
1148 \livelink{chap:classloclistptr}{loclistptr} \addtoindexx{vtable element location attribute!encoding} \\
1149 \livelink{chap:DWATallocated}{DW\_AT\_allocated}&0x4e&\livelink{chap:classconstant}{constant}, \livelink{chap:classexprloc}{exprloc},
1150 \livelink{chap:classreference}{reference} \addtoindexx{allocated attribute!encoding} \\
1151 \livelink{chap:DWATassociated}{DW\_AT\_associated}&0x4f&\livelink{chap:classconstant}{constant}, \livelink{chap:classexprloc}{exprloc},
1152 \livelink{chap:classreference}{reference} \addtoindexx{associated attribute!encoding} \\
1153 \livelink{chap:DWATdatalocation}{DW\_AT\_data\_location}&0x50&\livelink{chap:classexprloc}{exprloc}
1154 \addtoindexx{data location attribute!encoding} \\
1155 \livelink{chap:DWATbytestride}{DW\_AT\_byte\_stride}&0x51&\livelink{chap:classconstant}{constant}, \livelink{chap:classexprloc}{exprloc},
1156 \livelink{chap:classreference}{reference} \addtoindexx{byte stride attribute!encoding} \\
1157 \livelink{chap:DWATentrypc}{DW\_AT\_entry\_pc}&0x52&\livelink{chap:classaddress}{address}
1158 \addtoindexx{entry pc attribute!encoding} \\
1159 \livelink{chap:DWATuseUTF8}{DW\_AT\_use\_UTF8}&0x53&\livelink{chap:classflag}{flag}
1160 \addtoindexx{use UTF8 attribute!encoding}\addtoindexx{UTF-8} \\
1161 \livelink{chap:DWATextension}{DW\_AT\_extension}&0x54&\livelink{chap:classreference}{reference}
1162 \addtoindexx{extension attribute!encoding} \\
1163 \livelink{chap:DWATranges}{DW\_AT\_ranges}&0x55&\livelink{chap:classrangelistptr}{rangelistptr}
1164 \addtoindexx{ranges attribute!encoding} \\
1165 \livelink{chap:DWATtrampoline}{DW\_AT\_trampoline}&0x56&\livelink{chap:classaddress}{address}, \livelink{chap:classflag}{flag},
1166 \livelink{chap:classreference}{reference}, \livelink{chap:classstring}{string} \addtoindexx{trampoline attribute!encoding} \\
1167 \livelink{chap:DWATcallcolumn}{DW\_AT\_call\_column}&0x57&\livelink{chap:classconstant}{constant}
1168 \addtoindexx{call column attribute!encoding} \\
1169 \livelink{chap:DWATcallfile}{DW\_AT\_call\_file}&0x58&\livelink{chap:classconstant}{constant}
1170 \addtoindexx{call file attribute!encoding} \\
1171 \livelink{chap:DWATcallline}{DW\_AT\_call\_line}&0x59&\livelink{chap:classconstant}{constant}
1172 \addtoindexx{call line attribute!encoding} \\
1173 \livelink{chap:DWATdescription}{DW\_AT\_description}&0x5a&\livelink{chap:classstring}{string}
1174 \addtoindexx{description attribute!encoding} \\
1175 \livelink{chap:DWATbinaryscale}{DW\_AT\_binary\_scale}&0x5b&\livelink{chap:classconstant}{constant}
1176 \addtoindexx{binary scale attribute!encoding} \\
1177 \livelink{chap:DWATdecimalscale}{DW\_AT\_decimal\_scale}&0x5c&\livelink{chap:classconstant}{constant}
1178 \addtoindexx{decimal scale attribute!encoding} \\
1179 \livelink{chap:DWATsmall}{DW\_AT\_small} &0x5d&\livelink{chap:classreference}{reference}
1180 \addtoindexx{small attribute!encoding} \\
1181 \livelink{chap:DWATdecimalsign}{DW\_AT\_decimal\_sign}&0x5e&\livelink{chap:classconstant}{constant}
1182 \addtoindexx{decimal scale attribute!encoding} \\
1183 \livelink{chap:DWATdigitcount}{DW\_AT\_digit\_count}&0x5f&\livelink{chap:classconstant}{constant}
1184 \addtoindexx{digit count attribute!encoding} \\
1185 \livelink{chap:DWATpicturestring}{DW\_AT\_picture\_string}&0x60&\livelink{chap:classstring}{string}
1186 \addtoindexx{picture string attribute!encoding} \\
1187 \livelink{chap:DWATmutable}{DW\_AT\_mutable}&0x61&\livelink{chap:classflag}{flag}
1188 \addtoindexx{mutable attribute!encoding} \\
1189 \livelink{chap:DWATthreadsscaled}{DW\_AT\_threads\_scaled}&0x62&\livelink{chap:classflag}{flag}
1190 \addtoindexx{thread scaled attribute!encoding} \\
1191 \livelink{chap:DWATexplicit}{DW\_AT\_explicit}&0x63&\livelink{chap:classflag}{flag}
1192 \addtoindexx{explicit attribute!encoding} \\
1193 \livelink{chap:DWATobjectpointer}{DW\_AT\_object\_pointer}&0x64&\livelink{chap:classreference}{reference}
1194 \addtoindexx{object pointer attribute!encoding} \\
1195 \livelink{chap:DWATendianity}{DW\_AT\_endianity}&0x65&\livelink{chap:classconstant}{constant}
1196 \addtoindexx{endianity attribute!encoding} \\
1197 \livelink{chap:DWATelemental}{DW\_AT\_elemental}&0x66&\livelink{chap:classflag}{flag}
1198 \addtoindexx{elemental attribute!encoding} \\
1199 \livelink{chap:DWATpure}{DW\_AT\_pure}&0x67&\livelink{chap:classflag}{flag}
1200 \addtoindexx{pure attribute!encoding} \\
1201 \livelink{chap:DWATrecursive}{DW\_AT\_recursive}&0x68&\livelink{chap:classflag}{flag}
1202 \addtoindexx{recursive attribute!encoding} \\
1203 \livelink{chap:DWATsignature}{DW\_AT\_signature} &0x69&\livelink{chap:classreference}{reference}
1204 \addtoindexx{signature attribute!encoding} \\
1205 \livelink{chap:DWATmainsubprogram}{DW\_AT\_main\_subprogram} &0x6a&\livelink{chap:classflag}{flag}
1206 \addtoindexx{main subprogram attribute!encoding} \\
1207 \livelink{chap:DWATdatabitoffset}{DW\_AT\_data\_bit\_offset} &0x6b&\livelink{chap:classconstant}{constant}
1208 \addtoindexx{data bit offset attribute!encoding} \\
1209 \livelink{chap:DWATconstexpr}{DW\_AT\_const\_expr} &0x6c&\livelink{chap:classflag}{flag}
1210 \addtoindexx{constant expression attribute!encoding} \\
1211 \livelink{chap:DWATenumclass}{DW\_AT\_enum\_class} &0x6d&\livelink{chap:classflag}{flag}
1212 \addtoindexx{enumeration class attribute!encoding} \\
1213 \livelink{chap:DWATlinkagename}{DW\_AT\_linkage\_name} &0x6e&\livelink{chap:classstring}{string}
1214 \addtoindexx{linkage name attribute!encoding} \\
1215 \livelink{chap:DWATstringlengthbitsize}{DW\_AT\_string\_length\_bit\_size} \ddag&0x6f&
1216 \livelink{chap:classconstant}{constant}\addtoindexx{string length attribute!size of length} \\
1217 \livelink{chap:DWATstringlengthbytesize}{DW\_AT\_string\_length\_byte\_size} \ddag&0x70&
1218 \livelink{chap:classconstant}{constant}\addtoindexx{string length attribute!size of length} \\
1219 \DWATrankLL \ddag&0x71&
1220 \livelink{chap:DWATrank}{constant, exprloc}\addtoindexx{rank attribute!encoding} \\
1221 \livelink{chap:DWXXXlohiuser}{DW\_AT\_lo\_user}&0x2000 & --- \addtoindexx{low user attribute encoding} \\
1222 \livelink{chap:DWXXXlohiuser}{DW\_AT\_hi\_user}&\xiiifff& --- \addtoindexx{high user attribute encoding} \\
1229 \setlength{\extrarowheight}{0.1cm}
1230 \begin{longtable}{l|l|l}
1231 \caption{Attribute form encodings} \label{tab:attributeformencodings} \\
1232 \hline \bfseries Form name&\bfseries Value &\bfseries Classes \\ \hline
1234 \bfseries Form name&\bfseries Value &\bfseries Classes\\ \hline
1236 \hline \emph{Continued on next page}
1241 \livelink{chap:DWFORMaddr}{DW\_FORM\_addr}&0x01&\livelink{chap:classaddress}{address} \\
1242 \livelink{chap:DWFORMblock2}{DW\_FORM\_block2}&0x03&\livelink{chap:classblock}{block} \\
1243 \livelink{chap:DWFORMblock4}{DW\_FORM\_block4}&0x04&\livelink{chap:classblock}{block} \\
1244 \livelink{chap:DWFORMdata2}{DW\_FORM\_data2}&0x05&\livelink{chap:classconstant}{constant} \\
1245 \livelink{chap:DWFORMdata4}{DW\_FORM\_data4}&0x06&\livelink{chap:classconstant}{constant} \\
1246 \livelink{chap:DWFORMdata8}{DW\_FORM\_data8}&0x07&\livelink{chap:classconstant}{constant} \\
1247 \livelink{chap:DWFORMstring}{DW\_FORM\_string}&0x08&\livelink{chap:classstring}{string} \\
1248 \livelink{chap:DWFORMblock}{DW\_FORM\_block}&0x09&\livelink{chap:classblock}{block} \\
1249 \livelink{chap:DWFORMblock1}{DW\_FORM\_block1}&0x0a&\livelink{chap:classblock}{block} \\
1250 \livelink{chap:DWFORMdata1}{DW\_FORM\_data1}&0x0b&\livelink{chap:classconstant}{constant} \\
1251 \livelink{chap:DWFORMflag}{DW\_FORM\_flag}&0x0c&\livelink{chap:classflag}{flag} \\
1252 \livelink{chap:DWFORMsdata}{DW\_FORM\_sdata}&0x0d&\livelink{chap:classconstant}{constant} \\
1253 \livelink{chap:DWFORMstrp}{DW\_FORM\_strp}&0x0e&\livelink{chap:classstring}{string} \\
1254 \livelink{chap:DWFORMudata}{DW\_FORM\_udata}&0x0f&\livelink{chap:classconstant}{constant} \\
1255 \livelink{chap:DWFORMrefaddr}{DW\_FORM\_ref\_addr}&0x10&\livelink{chap:classreference}{reference} \\
1256 \livelink{chap:DWFORMref1}{DW\_FORM\_ref1}&0x11&\livelink{chap:classreference}{reference} \\
1257 \livelink{chap:DWFORMref2}{DW\_FORM\_ref2}&0x12&\livelink{chap:classreference}{reference} \\
1258 \livelink{chap:DWFORMref4}{DW\_FORM\_ref4}&0x13&\livelink{chap:classreference}{reference} \\
1259 \livelink{chap:DWFORMref8}{DW\_FORM\_ref8}&0x14&\livelink{chap:classreference}{reference} \\
1260 \livelink{chap:DWFORMrefudata}{DW\_FORM\_ref\_udata}&0x15&\livelink{chap:classreference}{reference} \\
1261 \livelink{chap:DWFORMindirect}{DW\_FORM\_indirect}&0x16&(see Section \refersec{datarep:abbreviationstables}) \\
1262 \livelink{chap:DWFORMsecoffset}{DW\_FORM\_sec\_offset} &0x17&\livelink{chap:classlineptr}{lineptr}, \livelink{chap:classloclistptr}{loclistptr}, \livelink{chap:classmacptr}{macptr}, \livelink{chap:classrangelistptr}{rangelistptr} \\
1263 \livelink{chap:DWFORMexprloc}{DW\_FORM\_exprloc} &0x18&\livelink{chap:classexprloc}{exprloc} \\
1264 \livelink{chap:DWFORMflagpresent}{DW\_FORM\_flag\_present} &0x19&\livelink{chap:classflag}{flag} \\
1265 \livelink{chap:DWFORMrefsig8}{DW\_FORM\_ref\_sig8} &0x20&\livelink{chap:classreference}{reference} \\
1272 \section{Variable Length Data}
1273 \label{datarep:variablelengthdata}
1274 \addtoindexx{variable length data|see {LEB128}}
1276 \addtoindexx{Little Endian Base 128|see{LEB128}}
1277 encoded using \doublequote{Little Endian Base 128}
1278 \addtoindexx{little-endian encoding|see{endian attribute}}
1280 \addtoindexx{LEB128}
1281 LEB128 is a scheme for encoding integers
1282 densely that exploits the assumption that most integers are
1285 \textit{This encoding is equally suitable whether the target machine
1286 architecture represents data in big\dash\ endian or little\dash endian
1287 order. It is \doublequote{little\dash endian} only in the sense that it
1288 avoids using space to represent the \doublequote{big} end of an
1289 unsigned integer, when the big end is all zeroes or sign
1292 Unsigned LEB128 (ULEB128) numbers are encoded as follows:
1293 \addtoindexx{LEB128!unsigned, encoding as}
1294 start at the low order end of an unsigned integer and chop
1295 it into 7\dash bit chunks. Place each chunk into the low order 7
1296 bits of a byte. Typically, several of the high order bytes
1297 will be zero; discard them. Emit the remaining bytes in a
1298 stream, starting with the low order byte; set the high order
1299 bit on each byte except the last emitted byte. The high bit
1300 of zero on the last byte indicates to the decoder that it
1301 has encountered the last byte.
1303 The integer zero is a special case, consisting of a single
1306 Table \refersec{tab:examplesofunsignedleb128encodings}
1307 gives some examples of unsigned LEB128 numbers. The
1308 0x80 in each case is the high order bit of the byte, indicating
1309 that an additional byte follows.
1312 The encoding for signed, two\textquoteright s complement LEB128 (SLEB128)
1313 \addtoindexx{LEB128!signed, encoding as}
1314 numbers is similar, except that the criterion for discarding
1315 high order bytes is not whether they are zero, but whether
1316 they consist entirely of sign extension bits. Consider the
1317 32\dash bit integer -2. The three high level bytes of the number
1318 are sign extension, thus LEB128 would represent it as a single
1319 byte containing the low order 7 bits, with the high order
1320 bit cleared to indicate the end of the byte stream. Note
1321 that there is nothing within the LEB128 representation that
1322 indicates whether an encoded number is signed or unsigned. The
1323 decoder must know what type of number to expect.
1324 Table \refersec{tab:examplesofunsignedleb128encodings}
1325 gives some examples of unsigned LEB128 numbers and
1326 Table \refersec{tab:examplesofsignedleb128encodings}
1327 gives some examples of signed LEB128
1330 \textit{Appendix \refersec{app:variablelengthdataencodingdecodinginformative}
1331 \addtoindexx{LEB128!examples}
1332 gives algorithms for encoding and decoding these forms.}
1336 \setlength{\extrarowheight}{0.1cm}
1337 \begin{longtable}{l|l|l}
1338 \caption{Examples of unsigned LEB128 encodings}
1339 \label{tab:examplesofunsignedleb128encodings}
1340 \addtoindexx{LEB128 encoding!examples} \\
1341 \hline \bfseries Number&\bfseries First byte &\bfseries Second byte \\ \hline
1343 \bfseries Number&\bfseries First Byte &\bfseries Second byte\\ \hline
1345 \hline \emph{Continued on next page}
1351 128& 0 + 0x80 & 1 \\
1352 129& 1 + 0x80 & 1 \\
1353 130& 2 + 0x80 & 1 \\
1354 12857& 57 + 0x80 & 100 \\
1361 \setlength{\extrarowheight}{0.1cm}
1362 \begin{longtable}{l|l|l}
1363 \caption{Examples of signed LEB128 encodings} \label{tab:examplesofsignedleb128encodings} \\
1364 \hline \bfseries Number&\bfseries First byte &\bfseries Second byte \\ \hline
1366 \bfseries Number&\bfseries First Byte &\bfseries Second byte\\ \hline
1368 \hline \emph{Continued on next page}
1374 127& 127 + 0x80 & 0 \\
1375 -127& 1 + 0x80 & 0x7f \\
1376 128& 0 + 0x80 & 1 \\
1377 -128& 0 + 0x80 & 0x7f \\
1378 129& 1 + 0x80 & 1 \\
1379 -129& 0x7f + 0x80 & 0x7e \\
1386 \section{DWARF Expressions and Location Descriptions}
1387 \label{datarep:dwarfexpressionsandlocationdescriptions}
1388 \subsection{DWARF Expressions}
1389 \label{datarep:dwarfexpressions}
1392 \addtoindexx{DWARF Expression!operator encoding}
1393 DWARF expression is stored in a \nolink{block} of contiguous
1394 bytes. The bytes form a sequence of operations. Each operation
1395 is a 1\dash byte code that identifies that operation, followed by
1396 zero or more bytes of additional data. The encodings for the
1397 operations are described in
1398 Table \refersec{tab:dwarfoperationencodings}.
1401 \setlength{\extrarowheight}{0.1cm}
1402 \begin{longtable}{l|l|c|l}
1403 \caption{DWARF operation encodings} \label{tab:dwarfoperationencodings} \\
1404 \hline & &\bfseries No. of &\\
1405 \bfseries Operation&\bfseries Code &\bfseries Operands &\bfseries Notes\\ \hline
1407 & &\bfseries No. of &\\
1408 \bfseries Operation&\bfseries Code &\bfseries Operands &\bfseries Notes\\ \hline
1410 \hline \emph{Continued on next page}
1415 \livelink{chap:DWOPaddr}{DW\_OP\_addr}&0x03&1 & constant address \\
1416 & & &(size target specific) \\
1418 \livelink{chap:DWOPderef}{DW\_OP\_deref}&0x06&0 & \\
1421 \livelink{chap:DWOPconst1u}{DW\_OP\_const1u}&0x08&1&1\dash byte constant \\
1422 \livelink{chap:DWOPconst1s}{DW\_OP\_const1s}&0x09&1&1\dash byte constant \\
1423 \livelink{chap:DWOPconst2u}{DW\_OP\_const2u}&0x0a&1&2\dash byte constant \\
1424 \livelink{chap:DWOPconst2s}{DW\_OP\_const2s}&0x0b&1&2\dash byte constant \\
1425 \livelink{chap:DWOPconst4u}{DW\_OP\_const4u}&0x0c&1&4\dash byte constant \\
1426 \livelink{chap:DWOPconst4s}{DW\_OP\_const4s}&0x0d&1&4\dash byte constant \\
1427 \livelink{chap:DWOPconst8u}{DW\_OP\_const8u}&0x0e&1&8\dash byte constant \\
1428 \livelink{chap:DWOPconst8s}{DW\_OP\_const8s}&0x0f&1&8\dash byte constant \\
1429 \livelink{chap:DWOPconstu}{DW\_OP\_constu}&0x10&1&ULEB128 constant \\
1430 \livelink{chap:DWOPconsts}{DW\_OP\_consts}&0x11&1&SLEB128 constant \\
1431 \livelink{chap:DWOPdup}{DW\_OP\_dup}&0x12&0 & \\
1432 \livelink{chap:DWOPdrop}{DW\_OP\_drop}&0x13&0 & \\
1433 \livelink{chap:DWOPover}{DW\_OP\_over}&0x14&0 & \\
1434 \livelink{chap:DWOPpick}{DW\_OP\_pick}&0x15&1&1\dash byte stack index \\
1435 \livelink{chap:DWOPswap}{DW\_OP\_swap}&0x16&0 & \\
1436 \livelink{chap:DWOProt}{DW\_OP\_rot}&0x17&0 & \\
1437 \livelink{chap:DWOPxderef}{DW\_OP\_xderef}&0x18&0 & \\
1438 \livelink{chap:DWOPabs}{DW\_OP\_abs}&0x19&0 & \\
1439 \livelink{chap:DWOPand}{DW\_OP\_and}&0x1a&0 & \\
1440 \livelink{chap:DWOPdiv}{DW\_OP\_div}&0x1b&0 & \\
1444 \livelink{chap:DWOPminus}{DW\_OP\_minus}&0x1c&0 & \\
1445 \livelink{chap:DWOPmod}{DW\_OP\_mod}&0x1d&0 & \\
1446 \livelink{chap:DWOPmul}{DW\_OP\_mul}&0x1e&0 & \\
1447 \livelink{chap:DWOPneg}{DW\_OP\_neg}&0x1f&0 & \\
1448 \livelink{chap:DWOPnot}{DW\_OP\_not}&0x20&0 & \\
1449 \livelink{chap:DWOPor}{DW\_OP\_or}&0x21&0 & \\
1450 \livelink{chap:DWOPplus}{DW\_OP\_plus}&0x22&0 & \\
1451 \livelink{chap:DWOPplusuconst}{DW\_OP\_plus\_uconst}&0x23&1&ULEB128 addend \\
1452 \livelink{chap:DWOPshl}{DW\_OP\_shl}&0x24&0 & \\
1453 \livelink{chap:DWOPshr}{DW\_OP\_shr}&0x25&0 & \\
1454 \livelink{chap:DWOPshra}{DW\_OP\_shra}&0x26&0 & \\
1455 \livelink{chap:DWOPxor}{DW\_OP\_xor}&0x27&0 & \\
1457 \livelink{chap:DWOPbra}{DW\_OP\_bra}&0x28&1 & signed 2\dash byte constant \\
1458 \livelink{chap:DWOPeq}{DW\_OP\_eq}&0x29&0 & \\
1459 \livelink{chap:DWOPge}{DW\_OP\_ge}&0x2a&0 & \\
1460 \livelink{chap:DWOPgt}{DW\_OP\_gt}&0x2b&0 & \\
1461 \livelink{chap:DWOPle}{DW\_OP\_le}&0x2c&0 & \\
1462 \livelink{chap:DWOPlt}{DW\_OP\_lt}&0x2d&0 & \\
1463 \livelink{chap:DWOPne}{DW\_OP\_ne}&0x2e&0 & \\
1464 \livelink{chap:DWOPskip}{DW\_OP\_skip}&0x2f&1&signed 2\dash byte constant \\ \hline
1466 \livelink{chap:DWOPlit0}{DW\_OP\_lit0}&0x30 & 0 & \\
1467 \livelink{chap:DWOPlit1}{DW\_OP\_lit1}&0x31 & 0& literals 0 .. 31 = \\
1468 \ldots & & &\hspace{0.5cm}(\livelink{chap:DWOPlit0}{DW\_OP\_lit0} + literal) \\
1469 \livelink{chap:DWOPlit31}{DW\_OP\_lit31}&0x4f & 0 & \\ \hline
1471 \livelink{chap:DWOPreg0}{DW\_OP\_reg0} & 0x50 & 0 & \\
1472 \livelink{chap:DWOPreg1}{DW\_OP\_reg1} & 0x51 & 0® 0 .. 31 = \\
1473 \ldots & & &\hspace{0.5cm}(\livelink{chap:DWOPreg0}{DW\_OP\_reg0} + regnum) \\
1474 \livelink{chap:DWOPreg31}{DW\_OP\_reg31} & 0x6f & 0 & \\ \hline
1476 \livelink{chap:DWOPbreg0}{DW\_OP\_breg0} & 0x70 &1 & SLEB128 offset \\
1477 \livelink{chap:DWOPbreg1}{DW\_OP\_breg1} & 0x71 & 1 &base register 0 .. 31 = \\
1478 ... & & &\hspace{0.5cm}(\livelink{chap:DWOPbreg0}{DW\_OP\_breg0} + regnum) \\
1479 \livelink{chap:DWOPbreg31}{DW\_OP\_breg31} & 0x8f & 1 & \\ \hline
1481 \livelink{chap:DWOPregx}{DW\_OP\_regx} & 0x90 &1&ULEB128 register \\
1482 \livelink{chap:DWOPfbreg}{DW\_OP\_fbreg} & 0x91&1&SLEB128 offset \\
1483 \livelink{chap:DWOPbregx}{DW\_OP\_bregx} & 0x92&2 &ULEB128 register followed \\
1484 & & & by SLEB128 offset \\
1485 \livelink{chap:DWOPpiece}{DW\_OP\_piece} & 0x93 &1& ULEB128 size of piece addressed \\
1486 \livelink{chap:DWOPderefsize}{DW\_OP\_deref\_size} & 0x94 &1& 1-byte size of data retrieved \\
1487 \livelink{chap:DWOPxderefsize}{DW\_OP\_xderef\_size} & 0x95&1&1-byte size of data retrieved \\
1488 \livelink{chap:DWOPnop}{DW\_OP\_nop} & 0x96 &0& \\
1491 \livelink{chap:DWOPpushobjectaddress}{DW\_OP\_push\_object\_address}&0x97&0 & \\
1492 \livelink{chap:DWOPcall2}{DW\_OP\_call2}&0x98&1& 2\dash byte offset of DIE \\
1493 \livelink{chap:DWOPcall4}{DW\_OP\_call4}&0x99&1& 4\dash byte offset of DIE \\
1494 \livelink{chap:DWOPcallref}{DW\_OP\_call\_ref}&0x9a&1& 4\dash\ or 8\dash byte\\
1495 &&& offset of DIE \\
1496 \livelink{chap:DWOPformtlsaddress}{DW\_OP\_form\_tls\_address}&0x9b &0& \\
1497 \livelink{chap:DWOPcallframecfa}{DW\_OP\_call\_frame\_cfa} &0x9c &0& \\
1498 \livelink{chap:DWOPbitpiece}{DW\_OP\_bit\_piece}&0x9d &2&ULEB128 size followed by \\
1500 \livelink{chap:DWOPimplicitvalue}{DW\_OP\_implicit\_value} &0x9e &2&ULEB128 size followed by \\
1501 &&&\nolink{block} of that size\\
1502 \livelink{chap:DWOPstackvalue}{DW\_OP\_stack\_value} &0x9f &0& \\
1503 \livelink{chap:DWXXXlohiuser}{DW\_OP\_lo\_user} &0xe0 && \\
1504 \livelink{chap:DWXXXlohiuser}{DW\_OP\_hi\_user} &\xff && \\
1510 \subsection{Location Descriptions}
1511 \label{datarep:locationdescriptions}
1513 A location description is used to compute the
1514 location of a variable or other entity.
1516 \subsection{Location Lists}
1517 \label{datarep:locationlists}
1519 Each entry in a \addtoindex{location list} is either a location list entry,
1520 a base address selection entry, or an
1521 \addtoindexx{end of list entry!in location list}
1524 A \addtoindex{location list} entry consists of two address offsets followed
1525 by a 2\dash byte length, followed by a block of contiguous bytes
1526 that contains a DWARF location description. The length
1527 specifies the number of bytes in that block. The two offsets
1528 are the same size as an address on the target machine.
1531 A base address selection entry and an
1532 \addtoindexx{end of list entry!in location list}
1533 end of list entry each
1534 consist of two (constant or relocated) address offsets. The two
1535 offsets are the same size as an address on the target machine.
1537 For a \addtoindex{location list} to be specified, the base address of
1538 \addtoindexx{base address selection entry!in location list}
1539 the corresponding compilation unit must be defined
1540 (see Section \refersec{chap:normalandpartialcompilationunitentries}).
1542 \section{Base Type Attribute Encodings}
1543 \label{datarep:basetypeattributeencodings}
1545 The encodings of the
1546 \hypertarget{chap:DWATencodingencodingofbasetype}
1548 \addtoindexx{encoding attribute!encoding}
1550 \livelink{chap:DWATencoding}{DW\_AT\_encoding}
1551 attribute are given in
1552 Table \refersec{tab:basetypeencodingvalues}
1555 \setlength{\extrarowheight}{0.1cm}
1556 \begin{longtable}{l|c}
1557 \caption{Base type encoding values} \label{tab:basetypeencodingvalues} \\
1558 \hline \bfseries Base type encoding code name&\bfseries Value \\ \hline
1560 \bfseries Base type encoding code name&\bfseries Value\\ \hline
1562 \hline \emph{Continued on next page}
1566 \livelink{chap:DWATEaddress}{DW\_ATE\_address}&0x01 \\
1567 \livelink{chap:DWATEboolean}{DW\_ATE\_boolean}&0x02 \\
1568 \livelink{chap:DWATEcomplexfloat}{DW\_ATE\_complex\_float}&0x03 \\
1569 \livelink{chap:DWATEfloat}{DW\_ATE\_float}&0x04 \\
1570 \livelink{chap:DWATEsigned}{DW\_ATE\_signed}&0x05 \\
1571 \livelink{chap:DWATEsignedchar}{DW\_ATE\_signed\_char}&0x06 \\
1572 \livelink{chap:DWATEunsigned}{DW\_ATE\_unsigned}&0x07 \\
1573 \livelink{chap:DWATEunsignedchar}{DW\_ATE\_unsigned\_char}&0x08 \\
1574 \livelink{chap:DWATEimaginaryfloat}{DW\_ATE\_imaginary\_float}&0x09 \\
1575 \livelink{chap:DWATEpackeddecimal}{DW\_ATE\_packed\_decimal}&0x0a \\
1576 \livelink{chap:DWATEnumericstring}{DW\_ATE\_numeric\_string}&0x0b \\
1577 \livelink{chap:DWATEedited}{DW\_ATE\_edited}&0x0c \\
1578 \livelink{chap:DWATEsignedfixed}{DW\_ATE\_signed\_fixed}&0x0d \\
1579 \livelink{chap:DWATEunsignedfixed}{DW\_ATE\_unsigned\_fixed}&0x0e \\
1580 \livelink{chap:DWATEdecimalfloat}{DW\_ATE\_decimal\_float} & 0x0f \\
1581 \livelink{chap:DWATEUTF}{DW\_ATE\_UTF} & 0x10 \\
1582 \livelink{chap:DWXXXlohiuser}{DW\_ATE\_lo\_user} & 0x80 \\
1583 \livelink{chap:DWXXXlohiuser}{DW\_ATE\_hi\_user} & \xff \\
1588 The encodings of the constants used in the
1589 \livelink{chap:DWATdecimalsign}{DW\_AT\_decimal\_sign} attribute
1591 Table \refersec{tab:decimalsignencodings}.
1594 \setlength{\extrarowheight}{0.1cm}
1595 \begin{longtable}{l|c}
1596 \caption{Decimal sign encodings} \label{tab:decimalsignencodings} \\
1597 \hline \bfseries Decimal sign code name&\bfseries Value \\ \hline
1599 \bfseries Decimal sign code name&\bfseries Value\\ \hline
1601 \hline \emph{Continued on next page}
1606 \livelink{chap:DWDSunsigned}{DW\_DS\_unsigned} & 0x01 \\
1607 \livelink{chap:DWDSleadingoverpunch}{DW\_DS\_leading\_overpunch} & 0x02 \\
1608 \livelink{chap:DWDStrailingoverpunch}{DW\_DS\_trailing\_overpunch} & 0x03 \\
1609 \livelink{chap:DWDSleadingseparate}{DW\_DS\_leading\_separate} & 0x04 \\
1610 \livelink{chap:DWDStrailingseparate}{DW\_DS\_trailing\_separate} & 0x05 \\
1615 The encodings of the constants used in the
1616 \livelink{chap:DWATendianity}{DW\_AT\_endianity} attribute are given in
1617 Table \refersec{tab:endianityencodings}.
1620 \setlength{\extrarowheight}{0.1cm}
1621 \begin{longtable}{l|c}
1622 \caption{Endianity encodings} \label{tab:endianityencodings}\\
1623 \hline \bfseries Endian code name&\bfseries Value \\ \hline
1625 \bfseries Endian code name&\bfseries Value\\ \hline
1627 \hline \emph{Continued on next page}
1632 \livelink{chap:DWENDdefault}{DW\_END\_default} & 0x00 \\
1633 \livelink{chap:DWENDbig}{DW\_END\_big} & 0x01 \\
1634 \livelink{chap:DWENDlittle}{DW\_END\_little} & 0x02 \\
1635 \livelink{chap:DWXXXlohiuser}{DW\_END\_lo\_user} & 0x40 \\
1636 \livelink{chap:DWXXXlohiuser}{DW\_END\_hi\_user} & \xff \\
1641 \section{Accessibility Codes}
1642 \label{datarep:accessibilitycodes}
1643 The encodings of the constants used in the
1644 \livelink{chap:DWATaccessibility}{DW\_AT\_accessibility}
1646 \addtoindexx{accessibility attribute!encoding}
1648 Table \refersec{tab:accessibilityencodings}.
1651 \setlength{\extrarowheight}{0.1cm}
1652 \begin{longtable}{l|c}
1653 \caption{Accessibility encodings} \label{tab:accessibilityencodings}\\
1654 \hline \bfseries Accessibility code name&\bfseries Value \\ \hline
1656 \bfseries Accessibility code name&\bfseries Value\\ \hline
1658 \hline \emph{Continued on next page}
1663 \livelink{chap:DWACCESSpublic}{DW\_ACCESS\_public}&0x01 \\
1664 \livelink{chap:DWACCESSprotected}{DW\_ACCESS\_protected}&0x02 \\
1665 \livelink{chap:DWACCESSprivate}{DW\_ACCESS\_private}&0x03 \\
1671 \section{Visibility Codes}
1672 \label{datarep:visibilitycodes}
1673 The encodings of the constants used in the
1674 \livelink{chap:DWATvisibility}{DW\_AT\_visibility} attribute are given in
1675 Table \refersec{tab:visibilityencodings}.
1678 \setlength{\extrarowheight}{0.1cm}
1679 \begin{longtable}{l|c}
1680 \caption{Visibility encodings} \label{tab:visibilityencodings}\\
1681 \hline \bfseries Visiibility code name&\bfseries Value \\ \hline
1683 \bfseries Visibility code name&\bfseries Value\\ \hline
1685 \hline \emph{Continued on next page}
1690 \livelink{chap:DWVISlocal}{DW\_VIS\_local}&0x01 \\
1691 \livelink{chap:DWVISexported}{DW\_VIS\_exported}&0x02 \\
1692 \livelink{chap:DWVISqualified}{DW\_VIS\_qualified}&0x03 \\
1697 \section{Virtuality Codes}
1698 \label{datarep:vitualitycodes}
1700 The encodings of the constants used in the
1701 \livelink{chap:DWATvirtuality}{DW\_AT\_virtuality} attribute are given in
1702 Table \refersec{tab:virtualityencodings}.
1705 \setlength{\extrarowheight}{0.1cm}
1706 \begin{longtable}{l|c}
1707 \caption{Virtuality encodings} \label{tab:virtualityencodings}\\
1708 \hline \bfseries Virtuality code name&\bfseries Value \\ \hline
1710 \bfseries Virtuality code name&\bfseries Value\\ \hline
1712 \hline \emph{Continued on next page}
1717 \livelink{chap:DWVIRTUALITYnone}{DW\_VIRTUALITY\_none}&0x00 \\
1718 \livelink{chap:DWVIRTUALITYvirtual}{DW\_VIRTUALITY\_virtual}&0x01 \\
1719 \livelink{chap:DWVIRTUALITYpurevirtual}{DW\_VIRTUALITY\_pure\_virtual}&0x02 \\
1727 \livelink{chap:DWVIRTUALITYnone}{DW\_VIRTUALITY\_none} is equivalent to the absence of the
1728 \livelink{chap:DWATvirtuality}{DW\_AT\_virtuality}
1731 \section{Source Languages}
1732 \label{datarep:sourcelanguages}
1734 The encodings of the constants used
1735 \addtoindexx{language attribute, encoding}
1737 \addtoindexx{language name encoding}
1739 \livelink{chap:DWATlanguage}{DW\_AT\_language}
1740 attribute are given in
1741 Table \refersec{tab:languageencodings}.
1743 % If we don't force a following space it looks odd
1745 and their associated values are reserved, but the
1746 languages they represent are not well supported.
1747 Table \refersec{tab:languageencodings}
1749 \addtoindexx{lower bound attribute!default}
1750 default lower bound, if any, assumed for
1751 an omitted \livelink{chap:DWATlowerbound}{DW\_AT\_lower\_bound} attribute in the context of a
1752 \livelink{chap:DWTAGsubrangetype}{DW\_TAG\_subrange\_type} debugging information entry for each
1756 \setlength{\extrarowheight}{0.1cm}
1757 \begin{longtable}{l|c|c}
1758 \caption{Language encodings} \label{tab:languageencodings}\\
1759 \hline \bfseries Language name&\bfseries Value &\bfseries Default Lower Bound \\ \hline
1761 \bfseries Language name&\bfseries Value &\bfseries Default Lower Bound\\ \hline
1763 \hline \emph{Continued on next page}
1766 \dag \ \textit{See text} \\ \ddag \ \textit{New in \addtoindex{DWARF Version 5}}
1769 \livelink{chap:DWLANGC89}{DW\_LANG\_C89} &0x0001 &0 \\
1770 \livelink{chap:DWLANGC}{DW\_LANG\_C} &0x0002 &0 \\
1771 \livelink{chap:DWLANGAda83}{DW\_LANG\_Ada83} \dag &0x0003 &1 \addtoindexx{Ada} \\
1772 \livelink{chap:DWLANGCplusplus}{DW\_LANG\_C\_plus\_plus} &0x0004 &0 \\
1773 \livelink{chap:DWLANGCobol74}{DW\_LANG\_Cobol74} \dag &0x0005 &1 \\
1774 \livelink{chap:DWLANGCobol85}{DW\_LANG\_Cobol85} \dag &0x0006 &1 \\
1775 \livelink{chap:DWLANGFortran77}{DW\_LANG\_Fortran77} &0x0007 &1 \\
1776 \livelink{chap:DWLANGFortran90}{DW\_LANG\_Fortran90} &0x0008 &1 \\
1777 \livelink{chap:DWLANGPascal83}{DW\_LANG\_Pascal83} &0x0009 &1 \\
1778 \livelink{chap:DWLANGModula2}{DW\_LANG\_Modula2} &0x000a &1 \\
1779 \livelink{chap:DWLANGJava}{DW\_LANG\_Java}&0x000b &0 \\
1780 \livelink{chap:DWLANGC99}{DW\_LANG\_C99}&0x000c &0 \\
1781 \livelink{chap:DWLANGAda95}{DW\_LANG\_Ada95} \dag &0x000d &1 \addtoindexx{Ada} \\
1782 \livelink{chap:DWLANGFortran95}{DW\_LANG\_Fortran95} &0x000e &1 \\
1783 \livelink{chap:DWLANGPLI}{DW\_LANG\_PLI} \dag &0x000f &1 \\
1784 \livelink{chap:DWLANGObjC}{DW\_LANG\_ObjC} &0x0010 &0 \\
1785 \livelink{chap:DWLANGObjCplusplus}{DW\_LANG\_ObjC\_plus\_plus} &0x0011 &0 \\
1786 \livelink{chap:DWLANGUPC}{DW\_LANG\_UPC} &0x0012 &0 \\
1787 \livelink{chap:DWLANGD}{DW\_LANG\_D} &0x0013 &0 \\
1788 \livelink{chap:DWLANGPython}{DW\_LANG\_Python} \dag &0x0014 &0 \\
1789 \livelink{chap:DWLANGOpenCL}{DW\_LANG\_OpenCL} \dag \ddag &0x0015 &0 \\
1790 \livelink{chap:DWLANGGo}{DW\_LANG\_Go} \dag \ddag &0x0016 &0 \\
1791 \livelink{chap:DWLANGModula3}{DW\_LANG\_Modula3} \dag \ddag &0x0017 &1 \\
1792 \livelink{chap:DWLANGHaskell}{DW\_LANG\_Haskell} \dag \ddag &0x0018 &0 \\
1793 \livelink{chap:DWXXXlohiuser}{DW\_LANG\_lo\_user} &0x8000 & \\
1794 \livelink{chap:DWXXXlohiuser}{DW\_LANG\_hi\_user} &\xffff & \\
1799 \section{Address Class Encodings}
1800 \label{datarep:addressclassencodings}
1802 The value of the common
1803 \addtoindexi{address}{address class!attribute encoding}
1805 \livelink{chap:DWADDRnone}{DW\_ADDR\_none} is 0.
1808 \section{Identifier Case}
1809 \label{datarep:identifiercase}
1811 The encodings of the constants used in the
1812 \livelink{chap:DWATidentifiercase}{DW\_AT\_identifier\_case} attribute are given in
1813 Table \refersec{tab:identifiercaseencodings}.
1816 \setlength{\extrarowheight}{0.1cm}
1817 \begin{longtable}{l|c}
1818 \caption{Identifier case encodings} \label{tab:identifiercaseencodings}\\
1819 \hline \bfseries Identifier case name&\bfseries Value \\ \hline
1821 \bfseries Identifier case name&\bfseries Value\\ \hline
1823 \hline \emph{Continued on next page}
1827 \livelink{chap:DWIDcasesensitive}{DW\_ID\_case\_sensitive}&0x00 \\
1828 \livelink{chap:DWIDupcase}{DW\_ID\_up\_case}&0x01 \\
1829 \livelink{chap:DWIDdowncase}{DW\_ID\_down\_case}&0x02 \\
1830 \livelink{chap:DWIDcaseinsensitive}{DW\_ID\_case\_insensitive}&0x03 \\
1834 \section{Calling Convention Encodings}
1835 \label{datarep:callingconventionencodings}
1836 The encodings of the constants used in the
1837 \livelink{chap:DWATcallingconvention}{DW\_AT\_calling\_convention} attribute are given in
1838 Table \refersec{tab:callingconventionencodings}.
1841 \setlength{\extrarowheight}{0.1cm}
1842 \begin{longtable}{l|c}
1843 \caption{Calling convention encodings} \label{tab:callingconventionencodings}\\
1844 \hline \bfseries Calling Convention name&\bfseries Value \\ \hline
1846 \bfseries Calling Convention name&\bfseries Value\\ \hline
1848 \hline \emph{Continued on next page}
1853 \livelink{chap:DWCCnormal}{DW\_CC\_normal}&0x01 \\
1854 \livelink{chap:DWCCprogram}{DW\_CC\_program}&0x02 \\
1855 \livelink{chap:DWCCnocall}{DW\_CC\_nocall}&0x03 \\
1856 \livelink{chap:DWXXXlohiuser}{DW\_CC\_lo\_user}&0x40 \\
1857 \livelink{chap:DWXXXlohiuser}{DW\_CC\_hi\_user}&\xff \\
1862 \section{Inline Codes}
1863 \label{datarep:inlinecodes}
1865 The encodings of the constants used in
1866 \addtoindexx{inline attribute!encoding}
1868 \livelink{chap:DWATinline}{DW\_AT\_inline} attribute are given in
1869 Table \refersec{tab:inlineencodings}.
1873 \setlength{\extrarowheight}{0.1cm}
1874 \begin{longtable}{l|c}
1875 \caption{Inline encodings} \label{tab:inlineencodings}\\
1876 \hline \bfseries Inline Code name&\bfseries Value \\ \hline
1878 \bfseries Inline Code name&\bfseries Value\\ \hline
1880 \hline \emph{Continued on next page}
1885 \livelink{chap:DWINLnotinlined}{DW\_INL\_not\_inlined}&0x00 \\
1886 \livelink{chap:DWINLinlined}{DW\_INL\_inlined}&0x01 \\
1887 \livelink{chap:DWINLdeclarednotinlined}{DW\_INL\_declared\_not\_inlined}&0x02 \\
1888 \livelink{chap:DWINLdeclaredinlined}{DW\_INL\_declared\_inlined}&0x03 \\
1893 % this clearpage is ugly, but the following table came
1894 % out oddly without it.
1896 \section{Array Ordering}
1897 \label{datarep:arrayordering}
1899 The encodings of the constants used in the
1900 \livelink{chap:DWATordering}{DW\_AT\_ordering} attribute are given in
1901 Table \refersec{tab:orderingencodings}.
1905 \setlength{\extrarowheight}{0.1cm}
1906 \begin{longtable}{l|c}
1907 \caption{Ordering encodings} \label{tab:orderingencodings}\\
1908 \hline \bfseries Ordering name&\bfseries Value \\ \hline
1910 \bfseries Ordering name&\bfseries Value\\ \hline
1912 \hline \emph{Continued on next page}
1917 \livelink{chap:DWORDrowmajor}{DW\_ORD\_row\_major}&0x00 \\
1918 \livelink{chap:DWORDcolmajor}{DW\_ORD\_col\_major}&0x01 \\
1924 \section{Discriminant Lists}
1925 \label{datarep:discriminantlists}
1927 The descriptors used in
1928 \addtoindexx{discriminant list attribute!encoding}
1930 \livelink{chap:DWATdiscrlist}{DW\_AT\_discr\_list} attribute are
1931 encoded as 1\dash byte constants. The
1932 defined values are given in
1933 Table \refersec{tab:discriminantdescriptorencodings}.
1935 % Odd that the 'Name' field capitalized here, it is not caps elsewhere.
1937 \setlength{\extrarowheight}{0.1cm}
1938 \begin{longtable}{l|c}
1939 \caption{Discriminant descriptor encodings} \label{tab:discriminantdescriptorencodings}\\
1940 \hline \bfseries Descriptor Name&\bfseries Value \\ \hline
1942 \bfseries Descriptor Name&\bfseries Value\\ \hline
1944 \hline \emph{Continued on next page}
1949 \livelink{chap:DWDSClabel}{DW\_DSC\_label}&0x00 \\
1950 \livelink{chap:DWDSCrange}{DW\_DSC\_range}&0x01 \\
1956 \section{Name Lookup Tables}
1957 \label{datarep:namelookuptables}
1959 Each set of entries in the table of global names contained
1960 in the \dotdebugpubnames{} and
1961 \dotdebugpubtypes{} sections begins
1962 with a header consisting of:
1963 \begin{enumerate}[1. ]
1965 \item \texttt{unit\_length} (\livelink{datarep:initiallengthvalues}{initial length}) \\
1966 \addttindexx{unit\_length}
1967 A 4\dash byte or 12\dash byte unsigned integer
1968 \addtoindexx{initial length}
1969 representing the length
1970 of the \dotdebuginfo{}
1971 contribution for that compilation unit,
1972 not including the length field itself. In the
1973 \thirtytwobitdwarfformat, this is a 4\dash byte unsigned integer (which must be less
1974 than \xfffffffzero); in the \sixtyfourbitdwarfformat, this consists
1975 of the 4\dash byte value \wffffffff followed by an 8\dash byte unsigned
1976 integer that gives the actual length
1977 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
1979 \item version (\addtoindex{uhalf}) \\
1980 A 2\dash byte unsigned integer representing the version of the
1981 DWARF information for the name lookup table
1982 \addtoindexx{version number!name lookup table}
1983 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
1984 The value in this field is 2.
1987 \item \addtoindex{debug\_info\_offset} (section offset) \\
1989 \addtoindexx{section offset!in name lookup table set of entries}
1990 4\dash byte or 8\dash byte
1993 section of the compilation unit header.
1994 In the \thirtytwobitdwarfformat, this is a 4\dash byte unsigned offset;
1995 in the \sixtyfourbitdwarfformat, this is an 8\dash byte unsigned offsets
1996 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
1998 \item \addtoindex{debug\_info\_length} (\livelink{datarep:sectionoffsetlength}{section length}) \\
1999 \addtoindexx{section length!in .debug\_pubnames header}
2001 \addtoindexx{section length!in .debug\_pubtypes header}
2002 4\dash byte or 8\dash byte length containing the size in bytes of the
2003 contents of the \dotdebuginfo{}
2004 section generated to represent
2005 this compilation unit. In the \thirtytwobitdwarfformat, this is
2006 a 4\dash byte unsigned length; in the \sixtyfourbitdwarfformat, this
2007 is an 8-byte unsigned length
2008 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
2013 This header is followed by a series of tuples. Each tuple
2014 consists of a 4\dash byte or 8\dash byte offset followed by a string
2015 of non\dash null bytes terminated by one null byte.
2017 DWARF format, this is a 4\dash byte offset; in the 64\dash bit DWARF
2018 format, it is an 8\dash byte offset.
2019 Each set is terminated by an
2020 offset containing the value 0.
2024 \section{Address Range Table}
2025 \label{datarep:addrssrangetable}
2027 Each set of entries in the table of address ranges contained
2028 in the \dotdebugaranges{}
2029 section begins with a header containing:
2030 \begin{enumerate}[1. ]
2031 % FIXME The unit length text is not fully consistent across
2034 \item \texttt{unit\_length} (\livelink{datarep:initiallengthvalues}{initial length}) \\
2035 \addttindexx{unit\_length}
2036 A 4-byte or 12-byte length containing the length of the
2037 \addtoindexx{initial length}
2038 set of entries for this compilation unit, not including the
2039 length field itself. In the \thirtytwobitdwarfformat, this is a
2040 4-byte unsigned integer (which must be less than \xfffffffzero);
2041 in the \sixtyfourbitdwarfformat, this consists of the 4-byte value
2042 \wffffffff followed by an 8-byte unsigned integer that gives
2044 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
2046 \item version (\addtoindex{uhalf}) \\
2047 A 2\dash byte version identifier representing the version of the
2048 DWARF information for the address range table
2049 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
2050 This value in this field \addtoindexx{version number!address range table} is 2.
2053 \item debug\_info\_offset (\livelink{datarep:sectionoffsetlength}{section offset}) \\
2055 \addtoindexx{section offset!in .debug\_aranges header}
2056 4\dash byte or 8\dash byte offset into the
2057 \dotdebuginfo{} section of
2058 the compilation unit header. In the \thirtytwobitdwarfformat,
2059 this is a 4\dash byte unsigned offset; in the \sixtyfourbitdwarfformat,
2060 this is an 8\dash byte unsigned offset
2061 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
2063 \item address\_size (ubyte) \\
2064 A 1\dash byte unsigned integer containing the size in bytes of an
2065 \addtoindexx{address\_size}
2067 \addtoindexx{size of an address}
2068 (or the offset portion of an address for segmented
2069 \addtoindexx{address space!segmented}
2070 addressing) on the target system.
2072 \item segment\_size (ubyte) \\
2074 \addtoindexx{segment\_size}
2075 1\dash byte unsigned integer containing the size in bytes of a
2076 segment selector on the target system.
2080 This header is followed by a series of tuples. Each tuple
2081 consists of a segment, an address and a length.
2083 size is given by the \addtoindex{segment\_size} field of the header; the
2084 address and length size are each given by the address\_size
2085 field of the header.
2086 The first tuple following the header in
2087 each set begins at an offset that is a multiple of the size
2088 of a single tuple (that is, the size of a segment selector
2089 plus twice the \addtoindex{size of an address}).
2090 The header is padded, if
2091 necessary, to that boundary. Each set of tuples is terminated
2092 by a 0 for the segment, a 0 for the address and 0 for the
2093 length. If the \addtoindex{segment\_size} field in the header is zero,
2094 the segment selectors are omitted from all tuples, including
2095 the terminating tuple.
2098 \section{Line Number Information}
2099 \label{datarep:linenumberinformation}
2101 The \addtoindexi{version number}{version number!line number information}
2102 in the line number program header is 4
2103 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
2105 The boolean values \doublequote{true} and \doublequote{false}
2106 used by the line number information program are encoded
2107 as a single byte containing the value 0
2108 for \doublequote{false,} and a non-zero value for \doublequote{true.}
2110 The encodings for the standard opcodes are given in
2111 \addtoindexx{line number opcodes!standard opcode encoding}
2112 Table \refersec{tab:linenumberstandardopcodeencodings}.
2114 % Odd that the 'Name' field capitalized here, it is not caps elsewhere.
2116 \setlength{\extrarowheight}{0.1cm}
2117 \begin{longtable}{l|c}
2118 \caption{Line number standard opcode encodings} \label{tab:linenumberstandardopcodeencodings}\\
2119 \hline \bfseries Opcode name&\bfseries Value \\ \hline
2121 \bfseries Opcode name&\bfseries Value\\ \hline
2123 \hline \emph{Continued on next page}
2128 \livelink{chap:DWLNScopy}{DW\_LNS\_copy}&0x01 \\
2129 \livelink{chap:DWLNSadvancepc}{DW\_LNS\_advance\_pc}&0x02 \\
2130 \livelink{chap:DWLNSadvanceline}{DW\_LNS\_advance\_line}&0x03 \\
2131 \livelink{chap:DWLNSsetfile}{DW\_LNS\_set\_file}&0x04 \\
2132 \livelink{chap:DWLNSsetcolumn}{DW\_LNS\_set\_column}&0x05 \\
2133 \livelink{chap:DWLNSnegatestmt}{DW\_LNS\_negate\_stmt}&0x06 \\
2134 \livelink{chap:DWLNSsetbasicblock}{DW\_LNS\_set\_basic\_block}&0x07 \\
2135 \livelink{chap:DWLNSconstaddpc}{DW\_LNS\_const\_add\_pc}&0x08 \\
2136 \livelink{chap:DWLNSfixedadvancepc}{DW\_LNS\_fixed\_advance\_pc}&0x09 \\
2137 \livelink{chap:DWLNSsetprologueend}{DW\_LNS\_set\_prologue\_end}&0x0a \\
2138 \livelink{chap:DWLNSsetepiloguebegin}{DW\_LNS\_set\_epilogue\_begin}&0x0b \\
2139 \livelink{chap:DWLNSsetisa}{DW\_LNS\_set\_isa}&0x0c \\
2146 The encodings for the extended opcodes are given in
2147 \addtoindexx{line number opcodes!extended opcode encoding}
2148 Table \refersec{tab:linenumberextendedopcodeencodings}.
2151 \setlength{\extrarowheight}{0.1cm}
2152 \begin{longtable}{l|c}
2153 \caption{Line number extended opcode encodings} \label{tab:linenumberextendedopcodeencodings}\\
2154 \hline \bfseries Opcode name&\bfseries Value \\ \hline
2156 \bfseries Opcode name&\bfseries Value\\ \hline
2158 \hline \emph{Continued on next page}
2163 \livelink{chap:DWLNEendsequence}{DW\_LNE\_end\_sequence}&0x01 \\
2164 \livelink{chap:DWLNEsetaddress}{DW\_LNE\_set\_address}&0x02\\
2165 \livelink{chap:DWLNEdefinefile}{DW\_LNE\_define\_file}&0x03\\
2166 \livelink{chap:DWLNEsetdiscriminator}{DW\_LNE\_set\_discriminator} &0x04 \\
2167 \livelink{chap:DWXXXlohiuser}{DW\_LNE\_lo\_user}&0x80 \\
2168 \livelink{chap:DWXXXlohiuser}{DW\_LNE\_hi\_user}&\xff \\
2173 \section{Macro Information}
2174 \label{datarep:macroinformation}
2176 The source line numbers and source file indices encoded in the
2177 macro information section are represented as unsigned LEB128
2178 numbers as are the constants in a
2179 \livelink{chap:DWMACINFOvendorext}{DW\_MACINFO\_vendor\_ext} entry.
2181 The macinfo type is encoded as a single byte.
2183 \addtoindexx{macinfo types!encoding}
2185 Table \refersec{tab:macinfotypeencodings}.
2189 \setlength{\extrarowheight}{0.1cm}
2190 \begin{longtable}{l|c}
2191 \caption{Macinfo type encodings} \label{tab:macinfotypeencodings}\\
2192 \hline \bfseries Macinfo Type Name&\bfseries Value \\ \hline
2194 \bfseries Macinfo Type Name&\bfseries Value\\ \hline
2196 \hline \emph{Continued on next page}
2201 \livelink{chap:DWMACINFOdefine}{DW\_MACINFO\_define}&0x01 \\
2202 \livelink{chap:DWMACINFOundef}{DW\_MACINFO\_undef}&0x02 \\
2203 \livelink{chap:DWMACINFOstartfile}{DW\_MACINFO\_start\_file}&0x03 \\
2204 \livelink{chap:DWMACINFOendfile}{DW\_MACINFO\_end\_file}&0x04 \\
2205 \livelink{chap:DWMACINFOvendorext}{DW\_MACINFO\_vendor\_ext}&\xff \\
2211 \section{Call Frame Information}
2212 \label{datarep:callframeinformation}
2214 In the \thirtytwobitdwarfformat, the value of the CIE id in the
2215 CIE header is \xffffffff; in the \sixtyfourbitdwarfformat, the
2216 value is \xffffffffffffffff.
2218 The value of the CIE \addtoindexi{version number}{version number!call frame information}
2219 is 4 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
2221 Call frame instructions are encoded in one or more bytes. The
2222 primary opcode is encoded in the high order two bits of
2223 the first byte (that is, opcode = byte $\gg$ 6). An operand
2224 or extended opcode may be encoded in the low order 6
2225 bits. Additional operands are encoded in subsequent bytes.
2226 The instructions and their encodings are presented in
2227 Table \refersec{tab:callframeinstructionencodings}.
2230 \setlength{\extrarowheight}{0.1cm}
2231 \begin{longtable}{l|c|c|l|l}
2232 \caption{Call frame instruction encodings} \label{tab:callframeinstructionencodings} \\
2233 \hline &\bfseries High 2 &\bfseries Low 6 & & \\
2234 \bfseries Instruction&\bfseries Bits &\bfseries Bits &\bfseries Operand 1 &\bfseries Operand 2\\ \hline
2236 & \bfseries High 2 &\bfseries Low 6 & &\\
2237 \bfseries Instruction&\bfseries Bits &\bfseries Bits &\bfseries Operand 1 &\bfseries Operand 2\\ \hline
2239 \hline \emph{Continued on next page}
2244 \livelink{chap:DWCFAadvanceloc}{DW\_CFA\_advance\_loc}&0x1&delta & \\
2245 \livelink{chap:DWCFAoffset}{DW\_CFA\_offset}&0x2®ister&ULEB128 offset \\
2246 \livelink{chap:DWCFArestore}{DW\_CFA\_restore}&0x3®ister & & \\
2247 \livelink{chap:DWCFAnop}{DW\_CFA\_nop}&0&0 & & \\
2248 \livelink{chap:DWCFAsetloc}{DW\_CFA\_set\_loc}&0&0x01&address & \\
2249 \livelink{chap:DWCFAadvanceloc1}{DW\_CFA\_advance\_loc1}&0&0x02&1\dash byte delta & \\
2250 \livelink{chap:DWCFAadvanceloc2}{DW\_CFA\_advance\_loc2}&0&0x03&2\dash byte delta & \\
2251 \livelink{chap:DWCFAadvanceloc4}{DW\_CFA\_advance\_loc4}&0&0x04&4\dash byte delta & \\
2252 \livelink{chap:DWCFAoffsetextended}{DW\_CFA\_offset\_extended}&0&0x05&ULEB128 register&ULEB128 offset \\
2253 \livelink{chap:DWCFArestoreextended}{DW\_CFA\_restore\_extended}&0&0x06&ULEB128 register & \\
2254 \livelink{chap:DWCFAundefined}{DW\_CFA\_undefined}&0&0x07&ULEB128 register & \\
2255 \livelink{chap:DWCFAsamevalue}{DW\_CFA\_same\_value}&0&0x08 &ULEB128 register & \\
2256 \livelink{chap:DWCFAregister}{DW\_CFA\_register}&0&0x09&ULEB128 register &ULEB128 offset \\
2257 \livelink{chap:DWCFArememberstate}{DW\_CFA\_remember\_state}&0&0x0a & & \\
2258 \livelink{chap:DWCFArestorestate}{DW\_CFA\_restore\_state}&0&0x0b & & \\
2259 \livelink{chap:DWCFAdefcfa}{DW\_CFA\_def\_cfa}&0&0x0c &ULEB128 register&ULEB128 offset \\
2260 \livelink{chap:DWCFAdefcfaregister}{DW\_CFA\_def\_cfa\_register}&0&0x0d&ULEB128 register & \\
2261 \livelink{chap:DWCFAdefcfaoffset}{DW\_CFA\_def\_cfa\_offset}&0&0x0e &ULEB128 offset & \\
2262 \livelink{chap:DWCFAdefcfaexpression}{DW\_CFA\_def\_cfa\_expression}&0&0x0f &BLOCK \\
2263 \livelink{chap:DWCFAexpression}{DW\_CFA\_expression}&0&0x10&ULEB128 register & BLOCK \\
2265 \livelink{chap:DWCFAoffsetextendedsf}{DW\_CFA\_offset\_extended\_sf}&0&0x11&ULEB128 register&SLEB128 offset \\
2266 \livelink{chap:DWCFAdefcfasf}{DW\_CFA\_def\_cfa\_sf}&0&0x12&ULEB128 register&SLEB128 offset \\
2267 \livelink{chap:DWCFAdefcfaoffsetsf}{DW\_CFA\_def\_cfa\_offset\_sf}&0&0x13&SLEB128 offset & \\
2268 \livelink{chap:DWCFAvaloffset}{DW\_CFA\_val\_offset}&0&0x14&ULEB128&ULEB128 \\
2269 \livelink{chap:DWCFAvaloffsetsf}{DW\_CFA\_val\_offset\_sf}&0&0x15&ULEB128&SLEB128 \\
2270 \livelink{chap:DWCFAvalexpression}{DW\_CFA\_val\_expression}&0&0x16&ULEB128&BLOCK \\
2271 \livelink{chap:DWXXXlohiuser}{DW\_CFA\_lo\_user}&0&0x1c & & \\
2272 \livelink{chap:DWXXXlohiuser}{DW\_CFA\_hi\_user}&0&\xiiif & & \\
2276 \section{Non-contiguous Address Ranges}
2277 \label{datarep:noncontiguousaddressranges}
2279 Each entry in a \addtoindex{range list}
2280 (see Section \refersec{chap:noncontiguousaddressranges})
2282 \addtoindexx{base address selection entry!in range list}
2284 \addtoindexx{range list}
2285 a base address selection entry, or an end
2288 A \addtoindex{range list} entry consists of two relative addresses. The
2289 addresses are the same size as addresses on the target machine.
2291 A base address selection entry and an
2292 \addtoindexx{end of list entry!in range list}
2293 end of list entry each
2294 \addtoindexx{base address selection entry!in range list}
2295 consist of two (constant or relocated) addresses. The two
2296 addresses are the same size as addresses on the target machine.
2298 For a \addtoindex{range list} to be specified, the base address of the
2299 \addtoindexx{base address selection entry!in range list}
2300 corresponding compilation unit must be defined
2301 (see Section \refersec{chap:normalandpartialcompilationunitentries}).
2304 \section{Dependencies and Constraints}
2305 \label{datarep:dependenciesandconstraints}
2307 The debugging information in this format is intended to
2309 \addtoindexx{DWARF section names!list of}
2311 the \dotdebugabbrev{},
2318 \dotdebugpubnames{},
2319 \dotdebugpubtypes{},
2324 sections of an object file, or equivalent
2325 separate file or database. The information is not
2326 word\dash aligned. Consequently:
2329 \item For the \thirtytwobitdwarfformat{} and a target architecture with
2330 32\dash bit addresses, an assembler or compiler must provide a way
2331 to produce 2\dash byte and 4\dash byte quantities without alignment
2332 restrictions, and the linker must be able to relocate a
2333 4\dash byte address or
2334 \addtoindexx{section offset!alignment of}
2335 section offset that occurs at an arbitrary
2338 \item For the \thirtytwobitdwarfformat{} and a target architecture with
2339 64\dash bit addresses, an assembler or compiler must provide a
2340 way to produce 2\dash byte, 4\dash byte and 8\dash byte quantities without
2341 alignment restrictions, and the linker must be able to relocate
2342 an 8\dash byte address or 4\dash byte
2343 \addtoindexx{section offset!alignment of}
2344 section offset that occurs at an
2345 arbitrary alignment.
2347 \item For the \sixtyfourbitdwarfformat{} and a target architecture with
2348 32\dash bit addresses, an assembler or compiler must provide a
2349 way to produce 2\dash byte, 4\dash byte and 8\dash byte quantities without
2350 alignment restrictions, and the linker must be able to relocate
2351 a 4\dash byte address or 8\dash byte
2352 \addtoindexx{section offset!alignment of}
2353 section offset that occurs at an
2354 arbitrary alignment.
2356 \textit{It is expected that this will be required only for very large
2357 32\dash bit programs or by those architectures which support
2358 a mix of 32\dash bit and 64\dash bit code and data within the same
2361 \item For the \sixtyfourbitdwarfformat{} and a target architecture with
2362 64\dash bit addresses, an assembler or compiler must provide a
2363 way to produce 2\dash byte, 4\dash byte and 8\dash byte quantities without
2364 alignment restrictions, and the linker must be able to
2365 relocate an 8\dash byte address or
2366 \addtoindexx{section offset!alignment of}
2367 section offset that occurs at
2368 an arbitrary alignment.
2371 \section{Integer Representation Names}
2372 \label{datarep:integerrepresentationnames}
2374 The sizes of the integers used in the lookup by name, lookup
2375 by address, line number and call frame information sections
2377 Table \ref{tab:integerrepresentationnames}.
2380 \setlength{\extrarowheight}{0.1cm}
2381 \begin{longtable}{c|l}
2382 \caption{Integer representation names} \label{tab:integerrepresentationnames}\\
2383 \hline \bfseries Representation name&\bfseries Representation \\ \hline
2385 \bfseries Representation name&\bfseries Representation\\ \hline
2387 \hline \emph{Continued on next page}
2392 \addtoindex{sbyte}& signed, 1\dash byte integer \\
2393 \addtoindex{ubyte}&unsigned, 1\dash byte integer \\
2394 \addtoindex{uhalf}&unsigned, 2\dash byte integer \\
2395 \addtoindex{uword}&unsigned, 4\dash byte integer \\
2401 \section{Type Signature Computation}
2402 \label{datarep:typesignaturecomputation}
2404 A type signature is computed only by the DWARF producer;
2405 \addtoindexx{type signature computation}
2406 it is used by a DWARF consumer to resolve type references to
2407 the type definitions that are contained in
2408 \addtoindexx{type unit}
2411 The type signature for a type T0 is formed from the
2412 \addtoindex{MD5 hash}
2413 of a flattened description of the type. The flattened
2414 description of the type is a byte sequence derived from the
2415 DWARF encoding of the type as follows:
2416 \begin{enumerate}[1. ]
2418 \item Start with an empty sequence S and a list V of visited
2419 types, where V is initialized to a list containing the type
2420 T0 as its single element. Elements in V are indexed from 1,
2423 \item If the debugging information entry represents a type that
2424 is nested inside another type or a namespace, append to S
2425 the type\textquoteright s context as follows: For each surrounding type
2426 or namespace, beginning with the outermost such construct,
2427 append the letter 'C', the DWARF tag of the construct, and
2428 the name (taken from
2429 \addtoindexx{name attribute}
2430 the \livelink{chap:DWATname}{DW\_AT\_name} attribute) of the type
2431 \addtoindexx{name attribute}
2432 or namespace (including its trailing null byte).
2434 \item Append to S the letter 'D', followed by the DWARF tag of
2435 the debugging information entry.
2437 \item For each of the attributes in
2438 Table \refersec{tab:attributesusedintypesignaturecomputation}
2440 the debugging information entry, in the order listed,
2441 append to S a marker letter (see below), the DWARF attribute
2442 code, and the attribute value.
2445 \caption{Attributes used in type signature computation}
2446 \label{tab:attributesusedintypesignaturecomputation}
2447 \simplerule[\textwidth]
2449 \autocols[0pt]{c}{2}{l}{
2450 \livelink{chap:DWATname}{DW\_AT\_name},
2451 \livelink{chap:DWATaccessibility}{DW\_AT\_accessibility},
2452 \livelink{chap:DWATaddressclass}{DW\_AT\_address\_class},
2453 \livelink{chap:DWATallocated}{DW\_AT\_allocated},
2454 \livelink{chap:DWATartificial}{DW\_AT\_artificial},
2455 \livelink{chap:DWATassociated}{DW\_AT\_associated},
2456 \livelink{chap:DWATbinaryscale}{DW\_AT\_binary\_scale},
2457 \livelink{chap:DWATbitoffset}{DW\_AT\_bit\_offset},
2458 \livelink{chap:DWATbitsize}{DW\_AT\_bit\_size},
2459 \livelink{chap:DWATbitstride}{DW\_AT\_bit\_stride},
2460 \livelink{chap:DWATbytesize}{DW\_AT\_byte\_size},
2461 \livelink{chap:DWATbytestride}{DW\_AT\_byte\_stride},
2462 \livelink{chap:DWATconstexpr}{DW\_AT\_const\_expr},
2463 \livelink{chap:DWATconstvalue}{DW\_AT\_const\_value},
2464 \livelink{chap:DWATcontainingtype}{DW\_AT\_containing\_type},
2465 \livelink{chap:DWATcount}{DW\_AT\_count},
2466 \livelink{chap:DWATdatabitoffset}{DW\_AT\_data\_bit\_offset},
2467 \livelink{chap:DWATdatalocation}{DW\_AT\_data\_location},
2468 \livelink{chap:DWATdatamemberlocation}{DW\_AT\_data\_member\_location},
2469 \livelink{chap:DWATdecimalscale}{DW\_AT\_decimal\_scale},
2470 \livelink{chap:DWATdecimalsign}{DW\_AT\_decimal\_sign},
2471 \livelink{chap:DWATdefaultvalue}{DW\_AT\_default\_value},
2472 \livelink{chap:DWATdigitcount}{DW\_AT\_digit\_count},
2473 \livelink{chap:DWATdiscr}{DW\_AT\_discr},
2474 \livelink{chap:DWATdiscrlist}{DW\_AT\_discr\_list},
2475 \livelink{chap:DWATdiscrvalue}{DW\_AT\_discr\_value},
2476 \livelink{chap:DWATencoding}{DW\_AT\_encoding},
2477 \livelink{chap:DWATenumclass}{DW\_AT\_enum\_class},
2478 \livelink{chap:DWATendianity}{DW\_AT\_endianity},
2479 \livelink{chap:DWATexplicit}{DW\_AT\_explicit},
2480 \livelink{chap:DWATisoptional}{DW\_AT\_is\_optional},
2481 \livelink{chap:DWATlocation}{DW\_AT\_location},
2482 \livelink{chap:DWATlowerbound}{DW\_AT\_lower\_bound},
2483 \livelink{chap:DWATmutable}{DW\_AT\_mutable},
2484 \livelink{chap:DWATordering}{DW\_AT\_ordering},
2485 \livelink{chap:DWATpicturestring}{DW\_AT\_picture\_string},
2486 \livelink{chap:DWATprototyped}{DW\_AT\_prototyped},
2487 \livelink{chap:DWATsmall}{DW\_AT\_small},
2488 \livelink{chap:DWATsegment}{DW\_AT\_segment},
2489 \livelink{chap:DWATstringlength}{DW\_AT\_string\_length},
2490 \livelink{chap:DWATstringlengthbitsize}{DW\_AT\_string\_length\_bit\_size},
2491 \livelink{chap:DWATstringlengthbytesize}{DW\_AT\_string\_length\_byte\_size},
2492 \livelink{chap:DWATthreadsscaled}{DW\_AT\_threads\_scaled},
2493 \livelink{chap:DWATupperbound}{DW\_AT\_upper\_bound},
2494 \livelink{chap:DWATuselocation}{DW\_AT\_use\_location},
2495 \livelink{chap:DWATuseUTF8}{DW\_AT\_use\_UTF8},
2496 \livelink{chap:DWATvariableparameter}{DW\_AT\_variable\_parameter},
2497 \livelink{chap:DWATvirtuality}{DW\_AT\_virtuality},
2498 \livelink{chap:DWATvisibility}{DW\_AT\_visibility},
2499 \livelink{chap:DWATvtableelemlocation}{DW\_AT\_vtable\_elem\_location}
2502 \simplerule[\textwidth]
2505 Note that except for the initial
2506 \livelink{chap:DWATname}{DW\_AT\_name} attribute,
2507 \addtoindexx{name attribute}
2508 attributes are appended in order according to the alphabetical
2509 spelling of their identifier.
2511 If an implementation defines any vendor-specific attributes,
2512 any such attributes that are essential to the definition of
2513 the type should also be included at the end of the above list,
2514 in their own alphabetical suborder.
2516 An attribute that refers to another type entry T is processed
2517 as follows: (a) If T is in the list V at some V[x], use the
2518 letter 'R' as the marker and use the unsigned LEB128 encoding
2519 of x as the attribute value; otherwise, (b) use the letter 'T'
2520 as the marker, process the type T recursively by performing
2521 Steps 2 through 7, and use the result as the attribute value.
2523 Other attribute values use the letter 'A' as the marker, and
2524 the value consists of the form code (encoded as an unsigned
2525 LEB128 value) followed by the encoding of the value according
2526 to the form code. To ensure reproducibility of the signature,
2527 the set of forms used in the signature computation is limited
2528 to the following: \livelink{chap:DWFORMsdata}{DW\_FORM\_sdata},
2529 \livelink{chap:DWFORMflag}{DW\_FORM\_flag},
2530 \livelink{chap:DWFORMstring}{DW\_FORM\_string},
2531 and \livelink{chap:DWFORMblock}{DW\_FORM\_block}.
2533 \item If the tag in Step 3 is one of \livelink{chap:DWTAGpointertype}{DW\_TAG\_pointer\_type},
2534 \livelink{chap:DWTAGreferencetype}{DW\_TAG\_reference\_type},
2535 \livelink{chap:DWTAGrvaluereferencetype}{DW\_TAG\_rvalue\_reference\_type},
2536 \livelink{chap:DWTAGptrtomembertype}{DW\_TAG\_ptr\_to\_member\_type},
2537 or \livelink{chap:DWTAGfriend}{DW\_TAG\_friend}, and the referenced
2538 type (via the \livelink{chap:DWATtype}{DW\_AT\_type} or
2539 \livelink{chap:DWATfriend}{DW\_AT\_friend} attribute) has a
2540 \livelink{chap:DWATname}{DW\_AT\_name} attribute, append to S the letter 'N', the DWARF
2541 attribute code (\livelink{chap:DWATtype}{DW\_AT\_type} or
2542 \livelink{chap:DWATfriend}{DW\_AT\_friend}), the context of
2543 the type (according to the method in Step 2), the letter 'E',
2544 and the name of the type. For \livelink{chap:DWTAGfriend}{DW\_TAG\_friend}, if the referenced
2545 entry is a \livelink{chap:DWTAGsubprogram}{DW\_TAG\_subprogram}, the context is omitted and the
2546 name to be used is the ABI-specific name of the subprogram
2547 (e.g., the mangled linker name).
2550 \item If the tag in Step 3 is not one of \livelink{chap:DWTAGpointertype}{DW\_TAG\_pointer\_type},
2551 \livelink{chap:DWTAGreferencetype}{DW\_TAG\_reference\_type},
2552 \livelink{chap:DWTAGrvaluereferencetype}{DW\_TAG\_rvalue\_reference\_type},
2553 \livelink{chap:DWTAGptrtomembertype}{DW\_TAG\_ptr\_to\_member\_type}, or
2554 \livelink{chap:DWTAGfriend}{DW\_TAG\_friend}, but has
2555 a \livelink{chap:DWATtype}{DW\_AT\_type} attribute, or if the referenced type (via
2556 the \livelink{chap:DWATtype}{DW\_AT\_type} or
2557 \livelink{chap:DWATfriend}{DW\_AT\_friend} attribute) does not have a
2558 \livelink{chap:DWATname}{DW\_AT\_name} attribute, the attribute is processed according to
2559 the method in Step 4 for an attribute that refers to another
2563 \item Visit each child C of the debugging information
2564 entry as follows: If C is a nested type entry or a member
2565 function entry, and has
2566 a \livelink{chap:DWATname}{DW\_AT\_name} attribute, append to
2567 \addtoindexx{name attribute}
2568 S the letter 'S', the tag of C, and its name; otherwise,
2569 process C recursively by performing Steps 3 through 7,
2570 appending the result to S. Following the last child (or if
2571 there are no children), append a zero byte.
2576 For the purposes of this algorithm, if a debugging information
2578 \livelink{chap:DWATspecification}{DW\_AT\_specification}
2579 attribute that refers to
2580 another entry D (which has a
2581 \livelink{chap:DWATdeclaration}{DW\_AT\_declaration}
2583 then S inherits the attributes and children of D, and S is
2584 processed as if those attributes and children were present in
2585 the entry S. Exception: if a particular attribute is found in
2586 both S and D, the attribute in S is used and the corresponding
2587 one in D is ignored.
2589 DWARF tag and attribute codes are appended to the sequence
2590 as unsigned LEB128 values, using the values defined earlier
2593 \textit{A grammar describing this computation may be found in
2594 Appendix \refersec{app:typesignaturecomputationgrammar}.
2597 \textit{An attribute that refers to another type entry should
2598 be recursively processed or replaced with the name of the
2599 referent (in Step 4, 5 or 6). If neither treatment applies to
2600 an attribute that references another type entry, the entry
2601 that contains that attribute should not be considered for a
2602 separate \addtoindex{type unit}.}
2604 \textit{If a debugging information entry contains an attribute from
2605 the list above that would require an unsupported form, that
2606 entry should not be considered for a separate
2607 \addtoindex{type unit}.}
2609 \textit{A type should be considered for a separate
2610 \addtoindex{type unit} only
2611 if all of the type entries that it contains or refers to in
2612 Steps 6 and 7 can themselves each be considered for a separate
2613 \addtoindex{type unit}.}
2616 Where the DWARF producer may reasonably choose two or more
2617 different forms for a given attribute, it should choose
2618 the simplest possible form in computing the signature. (For
2619 example, a constant value should be preferred to a location
2620 expression when possible.)
2622 Once the string S has been formed from the DWARF encoding,
2623 an \addtoindex{MD5 hash} is computed for the string and the lower 64 bits
2624 are taken as the type signature.
2626 \textit{The string S is intended to be a flattened representation of
2627 the type that uniquely identifies that type (i.e., a different
2628 type is highly unlikely to produce the same string).}
2630 \textit{A debugging information entry should not be placed in a
2631 separate \addtoindex{type unit}
2632 if any of the following apply:}
2636 \item \textit{The entry has an attribute whose value is a location
2637 expression, and the location expression contains a reference to
2638 another debugging information entry (e.g., a \livelink{chap:DWOPcallref}{DW\_OP\_call\_ref}
2639 operator), as it is unlikely that the entry will remain
2640 identical across compilation units.}
2642 \item \textit{The entry has an attribute whose value refers
2643 to a code location or a \addtoindex{location list}.}
2645 \item \textit{The entry has an attribute whose value refers
2646 to another debugging information entry that does not represent
2652 \textit{Certain attributes are not included in the type signature:}
2655 \item \textit{The \livelink{chap:DWATdeclaration}{DW\_AT\_declaration} attribute is not included because it
2656 indicates that the debugging information entry represents an
2657 incomplete declaration, and incomplete declarations should
2659 \addtoindexx{type unit}
2660 separate type units.}
2662 \item \textit{The \livelink{chap:DWATdescription}{DW\_AT\_description} attribute is not included because
2663 it does not provide any information unique to the defining
2664 declaration of the type.}
2666 \item \textit{The \livelink{chap:DWATdeclfile}{DW\_AT\_decl\_file},
2667 \livelink{chap:DWATdeclline}{DW\_AT\_decl\_line}, and
2668 \livelink{chap:DWATdeclcolumn}{DW\_AT\_decl\_column} attributes are not included because they
2669 may vary from one source file to the next, and would prevent
2670 two otherwise identical type declarations from producing the
2671 \addtoindexx{MD5 hash}
2674 \item \textit{The \livelink{chap:DWATobjectpointer}{DW\_AT\_object\_pointer} attribute is not included
2675 because the information it provides is not necessary for the
2676 computation of a unique type signature.}
2680 \textit{Nested types and some types referred to by a debugging
2681 information entry are encoded by name rather than by recursively
2682 encoding the type to allow for cases where a complete definition
2683 of the type might not be available in all compilation units.}
2685 \textit{If a type definition contains the definition of a member function,
2686 it cannot be moved as is into a type unit, because the member function
2687 contains attributes that are unique to that compilation unit.
2688 Such a type definition can be moved to a type unit by rewriting the DIE tree,
2689 moving the member function declaration into a separate declaration tree,
2690 and replacing the function definition in the type with a non-defining
2691 declaration of the function (as if the function had been defined out of
2694 An example that illustrates the computation of an MD5 hash may be found in
2695 Appendix \refersec{app:usingtypeunits}.