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 \_lo\_user or \_hi\_user.
27 \textit{For example, for entry tags, the special
28 labels are \livetarg{chap:DWTAGlouser}{DW\-\_TAG\-\_lo\-\_user} and
29 \livetarg{chap:DWTAGhiuser}{DW\-\_TAG\-\_hi\-\_user}.}
31 range between \textit{prefix}\_lo\_user 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:
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 \addtoindex{initial length field} is one of the length fields that occur
98 of those DWARF sections that
100 (\addtoindex{.debug\_aranges},
101 \addtoindex{.debug\_info},
102 \addtoindex{.debug\_types},
103 \addtoindex{.debug\_line},
104 \addtoindex{.debug\_pubnames}, and
105 \addtoindex{.debug\_pubtypes}) or the length field
106 that occurs at the beginning of the CIE and FDE structures
107 in the \addtoindex{.debug\_frame} section.
109 In an \addtoindex{initial length field}, the values 0xfffffff0 through
110 0xffffffff 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 0xffffffff, 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}
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.]
157 \item In the 32\dash bit DWARF format, an
158 \addtoindex{initial length field}
160 \addtoindex{initial length field!encoding}
161 Section \refersec{datarep:initiallengthvalues})
162 is an unsigned 32\dash bit integer (which
163 must be less than 0xfffffff0); in the 64\dash bit DWARF format,
164 an \addtoindex{initial length field} is 96 bits in size,
167 \item The first 32\dash bits have the value 0xffffffff.
169 \item The following 64\dash bits contain the actual length
170 represented as an unsigned 64\dash bit integer.
173 \textit{This representation allows a DWARF consumer to dynamically
174 detect that a DWARF section contribution is using the 64\dash bit
175 format and to adapt its processing accordingly.}
177 \item Section offset and section length
178 \addtoindexx{section length!use in headers}
180 \addtoindexx{section offset!use in headers}
181 in the headers of DWARF sections (other
182 \addtoindex{initial length field}
184 \addtoindex{initial length}
185 fields) are listed following. In the 32\dash bit DWARF format these
186 are 32\dash bit unsigned integer values; in the 64\dash bit DWARF format,
188 \addtoindexx{section length!in .debug\_aranges header}
190 \addtoindexx{section length!in .debug\_pubnames header}
192 \addtoindexx{section length!in .debug\_pubtypes header}
193 unsigned integer values.
197 Section &Name & Role \\ \hline
198 \addtoindex{.debug\_ranges} & \addtoindex{debug\_info\_offset} & offset in \addtoindex{.debug\_info} \\
199 \addtoindex{.debug\_frame}/CIE & \addtoindex{CIE\_id} & CIE distinguished value \\
200 \addtoindex{.debug\_frame}/FDE & \addtoindex{CIE\_pointer} & offset in \addtoindex{.debug\_frame} \\
201 \addtoindex{.debug\_info} & \addtoindex{debug\_abbrev\_offset} & offset in \addtoindex{.debug\_abbrev} \\
202 \addtoindex{.debug\_line} & \addtoindex{header\_length} & length of header itself \\
203 \addtoindex{.debug\_pubnames} & \addtoindex{debug\_info\_offset} & offset in \addtoindex{.debug\_info} \\
204 & \addtoindex{debug\_info\_length} & length of \addtoindex{.debug\_info} \\
206 \addtoindex{.debug\_pubtypes} & \addtoindex{debug\_info\_offset} & offset in \addtoindex{.debug\_info} \\
207 & \addtoindex{debug\_info\_length} & length of \addtoindex{.debug\_info} \\
209 \addtoindex{.debug\_types} & \addtoindex{debug\_abbrev\_offset} & offset in \addtoindex{.debug\_info} \\
210 & \addtoindex{type\_offset} & offset in of \addtoindex{.debug\_types} \\
215 \textit{The CIE\_id field in a CIE structure must be 64 bits because
216 it overlays the CIE\_pointer in a FDE structure; this implicit
217 union must be accessed to distinguish whether a CIE or FDE is
218 present, consequently, these two fields must exactly overlay
219 each other (both offset and size).}
221 \item Within the body of the \addtoindex{.debug\_info} or \addtoindex{.debug\_types}
222 section, certain forms of attribute value depend on the choice
223 of DWARF format as follows. For the 32\dash bit DWARF format,
224 the value is a 32\dash bit unsigned integer; for the 64\dash bit DWARF
225 format, the value is a 64\dash bit unsigned integer.
228 Form & Role \\ \hline
229 \livelink{chap:DWFORMrefaddr}{DW\-\_FORM\-\_ref\-\_addr}& offset in \addtoindex{.debug\_info} \\
230 \livetarg{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}&
231 \parbox{5.5cm}{offset in a section other than \addtoindex{.debug\_info} or \addtoindex{.debug\_str}} \\
232 \livelink{chap:DWFORMstrp}{DW\-\_FORM\-\_strp}&offset in \addtoindex{.debug\_str} \\
233 \livelink{chap:DWOPcallref}{DW\-\_OP\-\_call\-\_ref}&offset in \addtoindex{.debug\_info} \\
237 \item Within the body of the \addtoindex{.debug\_pubnames} and
238 \addtoindex{.debug\_pubtypes}
239 sections, the representation of the first field
240 of each tuple (which represents an offset in the
241 \addtoindex{.debug\_info}
242 section) depends on the DWARF format as follows: in the
243 32\dash bit DWARF format, this field is a 32\dash bit unsigned integer;
244 in the 64\dash bit DWARF format, it is a 64\dash bit unsigned integer.
249 The 32\dash bit and 64\dash bit DWARF format conventions must not be
250 intermixed within a single compilation unit.
252 \textit{Attribute values and section header fields that represent
253 addresses in the target program are not affected by these
256 A DWARF consumer that supports the 64\dash bit DWARF format must
257 support executables in which some compilation units use the
258 32\dash bit format and others use the 64\dash bit format provided that
259 the combination links correctly (that is, provided that there
260 are no link\dash time errors due to truncation or overflow). (An
261 implementation is not required to guarantee detection and
262 reporting of all such errors.)
264 \textit{It is expected that DWARF producing compilers will not use
265 the 64\dash bit format by default. In most cases, the division of
266 even very large applications into a number of executable and
267 shared objects will suffice to assure that the DWARF sections
268 within each individual linked object are less than 4 GBytes
269 in size. However, for those cases where needed, the 64\dash bit
270 format allows the unusual case to be handled as well. Even
271 in this case, it is expected that only application supplied
272 objects will need to be compiled using the 64\dash bit format;
273 separate 32\dash bit format versions of system supplied shared
274 executable libraries can still be used.}
278 \section{Format of Debugging Information}
279 \label{datarep:formatofdebugginginformation}
281 For each compilation unit compiled with a DWARF producer,
282 a contribution is made to the \addtoindex{.debug\_info} section of
283 the object file. Each such contribution consists of a
284 compilation unit header
285 (see Section \refersec{datarep:compilationunitheader})
287 single \livelink{chap:DWTAGcompileunit}{DW\-\_TAG\-\_compile\-\_unit} or
288 \livelink{chap:DWTAGpartialunit}{DW\-\_TAG\-\_partial\-\_unit} debugging
289 information entry, together with its children.
291 For each type defined in a compilation unit, a contribution may
292 be made to the \addtoindex{.debug\_types}
293 section of the object file. Each
294 such contribution consists of a
295 \addtoindex{type unit} header
296 (see Section \refersec{datarep:typeunitheader})
297 followed by a \livelink{chap:DWTAGtypeunit}{DW\-\_TAG\-\_type\-\_unit} entry, together with
300 Each debugging information entry begins with a code that
301 represents an entry in a separate
302 \addtoindex{abbreviations table}. This
303 code is followed directly by a series of attribute values.
305 The appropriate entry in the
306 \addtoindex{abbreviations table} guides the
307 interpretation of the information contained directly in the
308 \addtoindex{.debug\_info} or
309 \addtoindex{.debug\_types} section.
312 Multiple debugging information entries may share the same
313 abbreviation table entry. Each compilation unit is associated
314 with a particular abbreviation table, but multiple compilation
315 units may share the same table.
316 \subsection{Unit Headers}
317 \label{datarep:unitheaders}
319 \subsubsection{Compilation Unit Header}
320 \label{datarep:compilationunitheader}
322 \begin{enumerate}[1.]
324 \item unit\_length (initial length) \\
325 \addtoindexx{unit\_length}
326 A 4\dash byte or 12\dash byte
327 \addtoindexx{initial length}
328 unsigned integer representing the length
329 of the \addtoindex{.debug\_info}
330 contribution for that compilation unit,
331 not including the length field itself. In the 32\dash bit DWARF
332 format, this is a 4\dash byte unsigned integer (which must be less
333 than 0xfffffff0); in the 64\dash bit DWARF format, this consists
334 of the 4\dash byte value 0xffffffff followed by an 8\dash byte unsigned
335 integer that gives the actual length
336 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
338 \item version (\addtoindex{uhalf})
339 A 2\dash byte unsigned integer representing the version of the
340 DWARF information for the compilation unit\addtoindexx{version number!compilation unit}
341 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
342 The value in this field is 4.
344 \item \addtoindex{debug\_abbrev\_offset} (section offset) \\
346 \addtoindexx{section offset!in .debug\_info header}
347 4\dash byte or 8\dash byte unsigned offset into the
348 \addtoindex{.debug\_abbrev}
349 section. This offset associates the compilation unit with a
350 particular set of debugging information entry abbreviations. In
351 the 32\dash bit DWARF format, this is a 4\dash byte unsigned length;
352 in the 64\dash bit DWARF format, this is an 8\dash byte unsigned length
353 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
355 \item address\_size (\addtoindex{ubyte}) \\
356 A 1\dash byte unsigned integer representing the size in bytes of
357 \addtoindexx{address\_size}
358 an address on the target architecture. If the system uses
359 \addtoindexx{address space!segmented}
360 segmented addressing, this value represents the size of the
361 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 \addtoindex{.debug\_types} section,
375 consists of the following information:
377 \begin{enumerate}[1.]
379 \item unit\_length (initial length) \\
380 \addtoindexx{unit\_length}
381 A 4\dash byte or 12\dash byte unsigned integer
382 \addtoindexx{initial length}
383 representing the length
384 of the \addtoindex{.debug\_types} contribution for that compilation unit,
385 not including the length field itself. In the 32\dash bit DWARF
386 format, this is a 4\dash byte unsigned integer (which must be
387 less than 0xfffffff0); in the 64\dash bit DWARF format, this
388 consists of the 4\dash byte value 0xffffffff followed by an
389 8\dash byte unsigned integer that gives the actual length
390 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
392 \item version (\addtoindex{uhalf})
393 A 2\dash byte unsigned integer representing the version of the
394 DWARF information for the
395 compilation unit\addtoindexx{version number!type unit}
396 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
397 The value in this field is 4.
399 \item \addtoindex{debug\_abbrev\_offset} (section offset) \\
401 \addtoindexx{section offset!in .debug\_types header}
402 4\dash byte or 8\dash byte unsigned offset into the
403 \addtoindex{.debug\_abbrev}
404 section. This offset associates the compilation unit with a
405 particular set of debugging information entry abbreviations. In
406 the 32\dash bit DWARF format, this is a 4\dash byte unsigned length;
407 in the 64\dash bit DWARF format, this is an 8\dash byte unsigned length
408 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
410 \item address\_size (ubyte) \\
411 A 1\dash byte unsigned integer representing the size
412 \addtoindexx{size of an address}
414 \addtoindexx{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.
421 \item type\_signature (8\dash byte unsigned integer) \\
422 \addtoindexx{type signature}
424 \addtoindexx{type\_signature}
425 64\dash bit unique signature of the type described in this type
428 \textit{An attribute that refers(using \livelink{chap:DWFORMrefsig8}{DW\-\_FORM\-\_ref\-\_sig8}) to
429 the primary type contained in
430 this \addtoindex{type unit} uses this value.}
433 \item type\_offset (section offset) \\
434 \addtoindexx{type\_offset}
435 A 4\dash byte or 8\dash byte unsigned offset
436 \addtoindexx{section offset!in .debug\_types header}
437 relative to the beginning
438 of the \addtoindex{type unit} header.
439 This offset refers to the debugging
440 information entry that describes the type. Because the type
441 may be nested inside a namespace or other structures, and may
442 contain references to other types that have not been placed in
443 separate type units, it is not necessarily either the first or
444 the only entry in the type unit. In the 32\dash bit DWARF format,
445 this is a 4\dash byte unsigned length; in the 64\dash bit DWARF format,
446 this is an 8\dash byte unsigned length
447 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
451 \subsection{Debugging Information Entry}
452 \label{datarep:debugginginformationentry}
454 Each debugging information entry begins with an unsigned LEB128
455 number containing the abbreviation code for the entry. This
456 code represents an entry within the abbreviations table
457 associated with the compilation unit containing this entry. The
458 abbreviation code is followed by a series of attribute values.
460 On some architectures, there are alignment constraints on
461 section boundaries. To make it easier to pad debugging
462 information sections to satisfy such constraints, the
463 abbreviation code 0 is reserved. Debugging information entries
464 consisting of only the abbreviation code 0 are considered
467 \subsection{Abbreviations Tables}
468 \label{datarep:abbreviationstables}
470 The abbreviations tables for all compilation units
471 are contained in a separate object file section called
472 \addtoindex{.debug\_abbrev}.
473 As mentioned before, multiple compilation
474 units may share the same abbreviations table.
476 The abbreviations table for a single compilation unit consists
477 of a series of abbreviation declarations. Each declaration
478 specifies the tag and attributes for a particular form of
479 debugging information entry. Each declaration begins with
480 an unsigned LEB128 number representing the abbreviation
481 code itself. It is this code that appears at the beginning
482 of a debugging information entry in the
483 \addtoindex{.debug\_info} or
484 \addtoindex{.debug\_types}
485 section. As described above, the abbreviation
486 code 0 is reserved for null debugging information entries. The
487 abbreviation code is followed by another unsigned LEB128
488 number that encodes the entry\textquoteright s tag. The encodings for the
489 tag names are given in
490 Table \refersec{tab:tagencodings}.
493 \setlength{\extrarowheight}{0.1cm}
494 \begin{longtable}{l|l}
496 \caption{Tag encodings} \label{tab:tagencodings} \\
497 \hline \bfseries Tag name&\bfseries Value\\ \hline
499 \bfseries Tag name&\bfseries Value \\ \hline
501 \hline \emph{Continued on next page}
504 \ddag \ \textit{New in \addtoindex{DWARF Version 4}}
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}&0x3f \\
562 \livelink{chap:DWTAGsharedtype}{DW\-\_TAG\-\_shared\-\_type}&0x40 \\
563 \livelink{chap:DWTAGtypeunit}{DW\-\_TAG\-\_type\-\_unit} \ddag &0x41 \\
564 \livelink{chap:DWTAGrvaluereferencetype}{DW\-\_TAG\-\_rvalue\-\_reference\-\_type} \ddag &0x42 \\
565 \livelink{chap:DWTAGtemplatealias}{DW\-\_TAG\-\_template\-\_alias} \ddag &0x43 \\
566 \livelink{chap:DWTAGlouser}{DW\-\_TAG\-\_lo\-\_user}&0x4080 \\
567 \livelink{chap:DWTAGhiuser}{DW\-\_TAG\-\_hi\-\_user}&0xffff \\
571 Following the tag encoding is a 1\dash byte value that determines
572 whether a debugging information entry using this abbreviation
573 has child entries or not. If the value is
574 \livetarg{chap:DWCHILDRENyes}{DW\-\_CHILDREN\-\_yes},
575 the next physically succeeding entry of any debugging
576 information entry using this abbreviation is the first
577 child of that entry. If the 1\dash byte value following the
578 abbreviation\textquoteright s tag encoding is
579 \livetarg{chap:DWCHILDRENno}{DW\-\_CHILDREN\-\_no}, the next
580 physically succeeding entry of any debugging information entry
581 using this abbreviation is a sibling of that entry. (Either
582 the first child or sibling entries may be null entries). The
583 encodings for the child determination byte are given in
584 Table \refersec{tab:childdeterminationencodings}
586 Section \refersec{chap:relationshipofdebugginginformationentries},
587 each chain of sibling entries is terminated by a null entry.)
590 \setlength{\extrarowheight}{0.1cm}
591 \begin{longtable}{l|l}
592 \caption{Child determination encodings}
593 \label{tab:childdeterminationencodings}
594 \addtoindexx{Child determination encodings} \\
595 \hline \bfseries Children determination name&\bfseries Value \\ \hline
597 \bfseries Children determination name&\bfseries Value \\ \hline
599 \hline \emph{Continued on next page}
603 \livelink{chap:DWCHILDRENno}{DW\-\_CHILDREN\-\_no}&0x00 \\
604 \livelink{chap:DWCHILDRENyes}{DW\-\_CHILDREN\-\_yes}&0x01 \\ \hline
608 Finally, the child encoding is followed by a series of
609 attribute specifications. Each attribute specification
610 consists of two parts. The first part is an unsigned LEB128
611 number representing the attribute\textquoteright s name. The second part
612 is an unsigned LEB128 number representing the attribute\textquoteright s
613 form. The series of attribute specifications ends with an
614 entry containing 0 for the name and 0 for the form.
617 \livetarg{chap:DWFORMindirect}{DW\-\_FORM\-\_indirect} is a special case. For
618 attributes with this form, the attribute value itself in the
619 \addtoindex{.debug\_info} or
620 \addtoindex{.debug\_types}
621 section begins with an unsigned
622 LEB128 number that represents its form. This allows producers
623 to choose forms for particular attributes
624 \addtoindexx{abbreviations table!dynamic forms in}
626 without having to add a new entry to the abbreviations table.
628 The abbreviations for a given compilation unit end with an
629 entry consisting of a 0 byte for the abbreviation code.
632 Appendix \refersec{app:compilationunitsandabbreviationstableexample}
633 for a depiction of the organization of the
634 debugging information.}
637 \subsection{Attribute Encodings}
638 \label{datarep:attributeencodings}
640 The encodings for the attribute names are given in
641 Table \refersec{tab:attributeencodings}.
643 The attribute form governs how the value of the attribute is
644 encoded. There are nine classes of form, listed below. Each
645 class is a set of forms which have related representations
646 and which are given a common interpretation according to the
647 attribute in which the form is used.
649 Form \livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}
651 \addtoindexx{rangelistptr class}
653 \addtoindexx{macptr class}
655 \addtoindexx{loclistptr class}
657 \addtoindexx{lineptr class}
658 namely \livelink{chap:lineptr}{lineptr},
659 \livelink{chap:loclistptr}{loclistptr},
660 \livelink{chap:macptr}{macptr} or
661 \livelink{chap:rangelistptr}{rangelistptr}; the list
662 of classes allowed by the applicable attribute in
663 Table \refersec{tab:attributeencodings}
664 determines the class of the form.
666 \textit{In DWARF V3 the forms \livelink{chap:DWFORMdata4}{DW\-\_FORM\-\_data4} and
667 \livelink{chap:DWFORMdata8}{DW\-\_FORM\-\_data8} were
668 \addtoindexx{lineptr class}
670 \addtoindexx{rangelistptr class}
672 \addtoindexx{macptr class}
674 \addtoindexx{loclistptr class}
675 class constant \addtoindexx{constant class}
676 or one of the classes
677 \livelink{chap:lineptr}{lineptr},
678 \livelink{chap:loclistptr}{loclistptr},
679 \livelink{chap:macptr}{macptr} or
680 \livelink{chap:rangelistptr}{rangelistptr}, depending on context. In
682 \livelink{chap:DWFORMdata4}{DW\-\_FORM\-\_data4} and
683 \livelink{chap:DWFORMdata8}{DW\-\_FORM\-\_data8} are members of class
684 constant in all cases.
686 \livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset} replaces
687 their usage for the other classes.}
689 Each possible form belongs to one or more of the following classes:
692 \item \livelinki{chap:DWATaddressclass}{address}{address class} \\
693 Represented as an object of appropriate size to hold an
694 address on the target machine
695 (\livetarg{chap:DWFORMaddr}{DW\-\_FORM\-\_addr}).
697 encoded in the compilation unit header
698 (see Section \refersec{datarep:compilationunitheader}).
699 This address is relocatable in a relocatable object file and
700 is relocated in an executable file or shared object.
702 \item \livelink{chap:block}{block} \\
703 Blocks come in four forms:
705 \begin{myindentpara}{1cm}
706 A 1\dash byte length followed by 0 to 255 contiguous information
707 bytes (\livetarg{chap:DWFORMblock1}{DW\-\_FORM\-\_block1}).
710 \begin{myindentpara}{1cm}
711 A 2\dash byte length followed by 0 to 65,535 contiguous information
712 bytes (\livetarg{chap:DWFORMblock2}{DW\-\_FORM\-\_block2}).
716 \begin{myindentpara}{1cm}
717 A 4\dash byte length followed by 0 to 4,294,967,295 contiguous
718 information bytes (\livetarg{chap:DWFORMblock4}{DW\-\_FORM\-\_block4}).
722 \begin{myindentpara}{1cm}
723 An unsigned LEB128 length followed by the number of bytes
724 specified by the length (\livetarg{chap:DWFORMblock}{DW\-\_FORM\-\_block}).
727 In all forms, the length is the number of information bytes
728 that follow. The information bytes may contain any mixture
729 of relocated (or relocatable) addresses, references to other
730 debugging information entries or data bytes.
733 There are six forms of constants. There are fixed length
734 constant data forms for one, two, four and eight byte values
736 \livetarg{chap:DWFORMdata1}{DW\-\_FORM\-\_data1},
737 \livetarg{chap:DWFORMdata2}{DW\-\_FORM\-\_data2},
738 \livetarg{chap:DWFORMdata4}{DW\-\_FORM\-\_data4},
739 and \livetarg{chap:DWFORMdata8}{DW\-\_FORM\-\_data8}).
740 There are also variable length constant
741 data forms encoded using LEB128 numbers (see below). Both
742 signed (\livetarg{chap:DWFORMsdata}{DW\-\_FORM\-\_sdata}) and unsigned
743 (\livetarg{chap:DWFORMudata}{DW\-\_FORM\-\_udata}) variable
744 length constants are available
746 The data in \livelink{chap:DWFORMdata1}{DW\-\_FORM\-\_data1},
747 \livelink{chap:DWFORMdata2}{DW\-\_FORM\-\_data2},
748 \livelink{chap:DWFORMdata4}{DW\-\_FORM\-\_data4} and
749 \livelink{chap:DWFORMdata8}{DW\-\_FORM\-\_data8}
750 can be anything. Depending on context, it may
751 be a signed integer, an unsigned integer, a floating\dash point
752 constant, or anything else. A consumer must use context to
753 know how to interpret the bits, which if they are target
754 machine data (such as an integer or floating point constant)
755 will be in target machine byte\dash order.
757 \textit{If one of the \livetarg{chap:DWFORMdata}{DW\-\_FORM\-\_data}\textless n\textgreater
758 forms is used to represent a
759 signed or unsigned integer, it can be hard for a consumer
760 to discover the context necessary to determine which
761 interpretation is intended. Producers are therefore strongly
762 encouraged to use \livelink{chap:DWFORMsdata}{DW\-\_FORM\-\_sdata} or
763 \livelink{chap:DWFORMudata}{DW\-\_FORM\-\_udata} for signed and
764 unsigned integers respectively, rather than
765 \livelink{chap:DWFORMdata}{DW\-\_FORM\-\_data}\textless n\textgreater.}
768 \item \livelink{chap:exprloc}{exprloc} \\
769 This is an unsigned LEB128 length followed by the
770 number of information bytes specified by the length
771 (\livetarg{chap:DWFORMexprloc}{DW\-\_FORM\-\_exprloc}).
772 The information bytes contain a DWARF
774 (see Section \refersec{chap:dwarfexpressions})
775 or location description
776 (see Section \refersec{chap:locationdescriptions}).
778 \item \livelink{chap:flag}{flag} \\
779 A flag \addtoindexx{flag class}
780 is represented explicitly as a single byte of data
781 (\livetarg{chap:DWFORMflag}{DW\-\_FORM\-\_flag}) or
782 implicitly (\livetarg{chap:DWFORMflagpresent}{DW\-\_FORM\-\_flag\-\_present}).
784 first case, if the \nolink{flag} has value zero, it indicates the
785 absence of the attribute; if the \nolink{flag} has a non\dash zero value,
786 it indicates the presence of the attribute. In the second
787 case, the attribute is implicitly indicated as present, and
788 no value is encoded in the debugging information entry itself.
790 \item \livelink{chap:lineptr}{lineptr} \\
791 This is an offset into
792 \addtoindexx{section offset!in class lineptr value}
794 \addtoindex{.debug\_line} section
795 (\livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}).
796 It consists of an offset from the
798 \addtoindex{.debug\_line}
799 section to the first byte of
800 the data making up the line number list for the compilation
802 It is relocatable in a relocatable object file, and
803 relocated in an executable or shared object. In the 32\dash bit
804 DWARF format, this offset is a 4\dash byte unsigned value;
805 in the 64\dash bit DWARF format, it is an 8\dash byte unsigned value
806 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
809 \item \livelink{chap:loclistptr}{loclistptr} \\
810 This is an offset into the
811 \addtoindex{.debug\_loc}
813 (\livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}).
814 It consists of an offset from the
815 \addtoindexx{section offset!in class loclistptr value}
817 \addtoindex{.debug\_loc}
818 section to the first byte of
819 the data making up the
820 \addtoindex{location list} for the compilation
822 It is relocatable in a relocatable object file, and
823 relocated in an executable or shared object. In the 32\dash bit
824 DWARF format, this offset is a 4\dash byte unsigned value;
825 in the 64\dash bit DWARF format, it is an 8\dash byte unsigned value
826 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
829 \item \livelink{chap:macptr}{macptr} \\
831 \addtoindexx{section offset!in class macptr value}
833 \addtoindex{.debug\_macinfo} section
834 (\livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}).
835 It consists of an offset from the
836 beginning of the \addtoindex{.debug\_macinfo}
837 section to the first byte of
838 the data making up the macro information list for the compilation
840 It is relocatable in a relocatable object file, and
841 relocated in an executable or shared object. In the 32\dash bit
842 DWARF format, this offset is a 4\dash byte unsigned value;
843 in the 64\dash bit DWARF format, it is an 8\dash byte unsigned value
844 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
847 \item \livelink{chap:rangelistptr}{rangelistptr} \\
849 \addtoindexx{section offset!in class rangelistptr value}
850 offset into the \addtoindex{.debug\_ranges} section
851 (\livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}).
853 offset from the beginning of the
854 \addtoindex{.debug\_ranges} section
855 to the beginning of the non\dash contiguous address ranges
856 information for the referencing entity.
858 a relocatable object file, and relocated in an executable or
859 shared object. In the 32\dash bit DWARF format, this offset
860 is a 4\dash byte unsigned value; in the 64\dash bit DWARF
861 format, it is an 8\dash byte unsigned value (see Section
862 \refersec{datarep:32bitand64bitdwarfformats}).
865 \textit{Because classes \livelink{chap:lineptr}{lineptr},
866 \livelink{chap:loclistptr}{loclistptr},
867 \livelink{chap:macptr}{macptr} and
868 \livelink{chap:rangelistptr}{rangelistptr}
869 share a common representation, it is not possible for an
870 attribute to allow more than one of these classes}
875 There are three types of reference.
878 \addtoindexx{reference class}
879 first type of reference can identify any debugging
880 information entry within the containing unit.
883 \addtoindexx{section offset!in class reference value}
884 offset from the first byte of the compilation
885 header for the compilation unit containing the reference. There
886 are five forms for this type of reference. There are fixed
887 length forms for one, two, four and eight byte offsets
888 (respectively, \livetarg{chap:DWFORMref1}{DW\-\_FORM\-\_ref1},
889 \livetarg{chap:DWFORMref2}{DW\-\_FORM\-\_ref2},
890 \livetarg{chap:DWFORMref4}{DW\-\_FORM\-\_ref4},
891 and \livetarg{chap:DWFORMref8}{DW\-\_FORM\-\_ref8}).
892 There is also an unsigned variable
893 length offset encoded form that uses unsigned LEB128 numbers
894 (\livetarg{chap:DWFORMrefudata}{DW\-\_FORM\-\_ref\-\_udata}).
895 Because this type of reference is within
896 the containing compilation unit no relocation of the value
899 The second type of reference can identify any debugging
900 information entry within a
901 \addtoindex{.debug\_info} section; in particular,
902 it may refer to an entry in a different compilation unit
903 from the unit containing the reference, and may refer to an
904 entry in a different shared object. This type of reference
905 (\livetarg{chap:DWFORMrefaddr}{DW\-\_FORM\-\_ref\-\_addr})
906 is an offset from the beginning of the
907 \addtoindex{.debug\_info}
908 section of the target executable or shared object;
909 it is relocatable in a relocatable object file and frequently
910 relocated in an executable file or shared object. For
911 references from one shared object or static executable file
912 to another, the relocation and identification of the target
913 object must be performed by the consumer. In the 32\dash bit DWARF
914 format, this offset is a 4\dash byte unsigned value;
915 in the 64\dash bit DWARF format, it is an 8\dash byte
917 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
919 \textit{A debugging information entry that may be referenced by
920 another compilation unit using
921 \livelink{chap:DWFORMrefaddr}{DW\-\_FORM\-\_ref\-\_addr} must have a
922 global symbolic name.}
924 \textit{For a reference from one executable or shared object to
925 another, the reference is resolved by the debugger to identify
926 the shared object or executable and the offset into that
927 object\textquoteright s \addtoindex{.debug\_info}
928 section in the same fashion as the run
929 time loader, either when the debug information is first read,
930 or when the reference is used.}
932 The third type of reference can identify any debugging
933 information type entry that has been placed in its own
934 \addtoindex{type unit}. This type of
935 reference (\livetarg{chap:DWFORMrefsig8}{DW\-\_FORM\-\_ref\-\_sig8}) is the
936 \addtoindexx{type signature}
937 64\dash bit type signature
938 (see Section \refersec{datarep:typesignaturecomputation})
942 \textit{The use of compilation unit relative references will reduce the
943 number of link\dash time relocations and so speed up linking. The
944 use of the second and third type of reference allows for the
945 sharing of information, such as types, across compilation
948 \textit{A reference to any kind of compilation unit identifies the
949 debugging information entry for that unit, not the preceding
953 A string is a sequence of contiguous non\dash null bytes followed by
955 \addtoindexx{string class}
956 A string may be represented immediately in the
957 debugging information entry itself
958 (\livetarg{chap:DWFORMstring}{DW\-\_FORM\-\_string}), or may
960 \addtoindexx{section offset!in class string value}
961 offset into a string table contained in
962 the \addtoindex{.debug\_str} section of the object file
963 (\livetarg{chap:DWFORMstrp}{DW\-\_FORM\-\_strp}). In
964 the 32\dash bit DWARF format, the representation of a
965 \livelink{chap:DWFORMstrp}{DW\-\_FORM\-\_strp}
966 value is a 4\dash byte unsigned offset; in the 64\dash bit DWARF format,
967 it is an 8\dash byte unsigned offset
968 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
970 If the \livelink{chap:DWATuseUTF8}{DW\-\_AT\-\_use\-\_UTF8}
971 \addtoindexx{use UTF8 attribute}\addtoindexx{UTF-8} attribute is specified for the
972 compilation unit entry, string values are encoded using the
973 UTF\dash 8 (\addtoindex{Unicode} Transformation Format\dash 8) from the Universal
974 Character Set standard (ISO/IEC 10646\dash 1:1993). Otherwise,
975 the string representation is unspecified.
977 \textit{The \addtoindex{Unicode} Standard Version 3 is fully compatible with
978 ISO/IEC 10646\dash 1:1993. It contains all the same characters
979 and encoding points as ISO/IEC 10646, as well as additional
980 information about the characters and their use.}
982 \textit{Earlier versions of DWARF did not specify the representation
983 of strings; for compatibility, this version also does
984 not. However, the UTF\dash 8 representation is strongly recommended.}
988 In no case does an attribute use
989 \addtoindexx{rangelistptr class}
991 \addtoindexx{loclistptr class}
993 \addtoindexx{lineptr class}
995 \addtoindexx{macptr class}
996 classes \livelink{chap:lineptr}{lineptr},
997 \livelink{chap:loclistptr}{loclistptr}, \livelink{chap:macptr}{macptr} or
998 \livelink{chap:rangelistptr}{rangelistptr} to point into either the
999 \addtoindex{.debug\_info} or \addtoindex{.debug\_str} section.
1001 The form encodings are listed in
1002 Table \refersec{tab:attributeformencodings}.
1006 \setlength{\extrarowheight}{0.1cm}
1007 \begin{longtable}{l|l|l}
1008 \caption{Attribute encodings}
1009 \label{tab:attributeencodings}
1010 \addtoindexx{attribute encodings} \\
1011 \hline \bfseries Attribute name&\bfseries Value &\bfseries Classes \\ \hline
1013 \bfseries Attribute name&\bfseries Value &\bfseries Classes\\ \hline
1015 \hline \emph{Continued on next page}
1018 \ddag \ \textit{New in \addtoindex{DWARF Version 4}}
1020 \livelink{chap:DWATsibling}{DW\-\_AT\-\_sibling}&0x01&reference
1021 \addtoindexx{sibling attribute!encoding} \\
1022 \livelink{chap:DWATlocation}{DW\-\_AT\-\_location}&0x02&\livelink{chap:exprloc}{exprloc},
1023 \livelink{chap:loclistptr}{loclistptr}\addtoindex{location attribute!encoding} \\
1024 \livelink{chap:DWATname}{DW\-\_AT\-\_name}&0x03&string
1025 \addtoindexx{name attribute!encoding} \\
1026 \livelink{chap:DWATordering}{DW\-\_AT\-\_ordering}&0x09&constant
1027 \addtoindexx{ordering attribute!encoding} \\
1028 \livelink{chap:DWATbytesize}{DW\-\_AT\-\_byte\-\_size}&0x0b&constant, \livelink{chap:exprloc}{exprloc},
1029 reference \addtoindexx{byte size attribute!encoding} \\
1030 \livelink{chap:DWATbitoffset}{DW\-\_AT\-\_bit\-\_offset}&0x0c&constant,
1031 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{bit offset attribute!encoding} \\
1032 \livelink{chap:DWATbitsize}{DW\-\_AT\-\_bit\-\_size}&0x0d&constant,
1033 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{bit size attribute!encoding} \\
1034 \livelink{chap:DWATstmtlist}{DW\-\_AT\-\_stmt\-\_list}&0x10&\livelink{chap:lineptr}{lineptr}
1035 \addtoindex{statement list attribute!encoding} \\
1036 \livelink{chap:DWATlowpc}{DW\-\_AT\-\_low\-\_pc}&0x11&address
1037 \addtoindexx{low PC attribute!encoding} \\
1038 \livelink{chap:DWAThighpc}{DW\-\_AT\-\_high\-\_pc}&0x12&address, constant
1039 \addtoindexx{high PC attribute!encoding} \\
1040 \livelink{chap:DWATlanguage}{DW\-\_AT\-\_language}&0x13&constant
1041 \addtoindexx{language attribute!encoding} \\
1042 \livelink{chap:DWATdiscr}{DW\-\_AT\-\_discr}&0x15&reference
1043 \addtoindexx{discriminant attribute!encoding} \\
1044 \livelink{chap:DWATdiscrvalue}{DW\-\_AT\-\_discr\-\_value}&0x16&constant
1045 \addtoindexx{discriminant value attribute!encoding} \\
1046 \livelink{chap:DWATvisibility}{DW\-\_AT\-\_visibility}&0x17&constant
1047 \addtoindexx{visibility attribute!encoding} \\
1048 \livelink{chap:DWATimport}{DW\-\_AT\-\_import}&0x18&reference
1049 \addtoindexx{import attribute!encoding} \\
1050 \livelink{chap:DWATstringlength}{DW\-\_AT\-\_string\-\_length}&0x19&\livelink{chap:exprloc}{exprloc},
1051 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{string length attribute!encoding} \\
1052 \livelink{chap:DWATcommonreference}{DW\-\_AT\-\_common\-\_reference}&0x1a&reference
1053 \addtoindexx{common reference attribute!encoding} \\
1054 \livelink{chap:DWATcompdir}{DW\-\_AT\-\_comp\-\_dir}&0x1b&string
1055 \addtoindexx{compilation directory attribute!encoding} \\
1056 \livelink{chap:DWATconstvalue}{DW\-\_AT\-\_const\-\_value}&0x1c&\livelink{chap:block}{block}, constant, string
1057 \addtoindexx{constant value attribute!encoding} \\
1058 \livelink{chap:DWATcontainingtype}{DW\-\_AT\-\_containing\-\_type}&0x1d&reference
1059 \addtoindexx{containing type attribute!encoding} \\
1060 \livelink{chap:DWATdefaultvalue}{DW\-\_AT\-\_default\-\_value}&0x1e&reference
1061 \addtoindexx{default value attribute!encoding} \\
1062 \livelink{chap:DWATinline}{DW\-\_AT\-\_inline}&0x20&constant
1063 \addtoindexx{inline attribute!encoding} \\
1064 \livelink{chap:DWATisoptional}{DW\-\_AT\-\_is\-\_optional}&0x21&\livelink{chap:flag}{flag}
1065 \addtoindexx{is optional attribute!encoding} \\
1066 \livelink{chap:DWATlowerbound}{DW\-\_AT\-\_lower\-\_bound}&0x22&constant,
1067 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{lower bound attribute!encoding} \\
1068 \livelink{chap:DWATproducer}{DW\-\_AT\-\_producer}&0x25&string \addtoindexx{producer attribute!encoding} \\
1069 \livelink{chap:DWATprototyped}{DW\-\_AT\-\_prototyped}&0x27&\livelink{chap:flag}{flag}
1070 \addtoindexx{prototyped attribute!encoding} \\
1071 \livelink{chap:DWATreturnaddr}{DW\-\_AT\-\_return\-\_addr}&0x2a&\livelink{chap:exprloc}{exprloc},
1072 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{return address attribute!encoding} \\
1073 % FIXME: lower case , not Constant
1074 \livelink{chap:DWATstartscope}{DW\-\_AT\-\_start\-\_scope}&0x2c&Constant,
1075 \livelink{chap:rangelistptr}{rangelistptr} \addtoindexx{start scope attribute!encoding} \\
1076 \livelink{chap:DWATbitstride}{DW\-\_AT\-\_bit\-\_stride}&0x2e&constant,
1077 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{bit stride attribute!encoding} \\
1078 \livelink{chap:DWATupperbound}{DW\-\_AT\-\_upper\-\_bound}&0x2f&constant,
1079 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{upper bound attribute!encoding} \\
1080 \livelink{chap:DWATabstractorigin}{DW\-\_AT\-\_abstract\-\_origin}&0x31&reference
1081 \addtoindexx{abstract origin attribute!encoding} \\
1082 \livelink{chap:DWATaccessibility}{DW\-\_AT\-\_accessibility}&0x32&constant
1083 \addtoindexx{accessibility attribute!encoding} \\
1084 \livelink{chap:DWATaddressclass}{DW\-\_AT\-\_address\-\_class}&0x33&constant
1085 \addtoindexx{address class attribute!encoding} \\
1086 \livelink{chap:DWATartificial}{DW\-\_AT\-\_artificial}&0x34&\livelink{chap:flag}{flag}
1087 \addtoindexx{artificial attribute!encoding} \\
1088 \livelink{chap:DWATbasetypes}{DW\-\_AT\-\_base\-\_types}&0x35&reference
1089 \addtoindexx{base types attribute!encoding} \\
1090 \livelink{chap:DWATcallingconvention}{DW\-\_AT\-\_calling\-\_convention}&0x36&constant
1091 \addtoindexx{calling convention attribute!encoding} \\
1092 \livelink{chap:DWATcount}{DW\-\_AT\-\_count}&0x37&constant, \livelink{chap:exprloc}{exprloc}, reference
1093 \addtoindexx{count attribute!encoding} \\
1094 \livelink{chap:DWATdatamemberlocation}{DW\-\_AT\-\_data\-\_member\-\_location}&0x38&constant,
1095 \livelink{chap:exprloc}{exprloc}, \livelink{chap:loclistptr}{loclistptr}
1096 \addtoindexx{data member attribute!encoding} \\
1097 \livelink{chap:DWATdeclcolumn}{DW\-\_AT\-\_decl\-\_column}&0x39&constant
1098 \addtoindexx{declaration column attribute!encoding} \\
1099 \livelink{chap:DWATdeclfile}{DW\-\_AT\-\_decl\-\_file}&0x3a&constant
1100 \addtoindexx{declaration file attribute!encoding} \\
1101 \livelink{chap:DWATdeclline}{DW\-\_AT\-\_decl\-\_line}&0x3b&constant
1102 \addtoindexx{declaration line attribute!encoding} \\
1103 \livelink{chap:DWATdeclaration}{DW\-\_AT\-\_declaration}&0x3c&\livelink{chap:flag}{flag}
1104 \addtoindexx{declaration attribute!encoding} \\
1105 \livelink{chap:DWATdiscrlist}{DW\-\_AT\-\_discr\-\_list}&0x3d&\livelink{chap:block}{block}
1106 \addtoindexx{discriminant list attribute!encoding} \\
1107 \livelink{chap:DWATencoding}{DW\-\_AT\-\_encoding}&0x3e&constant
1108 \addtoindexx{encoding attribute!encoding} \\
1109 \livelink{chap:DWATexternal}{DW\-\_AT\-\_external}&0x3f&\livelink{chap:flag}{flag}
1110 \addtoindexx{external attribute!encoding} \\
1111 \livelink{chap:DWATframebase}{DW\-\_AT\-\_frame\-\_base}&0x40&\livelink{chap:exprloc}{exprloc},
1112 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{frame base attribute!encoding} \\
1113 \livelink{chap:DWATfriend}{DW\-\_AT\-\_friend}&0x41&reference
1114 \addtoindexx{friend attribute!encoding} \\
1115 \livelink{chap:DWATidentifiercase}{DW\-\_AT\-\_identifier\-\_case}&0x42&constant
1116 \addtoindexx{identifier case attribute!encoding} \\
1117 \livelink{chap:DWATmacroinfo}{DW\-\_AT\-\_macro\-\_info}&0x43&\livelink{chap:macptr}{macptr}
1118 \addtoindexx{macro information attribute!encoding} \\
1119 \livelink{chap:DWATnamelistitem}{DW\-\_AT\-\_namelist\-\_item}&0x44&reference
1120 \addtoindexx{name list item attribute!encoding} \\
1121 \livelink{chap:DWATpriority}{DW\-\_AT\-\_priority}&0x45&reference
1122 \addtoindexx{priority attribute!encoding} \\
1123 \livelink{chap:DWATsegment}{DW\-\_AT\-\_segment}&0x46&\livelink{chap:exprloc}{exprloc},
1124 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{segment attribute!encoding} \\
1125 \livelink{chap:DWATspecification}{DW\-\_AT\-\_specification}&0x47&reference
1126 \addtoindexx{specification attribute!encoding} \\
1127 \livelink{chap:DWATstaticlink}{DW\-\_AT\-\_static\-\_link}&0x48&\livelink{chap:exprloc}{exprloc},
1128 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{static link attribute!encoding} \\
1129 \livelink{chap:DWATtype}{DW\-\_AT\-\_type}&0x49&reference
1130 \addtoindexx{type attribute!encoding} \\
1131 \livelink{chap:DWATuselocation}{DW\-\_AT\-\_use\-\_location}&0x4a&\livelink{chap:exprloc}{exprloc},
1132 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{location list attribute!encoding} \\
1133 \livelink{chap:DWATvariableparameter}{DW\-\_AT\-\_variable\-\_parameter}&0x4b&\livelink{chap:flag}{flag}
1134 \addtoindexx{variable parameter attribute!encoding} \\
1135 \livelink{chap:DWATvirtuality}{DW\-\_AT\-\_virtuality}&0x4c&constant
1136 \addtoindexx{virtuality attribute!encoding} \\
1137 \livelink{chap:DWATvtableelemlocation}{DW\-\_AT\-\_vtable\-\_elem\-\_location}&0x4d&\livelink{chap:exprloc}{exprloc},
1138 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{vtable element location attribute!encoding} \\
1140 \livelink{chap:DWATallocated}{DW\-\_AT\-\_allocated}&0x4e&constant, \livelink{chap:exprloc}{exprloc},
1141 reference \addtoindexx{allocated attribute!encoding} \\
1142 \livelink{chap:DWATassociated}{DW\-\_AT\-\_associated}&0x4f&constant, \livelink{chap:exprloc}{exprloc},
1143 reference \addtoindexx{associated attribute!encoding} \\
1144 \livelink{chap:DWATdatalocation}{DW\-\_AT\-\_data\-\_location}&0x50&\livelink{chap:exprloc}{exprloc}
1145 \addtoindexx{data location attribute!encoding} \\
1146 \livelink{chap:DWATbytestride}{DW\-\_AT\-\_byte\-\_stride}&0x51&constant, \livelink{chap:exprloc}{exprloc},
1147 reference \addtoindexx{byte stride attribute!encoding} \\
1148 \livelink{chap:DWATentrypc}{DW\-\_AT\-\_entry\-\_pc}&0x52&address
1149 \addtoindexx{entry pc attribute!encoding} \\
1150 \livelink{chap:DWATuseUTF8}{DW\-\_AT\-\_use\-\_UTF8}&0x53&\livelink{chap:flag}{flag}
1151 \addtoindexx{use UTF8 attribute!encoding}\addtoindex{UTF-8} \\
1152 \livelink{chap:DWATextension}{DW\-\_AT\-\_extension}&0x54&reference
1153 \addtoindexx{extension attribute!encoding} \\
1154 \livelink{chap:DWATranges}{DW\-\_AT\-\_ranges}&0x55&\livelink{chap:rangelistptr}{rangelistptr}
1155 \addtoindexx{ranges attribute!encoding} \\
1156 \livelink{chap:DWATtrampoline}{DW\-\_AT\-\_trampoline}&0x56&address, \livelink{chap:flag}{flag},
1157 reference, string \addtoindexx{trampoline attribute!encoding} \\
1158 \livelink{chap:DWATcallcolumn}{DW\-\_AT\-\_call\-\_column}&0x57&constant
1159 \addtoindexx{call column attribute!encoding} \\
1160 \livelink{chap:DWATcallfile}{DW\-\_AT\-\_call\-\_file}&0x58&constant
1161 \addtoindexx{call file attribute!encoding} \\
1162 \livelink{chap:DWATcallline}{DW\-\_AT\-\_call\-\_line}&0x59&constant
1163 \addtoindexx{call line attribute!encoding} \\
1164 \livelink{chap:DWATdescription}{DW\-\_AT\-\_description}&0x5a&string
1165 \addtoindexx{description attribute!encoding} \\
1166 \livelink{chap:DWATbinaryscale}{DW\-\_AT\-\_binary\-\_scale}&0x5b&constant
1167 \addtoindexx{binary scale attribute!encoding} \\
1168 \livelink{chap:DWATdecimalscale}{DW\-\_AT\-\_decimal\-\_scale}&0x5c&constant
1169 \addtoindexx{decimal scale attribute!encoding} \\
1170 \livelink{chap:DWATsmall}{DW\-\_AT\-\_small} &0x5d&reference
1171 \addtoindexx{small attribute!encoding} \\
1172 \livelink{chap:DWATdecimalsign}{DW\-\_AT\-\_decimal\-\_sign}&0x5e&constant
1173 \addtoindexx{decimal scale attribute!encoding} \\
1174 \livelink{chap:DWATdigitcount}{DW\-\_AT\-\_digit\-\_count}&0x5f&constant
1175 \addtoindexx{digit count attribute!encoding} \\
1176 \livelink{chap:DWATpicturestring}{DW\-\_AT\-\_picture\-\_string}&0x60&string
1177 \addtoindexx{picture string attribute!encoding} \\
1178 \livelink{chap:DWATmutable}{DW\-\_AT\-\_mutable}&0x61&\livelink{chap:flag}{flag}
1179 \addtoindexx{mutable attribute!encoding} \\
1181 \livelink{chap:DWATthreadsscaled}{DW\-\_AT\-\_threads\-\_scaled}&0x62&\livelink{chap:flag}{flag}
1182 \addtoindexx{thread scaled attribute!encoding} \\
1183 \livelink{chap:DWATexplicit}{DW\-\_AT\-\_explicit}&0x63&\livelink{chap:flag}{flag}
1184 \addtoindexx{explicit attribute!encoding} \\
1185 \livelink{chap:DWATobjectpointer}{DW\-\_AT\-\_object\-\_pointer}&0x64&reference
1186 \addtoindexx{object pointer attribute!encoding} \\
1187 \livelink{chap:DWATendianity}{DW\-\_AT\-\_endianity}&0x65&constant
1188 \addtoindexx{endianity attribute!encoding} \\
1189 \livelink{chap:DWATelemental}{DW\-\_AT\-\_elemental}&0x66&\livelink{chap:flag}{flag}
1190 \addtoindexx{elemental attribute!encoding} \\
1191 \livelink{chap:DWATpure}{DW\-\_AT\-\_pure}&0x67&\livelink{chap:flag}{flag}
1192 \addtoindexx{pure attribute!encoding} \\
1193 \livelink{chap:DWATrecursive}{DW\-\_AT\-\_recursive}&0x68&\livelink{chap:flag}{flag}
1194 \addtoindexx{recursive attribute!encoding} \\
1195 \livelink{chap:DWATsignature}{DW\-\_AT\-\_signature} \ddag &0x69&reference
1196 \addtoindexx{signature attribute!encoding} \\
1197 \livelink{chap:DWATmainsubprogram}{DW\-\_AT\-\_main\-\_subprogram} \ddag &0x6a&\livelink{chap:flag}{flag}
1198 \addtoindexx{main subprogram attribute!encoding} \\
1199 \livelink{chap:DWATdatabitoffset}{DW\-\_AT\-\_data\-\_bit\-\_offset} \ddag &0x6b&constant
1200 \addtoindexx{data bit offset attribute!encoding} \\
1201 \livelink{chap:DWATconstexpr}{DW\-\_AT\-\_const\-\_expr} \ddag &0x6c&\livelink{chap:flag}{flag}
1202 \addtoindexx{constant expression attribute!encoding} \\
1203 \livelink{chap:DWATenumclass}{DW\-\_AT\-\_enum\-\_class} \ddag &0x6d&\livelink{chap:flag}{flag}
1204 \addtoindexx{enumeration class attribute!encoding} \\
1205 \livelink{chap:DWATlinkagename}{DW\-\_AT\-\_linkage\-\_name} \ddag &0x6e&string
1206 \addtoindexx{linkage name attribute!encoding} \\
1207 \livetarg{chap:DWATlouser}{DW\-\_AT\-\_lo\-\_user}&0x2000 & --- \addtoindexx{low user attribute encoding} \\
1208 \livetarg{chap:DWAThiuser}{DW\-\_AT\-\_hi\-\_user}&0x3fff& --- \addtoindexx{high user attribute encoding} \\
1214 \setlength{\extrarowheight}{0.1cm}
1215 \begin{longtable}{l|l|l}
1216 \caption{Attribute form encodings} \label{tab:attributeformencodings} \\
1217 \hline \bfseries Form name&\bfseries Value &\bfseries Classes \\ \hline
1219 \bfseries Form name&\bfseries Value &\bfseries Classes\\ \hline
1221 \hline \emph{Continued on next page}
1224 \ddag \ \textit{New in \addtoindex{DWARF Version 4}}
1226 \livelink{chap:DWFORMaddr}{DW\-\_FORM\-\_addr}&0x01&address \\
1227 \livelink{chap:DWFORMblock2}{DW\-\_FORM\-\_block2}&0x03&\livelink{chap:block}{block} \\
1228 \livelink{chap:DWFORMblock4}{DW\-\_FORM\-\_block4}&0x04&\livelink{chap:block}{block} \\
1229 \livelink{chap:DWFORMdata2}{DW\-\_FORM\-\_data2}&0x05&constant \\
1230 \livelink{chap:DWFORMdata4}{DW\-\_FORM\-\_data4}&0x06&constant \\
1231 \livelink{chap:DWFORMdata8}{DW\-\_FORM\-\_data8}&0x07&constant \\
1232 \livelink{chap:DWFORMstring}{DW\-\_FORM\-\_string}&0x08&string \\
1233 \livelink{chap:DWFORMblock}{DW\-\_FORM\-\_block}&0x09&\livelink{chap:block}{block} \\
1234 \livelink{chap:DWFORMblock1}{DW\-\_FORM\-\_block1}&0x0a&\livelink{chap:block}{block} \\
1235 \livelink{chap:DWFORMdata1}{DW\-\_FORM\-\_data1}&0x0b&constant \\
1236 \livelink{chap:DWFORMflag}{DW\-\_FORM\-\_flag}&0x0c&\livelink{chap:flag}{flag} \\
1237 \livelink{chap:DWFORMsdata}{DW\-\_FORM\-\_sdata}&0x0d&constant \\
1238 \livelink{chap:DWFORMstrp}{DW\-\_FORM\-\_strp}&0x0e&string \\
1239 \livelink{chap:DWFORMudata}{DW\-\_FORM\-\_udata}&0x0f&constant \\
1240 \livelink{chap:DWFORMrefaddr}{DW\-\_FORM\-\_ref\-\_addr}&0x10&reference \\
1241 \livelink{chap:DWFORMref1}{DW\-\_FORM\-\_ref1}&0x11&reference \\
1242 \livelink{chap:DWFORMref2}{DW\-\_FORM\-\_ref2}&0x12&reference \\
1243 \livelink{chap:DWFORMref4}{DW\-\_FORM\-\_ref4}&0x13&reference \\
1244 \livelink{chap:DWFORMref8}{DW\-\_FORM\-\_ref8}&0x14&reference \\
1245 \livelink{chap:DWFORMrefudata}{DW\-\_FORM\-\_ref\-\_udata}&0x15&reference \\
1246 \livelink{chap:DWFORMindirect}{DW\-\_FORM\-\_indirect}&0x16&(see Section \refersec{datarep:abbreviationstables}) \\
1247 \livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset} \ddag &0x17&\livelink{chap:lineptr}{lineptr}, \livelink{chap:loclistptr}{loclistptr}, \livelink{chap:macptr}{macptr}, \livelink{chap:rangelistptr}{rangelistptr} \\
1248 \livelink{chap:DWFORMexprloc}{DW\-\_FORM\-\_exprloc} \ddag &0x18&\livelink{chap:exprloc}{exprloc} \\
1249 \livelink{chap:DWFORMflagpresent}{DW\-\_FORM\-\_flag\-\_present} \ddag &0x19&\livelink{chap:flag}{flag} \\
1250 \livelink{chap:DWFORMrefsig8}{DW\-\_FORM\-\_ref\-\_sig8} \ddag &0x20&reference \\
1257 \section{Variable Length Data}
1258 \label{datarep:variablelengthdata}
1259 \addtoindexx{variable length data|see {LEB128}}
1261 \addtoindexx{Little Endian Base 128|see{LEB128}}
1262 encoded using ``Little Endian Base 128''
1263 \addtoindexx{little-endian encoding|see{endian attribute}}
1265 \addtoindexx{LEB128}
1266 LEB128 is a scheme for encoding integers
1267 densely that exploits the assumption that most integers are
1270 \textit{This encoding is equally suitable whether the target machine
1271 architecture represents data in big\dash\ endian or little\dash endian
1272 order. It is ``little\dash endian'' only in the sense that it
1273 avoids using space to represent the ``big'' end of an
1274 unsigned integer, when the big end is all zeroes or sign
1277 Unsigned LEB128 (ULEB128) numbers are encoded as follows:
1278 \addtoindexx{LEB128!unsigned, encoding as}
1279 start at the low order end of an unsigned integer and chop
1280 it into 7\dash bit chunks. Place each chunk into the low order 7
1281 bits of a byte. Typically, several of the high order bytes
1282 will be zero; discard them. Emit the remaining bytes in a
1283 stream, starting with the low order byte; set the high order
1284 bit on each byte except the last emitted byte. The high bit
1285 of zero on the last byte indicates to the decoder that it
1286 has encountered the last byte.
1288 The integer zero is a special case, consisting of a single
1291 Table \refersec{tab:examplesofunsignedleb128encodings}
1292 gives some examples of unsigned LEB128 numbers. The
1293 0x80 in each case is the high order bit of the byte, indicating
1294 that an additional byte follows.
1297 The encoding for signed, two\textquoteright s complement LEB128 (SLEB128)
1298 \addtoindexx{LEB128!signed, encoding as}
1299 numbers is similar, except that the criterion for discarding
1300 high order bytes is not whether they are zero, but whether
1301 they consist entirely of sign extension bits. Consider the
1302 32\dash bit integer -2. The three high level bytes of the number
1303 are sign extension, thus LEB128 would represent it as a single
1304 byte containing the low order 7 bits, with the high order
1305 bit cleared to indicate the end of the byte stream. Note
1306 that there is nothing within the LEB128 representation that
1307 indicates whether an encoded number is signed or unsigned. The
1308 decoder must know what type of number to expect.
1309 Table \refersec{tab:examplesofunsignedleb128encodings}
1310 gives some examples of unsigned LEB128 numbers and
1311 Table \refersec{tab:examplesofsignedleb128encodings}
1312 gives some examples of signed LEB128
1315 \textit{Appendix \refersec{app:variablelengthdataencodingdecodinginformative}
1316 \addtoindexx{LEB128!examples}
1317 gives algorithms for encoding and decoding these forms.}
1321 \setlength{\extrarowheight}{0.1cm}
1322 \begin{longtable}{l|l|l}
1323 \caption{Examples of unsigned LEB128 encodings}
1324 \label{tab:examplesofunsignedleb128encodings}
1325 \addtoindexx{LEB128 encoding!examples} \\
1326 \hline \bfseries Number&\bfseries First byte &\bfseries Second byte \\ \hline
1328 \bfseries Number&\bfseries First Byte &\bfseries Second byte\\ \hline
1330 \hline \emph{Continued on next page}
1336 128& 0 + 0x80 & 1 \\
1337 129& 1 + 0x80 & 1 \\
1338 130& 2 + 0x80 & 1 \\
1339 12857& 57 + 0x80 & 100 \\
1346 \setlength{\extrarowheight}{0.1cm}
1347 \begin{longtable}{l|l|l}
1348 \caption{Examples of signed LEB128 encodings} \label{tab:examplesofsignedleb128encodings} \\
1349 \hline \bfseries Number&\bfseries First byte &\bfseries Second byte \\ \hline
1351 \bfseries Number&\bfseries First Byte &\bfseries Second byte\\ \hline
1353 \hline \emph{Continued on next page}
1359 127& 127 + 0x80 & 0 \\
1360 -127& 1 + 0x80 & 0x7f \\
1361 128& 0 + 0x80 & 1 \\
1362 -128& 0 + 0x80 & 0x7f \\
1363 129& 1 + 0x80 & 1 \\
1364 -129& -x7f + 0x80 & 0xtc \\
1371 \section{DWARF Expressions and Location Descriptions}
1372 \label{datarep:dwarfexpressionsandlocationdescriptions}
1373 \subsection{DWARF Expressions}
1374 \label{datarep:dwarfexpressions}
1377 \addtoindexx{DWARF Expression!operator encoding}
1378 DWARF expression is stored in a \nolink{block} of contiguous
1379 bytes. The bytes form a sequence of operations. Each operation
1380 is a 1\dash byte code that identifies that operation, followed by
1381 zero or more bytes of additional data. The encodings for the
1382 operations are described in
1383 Table \refersec{tab:dwarfoperationencodings}.
1386 \setlength{\extrarowheight}{0.1cm}
1387 \begin{longtable}{l|l|c|l}
1388 \caption{DWARF operation encodings} \label{tab:dwarfoperationencodings} \\
1389 \hline & &\bfseries No. of &\\
1390 \bfseries Operation&\bfseries Code &\bfseries Operands &\bfseries Notes\\ \hline
1392 & &\bfseries No. of &\\
1393 \bfseries Operation&\bfseries Code &\bfseries Operands &\bfseries Notes\\ \hline
1395 \hline \emph{Continued on next page}
1398 \ddag \ \textit{New in \addtoindex{DWARF Version 4}}
1401 \livelink{chap:DWOPaddr}{DW\-\_OP\-\_addr}&0x03&1 & constant address \\
1402 & & &(size target specific) \\
1404 \livelink{chap:DWOPderef}{DW\-\_OP\-\_deref}&0x06&0 & \\
1407 \livelink{chap:DWOPconst1u}{DW\-\_OP\-\_const1u}&0x08&1&1\dash byte constant \\
1408 \livelink{chap:DWOPconst1s}{DW\-\_OP\-\_const1s}&0x09&1&1\dash byte constant \\
1409 \livelink{chap:DWOPconst2u}{DW\-\_OP\-\_const2u}&0x0a&1&2\dash byte constant \\
1410 \livelink{chap:DWOPconst2s}{DW\-\_OP\-\_const2s}&0x0b&1&2\dash byte constant \\
1411 \livelink{chap:DWOPconst4u}{DW\-\_OP\-\_const4u}&0x0c&1&4\dash byte constant \\
1412 \livelink{chap:DWOPconst4s}{DW\-\_OP\-\_const4s}&0x0d&1&4\dash byte constant \\
1413 \livelink{chap:DWOPconst8u}{DW\-\_OP\-\_const8u}&0x0e&1&8\dash byte constant \\
1414 \livelink{chap:DWOPconst8s}{DW\-\_OP\-\_const8s}&0x0f&1&8\dash byte constant \\
1415 \livelink{chap:DWOPconstu}{DW\-\_OP\-\_constu}&0x10&1&ULEB128 constant \\
1416 \livelink{chap:DWOPconsts}{DW\-\_OP\-\_consts}&0x11&1&SLEB128 constant \\
1417 \livelink{chap:DWOPdup}{DW\-\_OP\-\_dup}&0x12&0 & \\
1418 \livelink{chap:DWOPdrop}{DW\-\_OP\-\_drop}&0x13&0 & \\
1419 \livelink{chap:DWOPover}{DW\-\_OP\-\_over}&0x14&0 & \\
1420 \livelink{chap:DWOPpick}{DW\-\_OP\-\_pick}&0x15&1&1\dash byte stack index \\
1421 \livelink{chap:DWOPswap}{DW\-\_OP\-\_swap}&0x16&0 & \\
1422 \livelink{chap:DWOProt}{DW\-\_OP\-\_rot}&0x17&0 & \\
1423 \livelink{chap:DWOPxderef}{DW\-\_OP\-\_xderef}&0x18&0 & \\
1424 \livelink{chap:DWOPabs}{DW\-\_OP\-\_abs}&0x19&0 & \\
1425 \livelink{chap:DWOPand}{DW\-\_OP\-\_and}&0x1a&0 & \\
1426 \livelink{chap:DWOPdiv}{DW\-\_OP\-\_div}&0x1b&0 & \\
1430 \livelink{chap:DWOPminus}{DW\-\_OP\-\_minus}&0x1c&0 & \\
1431 \livelink{chap:DWOPmod}{DW\-\_OP\-\_mod}&0x1d&0 & \\
1432 \livelink{chap:DWOPmul}{DW\-\_OP\-\_mul}&0x1e&0 & \\
1433 \livelink{chap:DWOPneg}{DW\-\_OP\-\_neg}&0x1f&0 & \\
1434 \livelink{chap:DWOPnot}{DW\-\_OP\-\_not}&0x20&0 & \\
1435 \livelink{chap:DWOPor}{DW\-\_OP\-\_or}&0x21&0 & \\
1436 \livelink{chap:DWOPplus}{DW\-\_OP\-\_plus}&0x22&0 & \\
1437 \livelink{chap:DWOPplusuconst}{DW\-\_OP\-\_plus\-\_uconst}&0x23&1&ULEB128 addend \\
1438 \livelink{chap:DWOPshl}{DW\-\_OP\-\_shl}&0x24&0 & \\
1439 \livelink{chap:DWOPshr}{DW\-\_OP\-\_shr}&0x25&0 & \\
1440 \livelink{chap:DWOPshra}{DW\-\_OP\-\_shra}&0x26&0 & \\
1441 \livelink{chap:DWOPxor}{DW\-\_OP\-\_xor}&0x27&0 & \\
1442 \livelink{chap:DWOPskip}{DW\-\_OP\-\_skip}&0x2f&1&signed 2\dash byte constant \\
1443 \livelink{chap:DWOPbra}{DW\-\_OP\-\_bra}&0x28&1 & signed 2\dash byte constant \\
1444 \livelink{chap:DWOPeq}{DW\-\_OP\-\_eq}&0x29&0 & \\
1445 \livelink{chap:DWOPge}{DW\-\_OP\-\_ge}&0x2a&0 & \\
1446 \livelink{chap:DWOPgt}{DW\-\_OP\-\_gt}&0x2b&0 & \\
1447 \livelink{chap:DWOPle}{DW\-\_OP\-\_le}&0x2c&0 & \\
1448 \livelink{chap:DWOPlt}{DW\-\_OP\-\_lt}&0x2d&0 & \\
1449 \livelink{chap:DWOPne}{DW\-\_OP\-\_ne}&0x2e&0 & \\ \hline
1453 \livelink{chap:DWOPlit0}{DW\-\_OP\-\_lit0}&0x30 & 0 & \\
1455 \livelink{chap:DWOPlit1}{DW\-\_OP\-\_lit1}&0x31 & 0& literals 0 .. 31 = \\
1456 \ldots & & &\hspace{0.5cm}(\livelink{chap:DWOPlit0}{DW\-\_OP\-\_lit0} + literal) \\
1457 \livelink{chap:DWOPlit31}{DW\-\_OP\-\_lit31}&0x4f & 0 & \\ \hline
1459 \livelink{chap:DWOPreg0}{DW\-\_OP\-\_reg0} & 0x50 & 0 & \\
1460 \livelink{chap:DWOPreg1}{DW\-\_OP\-\_reg1} & 0x51 & 0® 0 .. 31 = \\
1461 \ldots & & &\hspace{0.5cm}(\livelink{chap:DWOPreg0}{DW\-\_OP\-\_reg0} + regnum) \\
1462 \livelink{chap:DWOPreg31}{DW\-\_OP\-\_reg31} & 0x6f & 0 & \\ \hline
1464 \livelink{chap:DWOPbreg0}{DW\-\_OP\-\_breg0} & 0x70 &1 & SLEB128 offset \\
1465 \livelink{chap:DWOPbreg1}{DW\-\_OP\-\_breg1} & 0x71 & 1 &base register 0 .. 31 = \\
1466 ... & & &\hspace{0.5cm}(\livelink{chap:DWOPbreg0}{DW\-\_OP\-\_breg0} + regnum) \\
1467 \livelink{chap:DWOPbreg31}{DW\-\_OP\-\_breg31} & 0x8f & 1 & \\ \hline
1469 \livelink{chap:DWOPregx}{DW\-\_OP\-\_regx} & 0x90 &1&ULEB128 register \\
1470 \livelink{chap:DWOPfbreg}{DW\-\_OP\-\_fbreg} & 0x91&1&SLEB128 offset \\
1471 \livelink{chap:DWOPbregx}{DW\-\_OP\-\_bregx} & 0x92&2 &ULEB128 register followed \\
1472 & & & by SLEB128 offset \\
1473 \livelink{chap:DWOPpiece}{DW\-\_OP\-\_piece} & 0x93 &1& ULEB128 size of piece addressed \\
1474 \livelink{chap:DWOPderefsize}{DW\-\_OP\-\_deref\-\_size} & 0x94 &1& 1-byte size of data retrieved \\
1475 \livelink{chap:DWOPxderefsize}{DW\-\_OP\-\_xderef\-\_size} & 0x95&1&1-byte size of data retrieved \\
1476 \livelink{chap:DWOPnop}{DW\-\_OP\-\_nop} & 0x96 &0& \\
1479 \livelink{chap:DWOPpushobjectaddress}{DW\-\_OP\-\_push\-\_object\-\_address}&0x97&0 & \\
1480 \livelink{chap:DWOPcall2}{DW\-\_OP\-\_call2}&0x98&1& 2\dash byte offset of DIE \\
1481 \livelink{chap:DWOPcall4}{DW\-\_OP\-\_call4}&0x99&1& 4\dash byte offset of DIE \\
1482 \livelink{chap:DWOPcallref}{DW\-\_OP\-\_call\-\_ref}&0x9a&1& 4\dash\ or 8\dash byte\\
1483 &&& offset of DIE \\
1484 \livelink{chap:DWOPformtlsaddress}{DW\-\_OP\-\_form\-\_tls\-\_address}&0x9b &0& \\
1485 \livelink{chap:DWOPcallframecfa}{DW\-\_OP\-\_call\-\_frame\-\_cfa} &0x9c &0& \\
1486 \livelink{chap:DWOPbitpiece}{DW\-\_OP\-\_bit\-\_piece}&0x9d &2&ULEB128 size followed by \\
1488 \livelink{chap:DWOPimplicitvalue}{DW\-\_OP\-\_implicit\-\_value} \ddag &0x9e &2&ULEB128 size followed by \\
1489 &&&\nolink{block} of that size\\
1490 \livelink{chap:DWOPstackvalue}{DW\-\_OP\-\_stack\-\_value} \ddag &0x9f &0& \\
1491 \livetarg{chap:DWOPlouser}{DW\-\_OP\-\_lo\-\_user} &0xe0 && \\
1492 \livetarg{chap:DWOPhiuser}{DW\-\_OP\-\_hi\-\_user} &0xff && \\
1498 \subsection{Location Descriptions}
1499 \label{datarep:locationdescriptions}
1501 A location description is used to compute the
1502 location of a variable or other entity.
1504 \subsection{Location Lists}
1505 \label{datarep:locationlists}
1507 Each entry in a \addtoindex{location list} is either a location list entry,
1508 a base address selection entry, or an
1509 \addtoindex{end of list entry!in location list}
1512 A \addtoindex{location list} entry consists of two address offsets followed
1513 by a 2\dash byte length, followed by a block of contiguous bytes
1514 that contains a DWARF location description. The length
1515 specifies the number of bytes in that block. The two offsets
1516 are the same size as an address on the target machine.
1518 A base address selection entry and an
1519 \addtoindex{end of list entry!in location list}
1520 end of list entry each
1521 consist of two (constant or relocated) address offsets. The two
1522 offsets are the same size as an address on the target machine.
1524 For a \addtoindex{location list} to be specified, the base address of
1525 \addtoindexx{base address selection entry!in location list}
1526 the corresponding compilation unit must be defined
1527 (see Section \refersec{chap:normalandpartialcompilationunitentries}).
1529 \section{Base Type Attribute Encodings}
1530 \label{datarep:basetypeattributeencodings}
1532 The encodings of the
1533 \hypertarget{chap:DWATencodingencodingofbasetype}
1535 \addtoindexx{encoding attribute!encoding}
1537 \livelink{chap:DWATencoding}{DW\-\_AT\-\_encoding}
1538 attribute are given in
1539 Table \refersec{tab:basetypeencodingvalues}
1542 \setlength{\extrarowheight}{0.1cm}
1543 \begin{longtable}{l|c}
1544 \caption{Base type encoding values} \label{tab:basetypeencodingvalues} \\
1545 \hline \bfseries Base type encoding code name&\bfseries Value \\ \hline
1547 \bfseries Base type encoding code name&\bfseries Value\\ \hline
1549 \hline \emph{Continued on next page}
1552 \ddag \ \textit{New in \addtoindex{DWARF Version 4}}
1555 \livelink{chap:DWATEaddress}{DW\-\_ATE\-\_address}&0x01 \\
1556 \livelink{chap:DWATEboolean}{DW\-\_ATE\-\_boolean}&0x02 \\
1557 \livelink{chap:DWATEcomplexfloat}{DW\-\_ATE\-\_complex\-\_float}&0x03 \\
1558 \livelink{chap:DWATEfloat}{DW\-\_ATE\-\_float}&0x04 \\
1559 \livelink{chap:DWATEsigned}{DW\-\_ATE\-\_signed}&0x05 \\
1560 \livelink{chap:DWATEsignedchar}{DW\-\_ATE\-\_signed\-\_char}&0x06 \\
1561 \livelink{chap:DWATEunsigned}{DW\-\_ATE\-\_unsigned}&0x07 \\
1562 \livelink{chap:DWATEunsignedchar}{DW\-\_ATE\-\_unsigned\-\_char}&0x08 \\
1563 \livelink{chap:DWATEimaginaryfloat}{DW\-\_ATE\-\_imaginary\-\_float}&0x09 \\
1564 \livelink{chap:DWATEpackeddecimal}{DW\-\_ATE\-\_packed\-\_decimal}&0x0a \\
1565 \livelink{chap:DWATEnumericstring}{DW\-\_ATE\-\_numeric\-\_string}&0x0b \\
1566 \livelink{chap:DWATEedited}{DW\-\_ATE\-\_edited}&0x0c \\
1567 \livelink{chap:DWATEsignedfixed}{DW\-\_ATE\-\_signed\-\_fixed}&0x0d \\
1568 \livelink{chap:DWATEunsignedfixed}{DW\-\_ATE\-\_unsigned\-\_fixed}&0x0e \\
1569 \livelink{chap:DWATEdecimalfloat}{DW\-\_ATE\-\_decimal\-\_float} & 0x0f \\
1570 \livelink{chap:DWATEUTF}{DW\-\_ATE\-\_UTF} \ddag & 0x10 \\
1571 \livetarg{chap:DWATElouser}{DW\-\_ATE\-\_lo\-\_user} & 0x80 \\
1572 \livetarg{chap:DWATEhiuser}{DW\-\_ATE\-\_hi\-\_user} & 0xff \\
1578 The encodings of the constants used in the
1579 \livelink{chap:DWATdecimalsign}{DW\-\_AT\-\_decimal\-\_sign} attribute
1581 Table \refersec{tab:decimalsignencodings}.
1585 \setlength{\extrarowheight}{0.1cm}
1586 \begin{longtable}{l|c}
1587 \caption{Decimal sign encodings} \label{tab:decimalsignencodings} \\
1588 \hline \bfseries Decimal sign code name&\bfseries Value \\ \hline
1590 \bfseries Decimal sign code name&\bfseries Value\\ \hline
1592 \hline \emph{Continued on next page}
1597 \livelink{chap:DWDSunsigned}{DW\-\_DS\-\_unsigned} & 0x01 \\
1598 \livelink{chap:DWDSleadingoverpunch}{DW\-\_DS\-\_leading\-\_overpunch} & 0x02 \\
1599 \livelink{chap:DWDStrailingoverpunch}{DW\-\_DS\-\_trailing\-\_overpunch} & 0x03 \\
1600 \livelink{chap:DWDSleadingseparate}{DW\-\_DS\-\_leading\-\_separate} & 0x04 \\
1601 \livelink{chap:DWDStrailingseparate}{DW\-\_DS\-\_trailing\-\_separate} & 0x05 \\
1606 The encodings of the constants used in the
1607 \livelink{chap:DWATendianity}{DW\-\_AT\-\_endianity} attribute are given in
1608 Table \refersec{tab:endianityencodings}.
1611 \setlength{\extrarowheight}{0.1cm}
1612 \begin{longtable}{l|c}
1613 \caption{Endianity encodings} \label{tab:endianityencodings}\\
1614 \hline \bfseries Endian code name&\bfseries Value \\ \hline
1616 \bfseries Endian code name&\bfseries Value\\ \hline
1618 \hline \emph{Continued on next page}
1623 \livelink{chap:DWENDdefault}{DW\-\_END\-\_default} & 0x00 \\
1624 \livelink{chap:DWENDbig}{DW\-\_END\-\_big} & 0x01 \\
1625 \livelink{chap:DWENDlittle}{DW\-\_END\-\_little} & 0x02 \\
1626 \livetarg{chap:DWENDlouser}{DW\-\_END\-\_lo\-\_user} & 0x40 \\
1627 \livetarg{chap:DWENDhiuser}{DW\-\_END\-\_hi\-\_user} & 0xff \\
1632 \section{Accessibility Codes}
1633 \label{datarep:accessibilitycodes}
1634 The encodings of the constants used in the
1635 \livelink{chap:DWATaccessibility}{DW\-\_AT\-\_accessibility}
1637 \addtoindexx{accessibility attribute!encoding}
1639 Table \refersec{tab:accessibilityencodings}.
1642 \setlength{\extrarowheight}{0.1cm}
1643 \begin{longtable}{l|c}
1644 \caption{Accessibility encodings} \label{tab:accessibilityencodings}\\
1645 \hline \bfseries Accessibility code name&\bfseries Value \\ \hline
1647 \bfseries Accessibility code name&\bfseries Value\\ \hline
1649 \hline \emph{Continued on next page}
1654 \livelink{chap:DWACCESSpublic}{DW\-\_ACCESS\-\_public}&0x01 \\
1655 \livelink{chap:DWACCESSprotected}{DW\-\_ACCESS\-\_protected}&0x02 \\
1656 \livelink{chap:DWACCESSprivate}{DW\-\_ACCESS\-\_private}&0x03 \\
1662 \section{Visibility Codes}
1663 \label{datarep:visibilitycodes}
1664 The encodings of the constants used in the
1665 \livelink{chap:DWATvisibility}{DW\-\_AT\-\_visibility} attribute are given in
1666 Table \refersec{tab:visibilityencodings}.
1669 \setlength{\extrarowheight}{0.1cm}
1670 \begin{longtable}{l|c}
1671 \caption{Visibility encodings} \label{tab:visibilityencodings}\\
1672 \hline \bfseries Visiibility code name&\bfseries Value \\ \hline
1674 \bfseries Visibility code name&\bfseries Value\\ \hline
1676 \hline \emph{Continued on next page}
1681 \livelink{chap:DWVISlocal}{DW\-\_VIS\-\_local}&0x01 \\
1682 \livelink{chap:DWVISexported}{DW\-\_VIS\-\_exported}&0x02 \\
1683 \livelink{chap:DWVISqualified}{DW\-\_VIS\-\_qualified}&0x03 \\
1688 \section{Virtuality Codes}
1689 \label{datarep:vitualitycodes}
1691 The encodings of the constants used in the
1692 \livelink{chap:DWATvirtuality}{DW\-\_AT\-\_virtuality} attribute are given in
1693 Table \refersec{tab:virtualityencodings}.
1696 \setlength{\extrarowheight}{0.1cm}
1697 \begin{longtable}{l|c}
1698 \caption{Virtuality encodings} \label{tab:virtualityencodings}\\
1699 \hline \bfseries Virtuality code name&\bfseries Value \\ \hline
1701 \bfseries Virtuality code name&\bfseries Value\\ \hline
1703 \hline \emph{Continued on next page}
1708 \livelink{chap:DWVIRTUALITYnone}{DW\-\_VIRTUALITY\-\_none}&0x00 \\
1709 \livelink{chap:DWVIRTUALITYvirtual}{DW\-\_VIRTUALITY\-\_virtual}&0x01 \\
1710 \livelink{chap:DWVIRTUALITYpurevirtual}{DW\-\_VIRTUALITY\-\_pure\-\_virtual}&0x02 \\
1718 \livelink{chap:DWVIRTUALITYnone}{DW\-\_VIRTUALITY\-\_none} is equivalent to the absence of the
1719 \livelink{chap:DWATvirtuality}{DW\-\_AT\-\_virtuality}
1722 \section{Source Languages}
1723 \label{datarep:sourcelanguages}
1725 The encodings of the constants used
1726 \addtoindexx{language attribute, encoding}
1728 \addtoindexx{language name encoding}
1730 \livelink{chap:DWATlanguage}{DW\-\_AT\-\_language}
1731 attribute are given in
1732 Table \refersec{tab:languageencodings}.
1734 % If we don't force a following space it looks odd
1736 and their associated values are reserved, but the
1737 languages they represent are not well supported.
1738 Table \refersec{tab:languageencodings}
1740 \addtoindexx{lower bound attribute!default}
1741 default lower bound, if any, assumed for
1742 an omitted \livelink{chap:DWATlowerbound}{DW\-\_AT\-\_lower\-\_bound} attribute in the context of a
1743 \livelink{chap:DWTAGsubrangetype}{DW\-\_TAG\-\_subrange\-\_type} debugging information entry for each
1747 \setlength{\extrarowheight}{0.1cm}
1748 \begin{longtable}{l|c|c}
1749 \caption{Language encodings} \label{tab:languageencodings}\\
1750 \hline \bfseries Language name&\bfseries Value &\bfseries Default Lower Bound \\ \hline
1752 \bfseries Language name&\bfseries Value &\bfseries Default Lower Bound\\ \hline
1754 \hline \emph{Continued on next page}
1757 \dag \ \textit{See text}
1760 \livelink{chap:DWLANGC89}{DW\-\_LANG\-\_C89}&0x0001&0 \\
1761 \livelink{chap:DWLANGC}{DW\-\_LANG\-\_C}&0x0002&0 \\
1762 \livelink{chap:DWLANGAda83}{DW\-\_LANG\-\_Ada83} \dag &0x0003&1 \addtoindexx{Ada} \\
1763 \livelink{chap:DWLANGCplusplus}{DW\-\_LANG\-\_C\-\_plus\-\_plus} &0x0004&0 \\
1764 \livelink{chap:DWLANGCobol74}{DW\-\_LANG\-\_Cobol74} \dag &0x0005&1 \\
1765 \livelink{chap:DWLANGCobol85}{DW\-\_LANG\-\_Cobol85} \dag &0x0006&1 \\
1766 \livelink{chap:DWLANGFortran77}{DW\-\_LANG\-\_Fortran77}&0x0007&1 \\
1767 \livelink{chap:DWLANGFortran90}{DW\-\_LANG\-\_Fortran90}&0x0008&1 \\
1768 \livelink{chap:DWLANGPascal83}{DW\-\_LANG\-\_Pascal83}&0x0009&1 \\
1769 \livelink{chap:DWLANGModula2}{DW\-\_LANG\-\_Modula2}&0x000a&1 \\
1770 \livelink{chap:DWLANGJava}{DW\-\_LANG\-\_Java}&0x000b&0 \\
1771 \livelink{chap:DWLANGC99}{DW\-\_LANG\-\_C99}&0x000c&0 \\
1772 \livelink{chap:DWLANGAda95}{DW\-\_LANG\-\_Ada95} \dag &0x000d&1 \addtoindexx{Ada} \\
1773 \livelink{chap:DWLANGFortran95}{DW\-\_LANG\-\_Fortran95} &0x000e&1 \\
1774 \livelink{chap:DWLANGPLI}{DW\-\_LANG\-\_PLI} \dag &0x000f&1 \\
1775 \livelink{chap:DWLANGObjC}{DW\-\_LANG\-\_ObjC}&0x0010&0 \\
1776 \livelink{chap:DWLANGObjCplusplus}{DW\-\_LANG\-\_ObjC\-\_plus\-\_plus}&0x0011&0 \\
1777 \livelink{chap:DWLANGUPC}{DW\-\_LANG\-\_UPC}&0x0012&0 \\
1778 \livelink{chap:DWLANGD}{DW\-\_LANG\-\_D}&0x0013&0 \\
1779 \livelink{chap:DWLANGPython}{DW\-\_LANG\-\_Python} \dag &0x0014&0 \\
1780 \livetarg{chap:DWLANGlouser}{DW\-\_LANG\-\_lo\-\_user}&0x8000 & \\
1781 \livetarg{chap:DWLANGhiuser}{DW\-\_LANG\-\_hi\-\_user}&0xffff & \\
1786 \section{Address Class Encodings}
1787 \label{datarep:addressclassencodings}
1789 The value of the common
1790 \addtoindexi{address}{address class!attribute encoding}
1792 \livelink{chap:DWADDRnone}{DW\-\_ADDR\-\_none} is 0.
1795 \section{Identifier Case}
1796 \label{datarep:identifiercase}
1798 The encodings of the constants used in the
1799 \livelink{chap:DWATidentifiercase}{DW\-\_AT\-\_identifier\-\_case} attribute are given in
1800 Table \refersec{tab:identifiercaseencodings}.
1803 \setlength{\extrarowheight}{0.1cm}
1804 \begin{longtable}{l|c}
1805 \caption{Identifier case encodings} \label{tab:identifiercaseencodings}\\
1806 \hline \bfseries Identifier case name&\bfseries Value \\ \hline
1808 \bfseries Identifier case name&\bfseries Value\\ \hline
1810 \hline \emph{Continued on next page}
1814 \livelink{chap:DWIDcasesensitive}{DW\-\_ID\-\_case\-\_sensitive}&0x00 \\
1815 \livelink{chap:DWIDupcase}{DW\-\_ID\-\_up\-\_case}&0x01 \\
1816 \livelink{chap:DWIDdowncase}{DW\-\_ID\-\_down\-\_case}&0x02 \\
1817 \livelink{chap:DWIDcaseinsensitive}{DW\-\_ID\-\_case\-\_insensitive}&0x03 \\
1821 \section{Calling Convention Encodings}
1822 \label{datarep:callingconventionencodings}
1823 The encodings of the constants used in the
1824 \livelink{chap:DWATcallingconvention}{DW\-\_AT\-\_calling\-\_convention} attribute are given in
1825 Table \refersec{tab:callingconventionencodings}.
1828 \setlength{\extrarowheight}{0.1cm}
1829 \begin{longtable}{l|c}
1830 \caption{Calling convention encodings} \label{tab:callingconventionencodings}\\
1831 \hline \bfseries Calling Convention name&\bfseries Value \\ \hline
1833 \bfseries Calling Convention name&\bfseries Value\\ \hline
1835 \hline \emph{Continued on next page}
1840 \livelink{chap:DWCCnormal}{DW\-\_CC\-\_normal}&0x01 \\
1841 \livelink{chap:DWCCprogram}{DW\-\_CC\-\_program}&0x02 \\
1842 \livelink{chap:DWCCnocall}{DW\-\_CC\-\_nocall}&0x03 \\
1843 \livetarg{chap:DWCClouser}{DW\-\_CC\-\_lo\-\_user}&0x40 \\
1844 \livetarg{chap:DWCChiuser}{DW\-\_CC\-\_hi\-\_user}&0xff \\
1849 \section{Inline Codes}
1850 \label{datarep:inlinecodes}
1852 The encodings of the constants used in
1853 \addtoindexx{inline attribute!encoding}
1855 \livelink{chap:DWATinline}{DW\-\_AT\-\_inline} attribute are given in
1856 Table \refersec{tab:inlineencodings}.
1860 \setlength{\extrarowheight}{0.1cm}
1861 \begin{longtable}{l|c}
1862 \caption{Inline encodings} \label{tab:inlineencodings}\\
1863 \hline \bfseries Inline Code name&\bfseries Value \\ \hline
1865 \bfseries Inline Code name&\bfseries Value\\ \hline
1867 \hline \emph{Continued on next page}
1872 \livelink{chap:DWINLnotinlined}{DW\-\_INL\-\_not\-\_inlined}&0x00 \\
1873 \livelink{chap:DWINLinlined}{DW\-\_INL\-\_inlined}&0x01 \\
1874 \livelink{chap:DWINLdeclarednotinlined}{DW\-\_INL\-\_declared\-\_not\-\_inlined}&0x02 \\
1875 \livelink{chap:DWINLdeclaredinlined}{DW\-\_INL\-\_declared\-\_inlined}&0x03 \\
1880 % this clearpage is ugly, but the following table came
1881 % out oddly without it.
1883 \section{Array Ordering}
1884 \label{datarep:arrayordering}
1886 The encodings of the constants used in the
1887 \livelink{chap:DWATordering}{DW\-\_AT\-\_ordering} attribute are given in
1888 Table \refersec{tab:orderingencodings}.
1891 \setlength{\extrarowheight}{0.1cm}
1892 \begin{longtable}{l|c}
1893 \caption{Ordering encodings} \label{tab:orderingencodings}\\
1894 \hline \bfseries Ordering name&\bfseries Value \\ \hline
1896 \bfseries Ordering name&\bfseries Value\\ \hline
1898 \hline \emph{Continued on next page}
1903 \livelink{chap:DWORDrowmajor}{DW\-\_ORD\-\_row\-\_major}&0x00 \\
1904 \livelink{chap:DWORDcolmajor}{DW\-\_ORD\-\_col\-\_major}&0x01 \\
1910 \section{Discriminant Lists}
1911 \label{datarep:discriminantlists}
1913 The descriptors used in
1914 \addtoindexx{discriminant list attribute!encoding}
1916 \livelink{chap:DWATdiscrlist}{DW\-\_AT\-\_discr\-\_list} attribute are
1917 encoded as 1\dash byte constants. The
1918 defined values are given in
1919 Table \refersec{tab:discriminantdescriptorencodings}.
1921 % Odd that the 'Name' field capitalized here, it is not caps elsewhere.
1923 \setlength{\extrarowheight}{0.1cm}
1924 \begin{longtable}{l|c}
1925 \caption{Discriminant descriptor encodings} \label{tab:discriminantdescriptorencodings}\\
1926 \hline \bfseries Descriptor Name&\bfseries Value \\ \hline
1928 \bfseries Descriptor Name&\bfseries Value\\ \hline
1930 \hline \emph{Continued on next page}
1935 \livetarg{chap:DWDSClabel}{DW\-\_DSC\-\_label}&0x00 \\
1936 \livetarg{chap:DWDSCrange}{DW\-\_DSC\-\_range}&0x01 \\
1942 \section{Name Lookup Tables}
1943 \label{datarep:namelookuptables}
1945 Each set of entries in the table of global names contained
1946 in the \addtoindex{.debug\_pubnames} and
1947 \addtoindex{.debug\_pubtypes} sections begins
1948 with a header consisting of:
1951 \begin{enumerate}[1.]
1952 \item unit\_length (initial length) \\
1953 \addtoindexx{unit\_length}
1954 A 4\dash byte or 12\dash byte unsigned integer
1955 \addtoindexx{initial length}
1956 representing the length
1957 of the \addtoindex{.debug\_info}
1958 contribution for that compilation unit,
1959 not including the length field itself. In the 32\dash bit DWARF
1960 format, this is a 4\dash byte unsigned integer (which must be less
1961 than 0xfffffff0); in the 64\dash bit DWARF format, this consists
1962 of the 4\dash byte value 0xffffffff followed by an 8\dash byte unsigned
1963 integer that gives the actual length
1964 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
1966 \item version (\addtoindex{uhalf})
1967 A 2\dash byte unsigned integer representing the version of the
1968 DWARF information\addtoindexx{version number!compilation unit} for the compilation unit
1969 \addtoindexx{version number!name lookup table}
1970 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
1971 The value in this field is 4.
1973 % Some say unsigned offset this just says offset: FIXME
1974 \item \addtoindex{debug\_info\_offset} (section offset) \\
1976 \addtoindexx{section offset!in name lookup table set of entries}
1977 4\dash byte or 8\dash byte
1979 \addtoindex{.debug\_info}
1980 section of the compilation unit header.
1982 the 32\dash bit DWARF format, this is a 4\dash byte unsigned offset;
1983 in the 64\dash bit DWARF format, this is an 8\dash byte unsigned offsets
1984 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
1986 \item \addtoindex{debug\_info\_length} (section length) \\
1987 \addtoindexx{section length!in .debug\_pubnames header}
1989 \addtoindexx{section length!in .debug\_pubtypes header}
1990 4\dash byte or 8\dash byte length containing the size in bytes of the
1991 contents of the \addtoindex{.debug\_info}
1992 section generated to represent
1993 this compilation unit. In the 32\dash bit DWARF format, this is
1994 a 4\dash byte unsigned length; in the 64\dash bit DWARF format, this
1995 is an 8-byte unsigned length
1996 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
2001 This header is followed by a series of tuples. Each tuple
2002 consists of a 4\dash byte or 8\dash byte offset followed by a string
2003 of non\dash null bytes terminated by one null byte.
2005 DWARF format, this is a 4\dash byte offset; in the 64\dash bit DWARF
2006 format, it is an 8\dash byte offset.
2007 Each set is terminated by an
2008 offset containing the value 0.
2012 \section{Address Range Table}
2013 \label{datarep:addrssrangetable}
2015 Each set of entries in the table of address ranges contained
2016 in the \addtoindex{.debug\_aranges}
2017 section begins with a header containing:
2019 \begin{enumerate}[1.]
2020 % FIXME The unit length text is not fully consistent across
2023 \item unit\_length (initial length) \\
2024 \addtoindexx{unit\_length}
2025 A 4-byte or 12-byte length containing the length of the
2026 \addtoindexx{initial length}
2027 set of entries for this compilation unit, not including the
2028 length field itself. In the 32-bit DWARF format, this is a
2029 4-byte unsigned integer (which must be less than 0xfffffff0);
2030 in the 64-bit DWARF format, this consists of the 4-byte value
2031 0xffffffff followed by an 8-byte unsigned integer that gives
2033 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
2035 \item version (\addtoindex{uhalf}) \\
2036 A 2\dash byte version identifier
2037 \addtoindexx{version number!address range table} containing the value 2
2038 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
2040 \item debug\_info\_offset (section offset) \\
2042 \addtoindexx{section offset!in .debug\_aranges header}
2043 4\dash byte or 8\dash byte offset into the
2044 \addtoindex{.debug\_info} section of
2045 the compilation unit header. In the 32\dash bit DWARF format,
2046 this is a 4\dash byte unsigned offset; in the 64\dash bit DWARF format,
2047 this is an 8\dash byte unsigned offset
2048 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
2050 \item address\_size (ubyte) \\
2051 A 1\dash byte unsigned integer containing the size in bytes of an
2052 \addtoindexx{address\_size}
2054 \addtoindexx{size of an address}
2055 (or the offset portion of an address for segmented
2056 \addtoindexx{address space!segmented}
2057 addressing) on the target system.
2059 \item segment\_size (ubyte) \\
2061 \addtoindexx{segment\_size}
2062 1\dash byte unsigned integer containing the size in bytes of a
2063 segment selector on the target system.
2067 This header is followed by a series of tuples. Each tuple
2068 consists of a segment, an address and a length.
2070 size is given by the \addtoindex{segment\_size} field of the header; the
2071 address and length size are each given by the address\_size
2072 field of the header.
2073 The first tuple following the header in
2074 each set begins at an offset that is a multiple of the size
2075 of a single tuple (that is, the size of a segment selector
2076 plus twice the \addtoindex{size of an address}).
2077 The header is padded, if
2078 necessary, to that boundary. Each set of tuples is terminated
2079 by a 0 for the segment, a 0 for the address and 0 for the
2080 length. If the \addtoindex{segment\_size} field in the header is zero,
2081 the segment selectors are omitted from all tuples, including
2082 the terminating tuple.
2085 \section{Line Number Information}
2086 \label{datarep:linenumberinformation}
2088 The \addtoindexi{version number}{version number!line number information}
2089 in the line number program header is 4
2090 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
2092 The boolean values ``true'' and ``false''
2093 used by the line number information program are encoded
2094 as a single byte containing the value 0
2095 for ``false,'' and a non-zero value for ``true.''
2097 The encodings for the standard opcodes are given in
2098 \addtoindexx{line number opcodes!standard opcode encoding}
2099 Table \refersec{tab:linenumberstandardopcodeencodings}.
2101 % Odd that the 'Name' field capitalized here, it is not caps elsewhere.
2103 \setlength{\extrarowheight}{0.1cm}
2104 \begin{longtable}{l|c}
2105 \caption{Line Number Standard Opcode encodings} \label{tab:linenumberstandardopcodeencodings}\\
2106 \hline \bfseries Opcode Name&\bfseries Value \\ \hline
2108 \bfseries Opcode Name&\bfseries Value\\ \hline
2110 \hline \emph{Continued on next page}
2115 \livelink{chap:DWLNScopy}{DW\-\_LNS\-\_copy}&0x01 \\
2116 \livelink{chap:DWLNSadvancepc}{DW\-\_LNS\-\_advance\-\_pc}&0x02 \\
2117 \livelink{chap:DWLNSadvanceline}{DW\-\_LNS\-\_advance\-\_line}&0x03 \\
2118 \livelink{chap:DWLNSsetfile}{DW\-\_LNS\-\_set\-\_file}&0x04 \\
2119 \livelink{chap:DWLNSsetcolumn}{DW\-\_LNS\-\_set\-\_column}&0x05 \\
2120 \livelink{chap:DWLNSnegatestmt}{DW\-\_LNS\-\_negate\-\_stmt}&0x06 \\
2121 \livelink{chap:DWLNSsetbasicblock}{DW\-\_LNS\-\_set\-\_basic\-\_block}&0x07 \\
2122 \livelink{chap:DWLNSconstaddpc}{DW\-\_LNS\-\_const\-\_add\-\_pc}&0x08 \\
2123 \livelink{chap:DWLNSfixedadvancepc}{DW\-\_LNS\-\_fixed\-\_advance\-\_pc}&0x09 \\
2124 \livelink{chap:DWLNSsetprologueend}{DW\-\_LNS\-\_set\-\_prologue\-\_end}&0x0a \\
2125 \livelink{chap:DWLNSsetepiloguebegin}{DW\-\_LNS\-\_set\-\_epilogue\-\_begin}&0x0b \\
2126 \livelink{chap:DWLNSsetisa}{DW\-\_LNS\-\_set\-\_isa}&0x0c \\
2133 The encodings for the extended opcodes are given in
2134 \addtoindexx{line number opcodes!extended opcode encoding}
2135 Table \refersec{tab:linenumberextendedopcodeencodings}.
2138 \setlength{\extrarowheight}{0.1cm}
2139 \begin{longtable}{l|c}
2140 \caption{Line Number Extended Opcode encodings} \label{tab:linenumberextendedopcodeencodings}\\
2141 \hline \bfseries Opcode Name&\bfseries Value \\ \hline
2143 \bfseries Opcode Name&\bfseries Value\\ \hline
2145 \hline \emph{Continued on next page}
2148 \ddag \ \textit{New in \addtoindex{DWARF Version 4}}
2151 \livelink{chap:DWLNEendsequence}{DW\-\_LNE\-\_end\-\_sequence}&0x01 \\
2152 \livelink{chap:DWLNEsetaddress}{DW\-\_LNE\-\_set\-\_address}&0x02\\
2153 \livelink{chap:DWLNEdefinefile}{DW\-\_LNE\-\_define\-\_file}&0x03\\
2154 \livelink{chap:DWLNEsetdiscriminator}{DW\-\_LNE\-\_set\-\_discriminator} \ddag &0x04 \\
2155 \livetarg{chap:DWLNElouser}{DW\-\_LNE\-\_lo\-\_user}&0x80 \\
2156 \livetarg{chap:DWLNEhiuser}{DW\-\_LNE\-\_hi\-\_user}&0xff \\
2161 \section{Macro Information}
2162 \label{datarep:macroinformation}
2164 The source line numbers and source file indices encoded in the
2165 macro information section are represented as unsigned LEB128
2166 numbers as are the constants in a
2167 \livelink{chap:DWMACINFOvendorext}{DW\-\_MACINFO\-\_vendor\-\_ext} entry.
2169 The macinfo type is encoded as a single byte.
2171 \addtoindexx{macinfo types!encoding}
2173 Table \refersec{tab:macinfotypeencodings}.
2177 \setlength{\extrarowheight}{0.1cm}
2178 \begin{longtable}{l|c}
2179 \caption{Macinfo Type Encodings} \label{tab:macinfotypeencodings}\\
2180 \hline \bfseries Macinfo Type Name&\bfseries Value \\ \hline
2182 \bfseries Macinfo Type Name&\bfseries Value\\ \hline
2184 \hline \emph{Continued on next page}
2189 \livelink{chap:DWMACINFOdefine}{DW\-\_MACINFO\-\_define}&0x01 \\
2190 \livelink{chap:DWMACINFOundef}{DW\-\_MACINFO\-\_undef}&0x02 \\
2191 \livelink{chap:DWMACINFOstartfile}{DW\-\_MACINFO\-\_start\-\_file}&0x03 \\
2192 \livelink{chap:DWMACINFOendfile}{DW\-\_MACINFO\-\_end\-\_file}&0x04 \\
2193 \livelink{chap:DWMACINFOvendorext}{DW\-\_MACINFO\-\_vendor\-\_ext}&0xff \\
2199 \section{Call Frame Information}
2200 \label{datarep:callframeinformation}
2202 In the 32\dash bit DWARF format, the value of the CIE id in the
2203 CIE header is 0xffffffff; in the 64\dash bit DWARF format, the
2204 value is 0xffffffffffffffff.
2206 The value of the CIE \addtoindexi{version number}{version number!call frame information}
2207 is 4 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
2209 Call frame instructions are encoded in one or more bytes. The
2210 primary opcode is encoded in the high order two bits of
2211 the first byte (that is, opcode = byte >> 6). An operand
2212 or extended opcode may be encoded in the low order 6
2213 bits. Additional operands are encoded in subsequent bytes.
2214 The instructions and their encodings are presented in
2215 Table \refersec{tab:callframeinstructionencodings}.
2218 \setlength{\extrarowheight}{0.1cm}
2219 \begin{longtable}{l|c|c|l|l}
2220 \caption{Call frame instruction encodings} \label{tab:callframeinstructionencodings} \\
2221 \hline &\bfseries High 2 &\bfseries Low 6 & & \\
2222 \bfseries Instruction&\bfseries Bits &\bfseries Bits &\bfseries Operand 1 &\bfseries Operand 2\\ \hline
2224 & \bfseries High 2 &\bfseries Low 6 & &\\
2225 \bfseries Instruction&\bfseries Bits &\bfseries Bits &\bfseries Operand 1 &\bfseries Operand 2\\ \hline
2227 \hline \emph{Continued on next page}
2232 \livelink{chap:DWCFAadvanceloc}{DW\-\_CFA\-\_advance\-\_loc}&0x1&delta & \\
2233 \livelink{chap:DWCFAoffset}{DW\-\_CFA\-\_offset}&0x2®ister&ULEB128 offset \\
2234 \livelink{chap:DWCFArestore}{DW\-\_CFA\-\_restore}&0x3®ister & & \\
2235 \livelink{chap:DWCFAnop}{DW\-\_CFA\-\_nop}&0&0 & & \\
2236 \livelink{chap:DWCFAsetloc}{DW\-\_CFA\-\_set\-\_loc}&0&0x01&address & \\
2237 \livelink{chap:DWCFAadvanceloc1}{DW\-\_CFA\-\_advance\-\_loc1}&0&0x02&1\dash byte delta & \\
2238 \livelink{chap:DWCFAadvanceloc2}{DW\-\_CFA\-\_advance\-\_loc2}&0&0x03&2\dash byte delta & \\
2239 \livelink{chap:DWCFAadvanceloc4}{DW\-\_CFA\-\_advance\-\_loc4}&0&0x04&4\dash byte delta & \\
2240 \livelink{chap:DWCFAoffsetextended}{DW\-\_CFA\-\_offset\-\_extended}&0&0x05&ULEB128 register&ULEB128 offset \\
2241 \livelink{chap:DWCFArestoreextended}{DW\-\_CFA\-\_restore\-\_extended}&0&0x06&ULEB128 register & \\
2242 \livelink{chap:DWCFAundefined}{DW\-\_CFA\-\_undefined}&0&0x07&ULEB128 register & \\
2243 \livelink{chap:DWCFAsamevalue}{DW\-\_CFA\-\_same\-\_value}&0&0x08 &ULEB128 register & \\
2244 \livelink{chap:DWCFAregister}{DW\-\_CFA\-\_register}&0&0x09&ULEB128 register &ULEB128 offset \\
2245 \livelink{chap:DWCFArememberstate}{DW\-\_CFA\-\_remember\-\_state}&0&0x0a & & \\
2246 \livelink{chap:DWCFArestorestate}{DW\-\_CFA\-\_restore\-\_state}&0&0x0b & & \\
2247 \livelink{chap:DWCFAdefcfa}{DW\-\_CFA\-\_def\-\_cfa}&0&0x0c &ULEB128 register&ULEB128 offset \\
2248 \livelink{chap:DWCFAdefcfaregister}{DW\-\_CFA\-\_def\-\_cfa\-\_register}&0&0x0d&ULEB128 register & \\
2249 \livelink{chap:DWCFAdefcfaoffset}{DW\-\_CFA\-\_def\-\_cfa\-\_offset}&0&0x0e &ULEB128 offset & \\
2250 \livelink{chap:DWCFAdefcfaexpression}{DW\-\_CFA\-\_def\-\_cfa\-\_expression}&0&0x0f &BLOCK \\
2251 \livelink{chap:DWCFAexpression}{DW\-\_CFA\-\_expression}&0&0x10&ULEB128 register & BLOCK \\
2253 \livelink{chap:DWCFAoffsetextendedsf}{DW\-\_CFA\-\_offset\-\_extended\-\_sf}&0&0x11&ULEB128 register&SLEB128 offset \\
2254 \livelink{chap:DWCFAdefcfasf}{DW\-\_CFA\-\_def\-\_cfa\-\_sf}&0&0x12&ULEB128 register&SLEB128 offset \\
2255 \livelink{chap:DWCFAdefcfaoffsetsf}{DW\-\_CFA\-\_def\-\_cfa\-\_offset\-\_sf}&0&0x13&SLEB128 offset & \\
2256 \livelink{chap:DWCFAvaloffset}{DW\-\_CFA\-\_val\-\_offset}&0&0x14&ULEB128&ULEB128 \\
2257 \livelink{chap:DWCFAvaloffsetsf}{DW\-\_CFA\-\_val\-\_offset\-\_sf}&0&0x15&ULEB128&SLEB128 \\
2258 \livelink{chap:DWCFAvalexpression}{DW\-\_CFA\-\_val\-\_expression}&0&0x16&ULEB128&BLOCK \\
2259 \livetarg{chap:DWCFAlouser}{DW\-\_CFA\-\_lo\-\_user}&0&0x1c & & \\
2260 \livetarg{chap:DWCFAhiuser}{DW\-\_CFA\-\_hi\-\_user}&0&0x3f & & \\
2264 \section{Non-contiguous Address Ranges}
2265 \label{datarep:noncontiguousaddressranges}
2267 Each entry in a \addtoindex{range list}
2268 (see Section \refersec{chap:noncontiguousaddressranges})
2270 \addtoindexx{base address selection entry!in range list}
2272 \addtoindexx{range list}
2273 a base address selection entry, or an end
2276 A \addtoindex{range list} entry consists of two relative addresses. The
2277 addresses are the same size as addresses on the target machine.
2279 A base address selection entry and an
2280 \addtoindex{end of list entry!in range list}
2281 end of list entry each
2282 \addtoindexx{base address selection entry!in range list}
2283 consist of two (constant or relocated) addresses. The two
2284 addresses are the same size as addresses on the target machine.
2286 For a \addtoindex{range list} to be specified, the base address of the
2287 \addtoindexx{base address selection entry!in range list}
2288 corresponding compilation unit must be defined
2289 (see Section \refersec{chap:normalandpartialcompilationunitentries}).
2292 \section{Dependencies and Constraints}
2293 \label{datarep:dependenciesandconstraints}
2295 The debugging information in this format is intended to
2297 \addtoindexx{DWARF section names!list of}
2299 the \addtoindex{.debug\_abbrev},
2300 \addtoindex{.debug\_aranges},
2301 \addtoindex{.debug\_frame},
2302 \addtoindex{.debug\_info},
2303 \addtoindex{.debug\_line},
2304 \addtoindex{.debug\_loc},
2305 \addtoindex{.debug\_macinfo},
2306 \addtoindex{.debug\_pubnames},
2307 \addtoindex{.debug\_pubtypes},
2308 \addtoindex{.debug\_ranges},
2309 \addtoindex{.debug\_str}
2311 \addtoindex{.debug\_types}
2312 sections of an object file, or equivalent
2313 separate file or database. The information is not
2314 word\dash aligned. Consequently:
2317 \item For the 32\dash bit DWARF format and a target architecture with
2318 32\dash bit addresses, an assembler or compiler must provide a way
2319 to produce 2\dash byte and 4\dash byte quantities without alignment
2320 restrictions, and the linker must be able to relocate a
2321 4\dash byte address or
2322 \addtoindexx{section offset!alignment of}
2323 section offset that occurs at an arbitrary
2326 \item For the 32\dash bit DWARF format and a target architecture with
2327 64\dash bit addresses, an assembler or compiler must provide a
2328 way to produce 2\dash byte, 4\dash byte and 8\dash byte quantities without
2329 alignment restrictions, and the linker must be able to relocate
2330 an 8\dash byte address or 4\dash byte
2331 \addtoindexx{section offset!alignment of}
2332 section offset that occurs at an
2333 arbitrary alignment.
2335 \item For the 64\dash bit DWARF format and a target architecture with
2336 32\dash bit addresses, an assembler or compiler must provide a
2337 way to produce 2\dash byte, 4\dash byte and 8\dash byte quantities without
2338 alignment restrictions, and the linker must be able to relocate
2339 a 4\dash byte address or 8\dash byte
2340 \addtoindexx{section offset!alignment of}
2341 section offset that occurs at an
2342 arbitrary alignment.
2344 \textit{It is expected that this will be required only for very large
2345 32\dash bit programs or by those architectures which support
2346 a mix of 32\dash bit and 64\dash bit code and data within the same
2349 \item For the 64\dash bit DWARF format and a target architecture with
2350 64\dash bit addresses, an assembler or compiler must provide a
2351 way to produce 2\dash byte, 4\dash byte and 8\dash byte quantities without
2352 alignment restrictions, and the linker must be able to
2353 relocate an 8\dash byte address or
2354 \addtoindexx{section offset!alignment of}
2355 section offset that occurs at
2356 an arbitrary alignment.
2359 \section{Integer Representation Names}
2360 \label{datarep:integerrepresentationnames}
2362 The sizes of the integers used in the lookup by name, lookup
2363 by address, line number and call frame information sections
2365 Table 41 \refersec{tab:integerrepresentationnames}.
2368 \setlength{\extrarowheight}{0.1cm}
2369 \begin{longtable}{c|l}
2370 \caption{Integer Representation Names} \label{tab:integerrepresentationnames}\\
2371 \hline \bfseries Representation Name&\bfseries Representation \\ \hline
2373 \bfseries Representation Name&\bfseries Representation\\ \hline
2375 \hline \emph{Continued on next page}
2380 \addtoindex{sbyte}& signed, 1\dash byte integer \\
2381 \addtoindex{ubyte}&unsigned, 1\dash byte integer \\
2382 \addtoindex{uhalf}&unsigned, 2\dash byte integer \\
2383 \addtoindex{uword}&unsigned, 4\dash byte integer \\
2389 \section{Type Signature Computation}
2390 \label{datarep:typesignaturecomputation}
2392 A type signature is computed only by the DWARF producer;
2393 \addtoindexx{type signature computation}
2394 it is used by a DWARF consumer to resolve type references to
2395 the type definitions that are contained in
2396 \addtoindexx{type unit}
2399 The type signature for a type T0 is formed from the
2400 \addtoindex{MD5 hash}
2401 of a flattened description of the type. The flattened
2402 description of the type is a byte sequence derived from the
2403 DWARF encoding of the type as follows:
2405 \begin{enumerate}[1.]
2407 \item Start with an empty sequence S and a list V of visited
2408 types, where V is initialized to a list containing the type
2409 T0 as its single element. Elements in V are indexed from 1,
2412 \item If the debugging information entry represents a type that
2413 is nested inside another type or a namespace, append to S
2414 the type\textquoteright s context as follows: For each surrounding type
2415 or namespace, beginning with the outermost such construct,
2416 append the letter 'C', the DWARF tag of the construct, and
2417 the name (taken from
2418 \addtoindexx{name attribute}
2419 the \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute) of the type
2420 \addtoindexx{name attribute}
2421 or namespace (including its trailing null byte).
2423 \item Append to S the letter 'D', followed by the DWARF tag of
2424 the debugging information entry.
2426 \item For each of the attributes in
2427 Table \refersec{tab:attributesusedintypesignaturecomputation}
2429 the debugging information entry, in the order listed,
2430 append to S a marker letter (see below), the DWARF attribute
2431 code, and the attribute value.
2434 \caption{Attributes used in type signature computation}
2435 \label{tab:attributesusedintypesignaturecomputation}
2436 \simplerule[\textwidth]
2438 \autocols[0pt]{c}{2}{l}{
2439 \livelink{chap:DWATname}{DW\-\_AT\-\_name},
2440 \livelink{chap:DWATaccessibility}{DW\-\_AT\-\_accessibility},
2441 \livelink{chap:DWATaddressclass}{DW\-\_AT\-\_address\-\_class},
2442 \livelink{chap:DWATallocated}{DW\-\_AT\-\_allocated},
2443 \livelink{chap:DWATartificial}{DW\-\_AT\-\_artificial},
2444 \livelink{chap:DWATassociated}{DW\-\_AT\-\_associated},
2445 \livelink{chap:DWATbinaryscale}{DW\-\_AT\-\_binary\-\_scale},
2446 \livelink{chap:DWATbitoffset}{DW\-\_AT\-\_bit\-\_offset},
2447 \livelink{chap:DWATbitsize}{DW\-\_AT\-\_bit\-\_size},
2448 \livelink{chap:DWATbitstride}{DW\-\_AT\-\_bit\-\_stride},
2449 \livelink{chap:DWATbytesize}{DW\-\_AT\-\_byte\-\_size},
2450 \livelink{chap:DWATbytestride}{DW\-\_AT\-\_byte\-\_stride},
2451 \livelink{chap:DWATconstexpr}{DW\-\_AT\-\_const\-\_expr},
2452 \livelink{chap:DWATconstvalue}{DW\-\_AT\-\_const\-\_value},
2453 \livelink{chap:DWATcontainingtype}{DW\-\_AT\-\_containing\-\_type},
2454 \livelink{chap:DWATcount}{DW\-\_AT\-\_count},
2455 \livelink{chap:DWATdatabitoffset}{DW\-\_AT\-\_data\-\_bit\-\_offset},
2456 \livelink{chap:DWATdatalocation}{DW\-\_AT\-\_data\-\_location},
2457 \livelink{chap:DWATdatamemberlocation}{DW\-\_AT\-\_data\-\_member\-\_location},
2458 \livelink{chap:DWATdecimalscale}{DW\-\_AT\-\_decimal\-\_scale},
2459 \livelink{chap:DWATdecimalsign}{DW\-\_AT\-\_decimal\-\_sign},
2460 \livelink{chap:DWATdefaultvalue}{DW\-\_AT\-\_default\-\_value},
2461 \livelink{chap:DWATdigitcount}{DW\-\_AT\-\_digit\-\_count},
2462 \livelink{chap:DWATdiscr}{DW\-\_AT\-\_discr},
2463 \livelink{chap:DWATdiscrlist}{DW\-\_AT\-\_discr\-\_list},
2464 \livelink{chap:DWATdiscrvalue}{DW\-\_AT\-\_discr\-\_value},
2465 \livelink{chap:DWATencoding}{DW\-\_AT\-\_encoding},
2466 \livelink{chap:DWATenumclass}{DW\-\_AT\-\_enum\-\_class},
2467 \livelink{chap:DWATendianity}{DW\-\_AT\-\_endianity},
2468 \livelink{chap:DWATexplicit}{DW\-\_AT\-\_explicit},
2469 \livelink{chap:DWATisoptional}{DW\-\_AT\-\_is\-\_optional},
2470 \livelink{chap:DWATlocation}{DW\-\_AT\-\_location},
2471 \livelink{chap:DWATlowerbound}{DW\-\_AT\-\_lower\-\_bound},
2472 \livelink{chap:DWATmutable}{DW\-\_AT\-\_mutable},
2473 \livelink{chap:DWATordering}{DW\-\_AT\-\_ordering},
2474 \livelink{chap:DWATpicturestring}{DW\-\_AT\-\_picture\-\_string},
2475 \livelink{chap:DWATprototyped}{DW\-\_AT\-\_prototyped},
2476 \livelink{chap:DWATsmall}{DW\-\_AT\-\_small},
2477 \livelink{chap:DWATsegment}{DW\-\_AT\-\_segment},
2478 \livelink{chap:DWATstringlength}{DW\-\_AT\-\_string\-\_length},
2479 \livelink{chap:DWATthreadsscaled}{DW\-\_AT\-\_threads\-\_scaled},
2480 \livelink{chap:DWATupperbound}{DW\-\_AT\-\_upper\-\_bound},
2481 \livelink{chap:DWATuselocation}{DW\-\_AT\-\_use\-\_location},
2482 \livelink{chap:DWATuseUTF8}{DW\-\_AT\-\_use\-\_UTF8},
2483 \livelink{chap:DWATvariableparameter}{DW\-\_AT\-\_variable\-\_parameter},
2484 \livelink{chap:DWATvirtuality}{DW\-\_AT\-\_virtuality},
2485 \livelink{chap:DWATvisibility}{DW\-\_AT\-\_visibility},
2486 \livelink{chap:DWATvtableelemlocation}{DW\-\_AT\-\_vtable\-\_elem\-\_location}
2489 \simplerule[\textwidth]
2492 Note that except for the initial
2493 \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute,
2494 \addtoindexx{name attribute}
2495 attributes are appended in order according to the alphabetical
2496 spelling of their identifier.
2498 If an implementation defines any vendor-specific attributes,
2499 any such attributes that are essential to the definition of
2500 the type should also be included at the end of the above list,
2501 in their own alphabetical suborder.
2503 An attribute that refers to another type entry T is processed
2504 as follows: (a) If T is in the list V at some V[x], use the
2505 letter 'R' as the marker and use the unsigned LEB128 encoding
2506 of x as the attribute value; otherwise, (b) use the letter 'T'
2507 as the marker, process the type T recursively by performing
2508 Steps 2 through 7, and use the result as the attribute value.
2510 Other attribute values use the letter 'A' as the marker, and
2511 the value consists of the form code (encoded as an unsigned
2512 LEB128 value) followed by the encoding of the value according
2513 to the form code. To ensure reproducibility of the signature,
2514 the set of forms used in the signature computation is limited
2515 to the following: \livelink{chap:DWFORMsdata}{DW\-\_FORM\-\_sdata},
2516 \livelink{chap:DWFORMflag}{DW\-\_FORM\-\_flag},
2517 \livelink{chap:DWFORMstring}{DW\-\_FORM\-\_string},
2518 and \livelink{chap:DWFORMblock}{DW\-\_FORM\-\_block}.
2520 \item If the tag in Step 3 is one of \livelink{chap:DWTAGpointertype}{DW\-\_TAG\-\_pointer\-\_type},
2521 \livelink{chap:DWTAGreferencetype}{DW\-\_TAG\-\_reference\-\_type},
2522 \livelink{chap:DWTAGrvaluereferencetype}{DW\-\_TAG\-\_rvalue\-\_reference\-\_type},
2523 \livelink{chap:DWTAGptrtomembertype}{DW\-\_TAG\-\_ptr\-\_to\-\_member\-\_type},
2524 or \livelink{chap:DWTAGfriend}{DW\-\_TAG\-\_friend}, and the referenced
2525 type (via the \livelink{chap:DWATtype}{DW\-\_AT\-\_type} or
2526 \livelink{chap:DWATfriend}{DW\-\_AT\-\_friend} attribute) has a
2527 \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute, append to S the letter 'N', the DWARF
2528 attribute code (\livelink{chap:DWATtype}{DW\-\_AT\-\_type} or
2529 \livelink{chap:DWATfriend}{DW\-\_AT\-\_friend}), the context of
2530 the type (according to the method in Step 2), the letter 'E',
2531 and the name of the type. For \livelink{chap:DWTAGfriend}{DW\-\_TAG\-\_friend}, if the referenced
2532 entry is a \livelink{chap:DWTAGsubprogram}{DW\-\_TAG\-\_subprogram}, the context is omitted and the
2533 name to be used is the ABI-specific name of the subprogram
2534 (e.g., the mangled linker name).
2537 \item 6.If the tag in Step 3 is not one of \livelink{chap:DWTAGpointertype}{DW\-\_TAG\-\_pointer\-\_type},
2538 \livelink{chap:DWTAGreferencetype}{DW\-\_TAG\-\_reference\-\_type},
2539 \livelink{chap:DWTAGrvaluereferencetype}{DW\-\_TAG\-\_rvalue\-\_reference\-\_type},
2540 \livelink{chap:DWTAGptrtomembertype}{DW\-\_TAG\-\_ptr\-\_to\-\_member\-\_type}, or
2541 \livelink{chap:DWTAGfriend}{DW\-\_TAG\-\_friend}, but has
2542 a \livelink{chap:DWATtype}{DW\-\_AT\-\_type} attribute, or if the referenced type (via
2543 the \livelink{chap:DWATtype}{DW\-\_AT\-\_type} or
2544 \livelink{chap:DWATfriend}{DW\-\_AT\-\_friend} attribute) does not have a
2545 \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute, the attribute is processed according to
2546 the method in Step 4 for an attribute that refers to another
2550 \item Visit each child C of the debugging information
2551 entry as follows: If C is a nested type entry or a member
2552 function entry, and has
2553 a \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute, append to
2554 \addtoindexx{name attribute}
2555 S the letter 'S', the tag of C, and its name; otherwise,
2556 process C recursively by performing Steps 3 through 7,
2557 appending the result to S. Following the last child (or if
2558 there are no children), append a zero byte.
2563 For the purposes of this algorithm, if a debugging information
2565 \livelink{chap:DWATspecification}{DW\-\_AT\-\_specification}
2566 attribute that refers to
2567 another entry D (which has a
2568 \livelink{chap:DWATdeclaration}{DW\-\_AT\-\_declaration}
2570 then S inherits the attributes and children of D, and S is
2571 processed as if those attributes and children were present in
2572 the entry S. Exception: if a particular attribute is found in
2573 both S and D, the attribute in S is used and the corresponding
2574 one in D is ignored.
2576 DWARF tag and attribute codes are appended to the sequence
2577 as unsigned LEB128 values, using the values defined earlier
2580 \textit{A grammar describing this computation may be found in
2581 Appendix \refersec{app:typesignaturecomputationgrammar}.
2584 \textit{An attribute that refers to another type entry should
2585 be recursively processed or replaced with the name of the
2586 referent (in Step 4, 5 or 6). If neither treatment applies to
2587 an attribute that references another type entry, the entry
2588 that contains that attribute should not be considered for a
2589 separate \addtoindex{type unit}.}
2591 \textit{If a debugging information entry contains an attribute from
2592 the list above that would require an unsupported form, that
2593 entry should not be considered for a separate
2594 \addtoindex{type unit}.}
2596 \textit{A type should be considered for a separate
2597 \addtoindex{type unit} only
2598 if all of the type entries that it contains or refers to in
2599 Steps 6 and 7 can themselves each be considered for a separate
2600 \addtoindex{type unit}.}
2602 Where the DWARF producer may reasonably choose two or more
2603 different forms for a given attribute, it should choose
2604 the simplest possible form in computing the signature. (For
2605 example, a constant value should be preferred to a location
2606 expression when possible.)
2608 Once the string S has been formed from the DWARF encoding,
2609 an \addtoindex{MD5 hash} is computed for the string and the lower 64 bits
2610 are taken as the type signature.
2612 \textit{The string S is intended to be a flattened representation of
2613 the type that uniquely identifies that type (i.e., a different
2614 type is highly unlikely to produce the same string).}
2616 \textit{A debugging information entry should not be placed in a
2617 separate \addtoindex{type unit}
2618 if any of the following apply:}
2622 \item \textit{The entry has an attribute whose value is a location
2623 expression, and the location expression contains a reference to
2624 another debugging information entry (e.g., a \livelink{chap:DWOPcallref}{DW\-\_OP\-\_call\-\_ref}
2625 operator), as it is unlikely that the entry will remain
2626 identical across compilation units.}
2628 \item \textit{The entry has an attribute whose value refers
2629 to a code location or a \addtoindex{location list}.}
2631 \item \textit{The entry has an attribute whose value refers
2632 to another debugging information entry that does not represent
2638 \textit{Certain attributes are not included in the type signature:}
2641 \item \textit{The \livelink{chap:DWATdeclaration}{DW\-\_AT\-\_declaration} attribute is not included because it
2642 indicates that the debugging information entry represents an
2643 incomplete declaration, and incomplete declarations should
2645 \addtoindexx{type unit}
2646 separate type units.}
2648 \item \textit{The \livelink{chap:DWATdescription}{DW\-\_AT\-\_description} attribute is not included because
2649 it does not provide any information unique to the defining
2650 declaration of the type.}
2652 \item \textit{The \livelink{chap:DWATdeclfile}{DW\-\_AT\-\_decl\-\_file},
2653 \livelink{chap:DWATdeclline}{DW\-\_AT\-\_decl\-\_line}, and
2654 \livelink{chap:DWATdeclcolumn}{DW\-\_AT\-\_decl\-\_column} attributes are not included because they
2655 may vary from one source file to the next, and would prevent
2656 two otherwise identical type declarations from producing the
2657 \addtoindexx{MD5 hash}
2660 \item \textit{The \livelink{chap:DWATobjectpointer}{DW\-\_AT\-\_object\-\_pointer} attribute is not included
2661 because the information it provides is not necessary for the
2662 computation of a unique type signature.}
2666 \textit{Nested types and some types referred to by a debugging
2667 information entry are encoded by name rather than by recursively
2668 encoding the type to allow for cases where a complete definition
2669 of the type might not be available in all compilation units.}
2671 \textit{If a type definition contains the definition of a member function,
2672 it cannot be moved as is into a type unit, because the member function
2673 contains attributes that are unique to that compilation unit.
2674 Such a type definition can be moved to a type unit by rewriting the DIE tree,
2675 moving the member function declaration into a separate declaration tree,
2676 and replacing the function definition in the type with a non-defining
2677 declaration of the function (as if the function had been defined out of
2680 An example that illustrates the computation of an MD5 hash may be found in
2681 Appendix \refersec{app:usingtypeunits}.