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’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:
158 \begin{enumerate}[1.]
160 \item In the 32\dash bit DWARF format, an
161 \addtoindex{initial length field}
163 \addtoindex{initial length field!encoding}
164 Section \refersec{datarep:initiallengthvalues})
165 is an unsigned 32\dash bit integer (which
166 must be less than 0xfffffff0); in the 64\dash bit DWARF format,
167 an \addtoindex{initial length field} is 96 bits in size,
170 \item The first 32\dash bits have the value 0xffffffff.
172 \item The following 64\dash bits contain the actual length
173 represented as an unsigned 64\dash bit integer.
176 \textit{This representation allows a DWARF consumer to dynamically
177 detect that a DWARF section contribution is using the 64\dash bit
178 format and to adapt its processing accordingly.}
180 \item Section offset and section length
181 \addtoindexx{section length!use in headers}
183 \addtoindexx{section offset!use in headers}
184 in the headers of DWARF sections (other
185 \addtoindex{initial length field}
187 \addtoindex{initial length}
188 fields) are listed following. In the 32\dash bit DWARF format these
189 are 32\dash bit unsigned integer values; in the 64\dash bit DWARF format,
191 \addtoindexx{section length!in .debug\_aranges header}
193 \addtoindexx{section length!in .debug\_pubnames header}
195 \addtoindexx{section length!in .debug\_pubtypes header}
196 unsigned integer values.
200 Section &Name & Role \\ \hline
201 \addtoindex{.debug\_ranges} & \addtoindex{debug\_info\_offset} & offset in \addtoindex{.debug\_info} \\
202 \addtoindex{.debug\_frame}/CIE & \addtoindex{CIE\_id} & CIE distinguished value \\
203 \addtoindex{.debug\_frame}/FDE & \addtoindex{CIE\_pointer} & offset in \addtoindex{.debug\_frame} \\
204 \addtoindex{.debug\_info} & \addtoindex{debug\_abbrev\_offset} & offset in \addtoindex{.debug\_abbrev} \\
205 \addtoindex{.debug\_line} & \addtoindex{header\_length} & length of header itself \\
206 \addtoindex{.debug\_pubnames} & \addtoindex{debug\_info\_offset} & offset in \addtoindex{.debug\_info} \\
207 & \addtoindex{debug\_info\_length} & length of \addtoindex{.debug\_info} \\
209 \addtoindex{.debug\_pubtypes} & \addtoindex{debug\_info\_offset} & offset in \addtoindex{.debug\_info} \\
210 & \addtoindex{debug\_info\_length} & length of \addtoindex{.debug\_info} \\
212 \addtoindex{.debug\_types} & \addtoindex{debug\_abbrev\_offset} & offset in \addtoindex{.debug\_info} \\
213 & \addtoindex{type\_offset} & offset in of \addtoindex{.debug\_types} \\
218 \textit{The CIE\_id field in a CIE structure must be 64 bits because
219 it overlays the CIE\_pointer in a FDE structure; this implicit
220 union must be accessed to distinguish whether a CIE or FDE is
221 present, consequently, these two fields must exactly overlay
222 each other (both offset and size).}
224 \item Within the body of the \addtoindex{.debug\_info} or \addtoindex{.debug\_types}
225 section, certain forms of attribute value depend on the choice
226 of DWARF format as follows. For the 32\dash bit DWARF format,
227 the value is a 32\dash bit unsigned integer; for the 64\dash bit DWARF
228 format, the value is a 64\dash bit unsigned integer.
231 Form & Role \\ \hline
232 \livelink{chap:DWFORMrefaddr}{DW\-\_FORM\-\_ref\-\_addr}& offset in \addtoindex{.debug\_info} \\
233 \livetarg{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}& offset in a section other than \addtoindex{.debug\_info} or \addtoindex{.debug\_str} \\
234 \livelink{chap:DWFORMstrp}{DW\-\_FORM\-\_strp}&offset in \addtoindex{.debug\_str} \\
235 \livelink{chap:DWOPcallref}{DW\-\_OP\-\_call\-\_ref}&offset in \addtoindex{.debug\_info} \\
239 \item Within the body of the \addtoindex{.debug\_pubnames} and
240 \addtoindex{.debug\_pubtypes}
241 sections, the representation of the first field
242 of each tuple (which represents an offset in the
243 \addtoindex{.debug\_info}
244 section) depends on the DWARF format as follows: in the
245 32\dash bit DWARF format, this field is a 32\dash bit unsigned integer;
246 in the 64\dash bit DWARF format, it is a 64\dash bit unsigned integer.
251 The 32\dash bit and 64\dash bit DWARF format conventions must not be
252 intermixed within a single compilation unit.
254 \textit{Attribute values and section header fields that represent
255 addresses in the target program are not affected by these
258 A DWARF consumer that supports the 64\dash bit DWARF format must
259 support executables in which some compilation units use the
260 32\dash bit format and others use the 64\dash bit format provided that
261 the combination links correctly (that is, provided that there
262 are no link\dash time errors due to truncation or overflow). (An
263 implementation is not required to guarantee detection and
264 reporting of all such errors.)
266 \textit{It is expected that DWARF producing compilers will not use
267 the 64\dash bit format by default. In most cases, the division of
268 even very large applications into a number of executable and
269 shared objects will suffice to assure that the DWARF sections
270 within each individual linked object are less than 4 GBytes
271 in size. However, for those cases where needed, the 64\dash bit
272 format allows the unusual case to be handled as well. Even
273 in this case, it is expected that only application supplied
274 objects will need to be compiled using the 64\dash bit format;
275 separate 32\dash bit format versions of system supplied shared
276 executable libraries can still be used.}
280 \section{Format of Debugging Information}
281 \label{datarep:formatofdebugginginformation}
283 For each compilation unit compiled with a DWARF producer,
284 a contribution is made to the \addtoindex{.debug\_info} section of
285 the object file. Each such contribution consists of a
286 compilation unit header
287 (see Section \refersec{datarep:compilationunitheader})
289 single \livelink{chap:DWTAGcompileunit}{DW\-\_TAG\-\_compile\-\_unit} or \livelink{chap:DWTAGpartialunit}{DW\-\_TAG\-\_partial\-\_unit} debugging
290 information entry, together with its children.
292 For each type defined in a compilation unit, a contribution may
293 be made to the \addtoindex{.debug\_types}
294 section of the object file. Each
295 such contribution consists of a
296 \addtoindex{type unit} header
297 (see Section \refersec{datarep:typeunitheader})
298 followed by a \livelink{chap:DWTAGtypeunit}{DW\-\_TAG\-\_type\-\_unit} entry, together with
301 Each debugging information entry begins with a code that
302 represents an entry in a separate
303 \addtoindex{abbreviations table}. This
304 code is followed directly by a series of attribute values.
306 The appropriate entry in the
307 \addtoindex{abbreviations table} guides the
308 interpretation of the information contained directly in the
309 \addtoindex{.debug\_info} or
310 \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 A 4\dash byte or 12\dash byte
326 \addtoindexx{initial length}
327 unsigned integer representing the length
328 of the \addtoindex{.debug\_info}
329 contribution for that compilation unit,
330 not including the length field itself. In the 32\dash bit DWARF
331 format, this is a 4\dash byte unsigned integer (which must be less
332 than 0xfffffff0); in the 64\dash bit DWARF format, this consists
333 of the 4\dash byte value 0xffffffff followed by an 8\dash byte unsigned
334 integer that gives the actual length
335 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
337 \item version (uhalf)
338 A 2\dash byte unsigned integer representing the version of the
339 DWARF information for the compilation unit\addtoindexx{version number!compilation unit}
340 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
341 The value in this field is 4.
343 \item \addtoindex{debug\_abbrev\_offset} (section offset) \\
345 \addtoindexx{section offset!in .debug\_info header}
346 4\dash byte or 8\dash byte unsigned offset into the
347 \addtoindex{.debug\_abbrev}
348 section. This offset associates the compilation unit with a
349 particular set of debugging information entry abbreviations. In
350 the 32\dash bit DWARF format, this is a 4\dash byte unsigned length;
351 in the 64\dash bit DWARF format, this is an 8\dash byte unsigned length
352 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
354 \item address\_size (ubyte) \\
355 A 1\dash byte unsigned integer representing the size in bytes of
356 \addtoindexx{address\_size}
357 an address on the target architecture. If the system uses
358 \addtoindexx{address space!segmented}
359 segmented addressing, this value represents the size of the
360 offset portion of an address.
367 \subsubsection{Type Unit Header}
368 \label{datarep:typeunitheader}
370 The header for the series of debugging information entries
371 contributing to the description of a type that has been
372 placed in its own \addtoindex{type unit}, within the
373 \addtoindex{.debug\_types} section,
374 consists of the following information:
376 \begin{enumerate}[1.]
378 \item unit\_length (initial length) \\
379 A 4\dash byte or 12\dash byte unsigned integer
380 \addtoindexx{initial length}
381 representing the length
382 of the \addtoindex{.debug\_types} contribution for that compilation unit,
383 not including the length field itself. In the 32\dash bit DWARF
384 format, this is a 4\dash byte unsigned integer (which must be
385 less than 0xfffffff0); in the 64\dash bit DWARF format, this
386 consists of the 4\dash byte value 0xffffffff followed by an
387 8\dash byte unsigned integer that gives the actual length
388 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
390 \item version (uhalf)
391 A 2\dash byte unsigned integer representing the version of the
392 DWARF information for the
393 compilation unit\addtoindexx{version number!type unit}
394 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
395 The value in this field is 4.
397 \item \addtoindex{debug\_abbrev\_offset} (section offset) \\
399 \addtoindexx{section offset!in .debug\_types header}
400 4\dash byte or 8\dash byte unsigned offset into the
401 \addtoindex{.debug\_abbrev}
402 section. This offset associates the compilation unit with a
403 particular set of debugging information entry abbreviations. In
404 the 32\dash bit DWARF format, this is a 4\dash byte unsigned length;
405 in the 64\dash bit DWARF format, this is an 8\dash byte unsigned length
406 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
408 \item address\_size (ubyte) \\
409 A 1\dash byte unsigned integer representing the size
410 \addtoindexx{size of an address}
412 \addtoindexx{address\_size}
413 an address on the target architecture. If the system uses
414 \addtoindexx{address space!segmented}
415 segmented addressing, this value represents the size of the
416 offset portion of an address.
419 \item type\_signature (8\dash byte unsigned integer) \\
420 \addtoindexx{type signature}
422 \addtoindexx{type\_signature}
423 64\dash bit unique signature of the type described in this type
426 \textit{An attribute that refers(using \livelink{chap:DWFORMrefsig8}{DW\-\_FORM\-\_ref\-\_sig8}) to
427 the primary type contained in
428 this \addtoindex{type unit} uses this value.}
431 \item type\_offset (section offset) \\
432 \addtoindexx{type\_offset}
433 A 4\dash byte or 8\dash byte unsigned offset
434 \addtoindexx{section offset!in .debug\_types header}
435 relative to the beginning
436 of the \addtoindex{type unit} header.
437 This offset refers to the debugging
438 information entry that describes the type. Because the type
439 may be nested inside a namespace or other structures, and may
440 contain references to other types that have not been placed in
441 separate type units, it is not necessarily either the first or
442 the only entry in the type unit. In the 32\dash bit DWARF format,
443 this is a 4\dash byte unsigned length; in the 64\dash bit DWARF format,
444 this is an 8\dash byte unsigned length
445 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
449 \subsection{Debugging Information Entry}
450 \label{datarep:debugginginformationentry}
452 Each debugging information entry begins with an unsigned LEB128
453 number containing the abbreviation code for the entry. This
454 code represents an entry within the abbreviations table
455 associated with the compilation unit containing this entry. The
456 abbreviation code is followed by a series of attribute values.
458 On some architectures, there are alignment constraints on
459 section boundaries. To make it easier to pad debugging
460 information sections to satisfy such constraints, the
461 abbreviation code 0 is reserved. Debugging information entries
462 consisting of only the abbreviation code 0 are considered
465 \subsection{Abbreviations Tables}
466 \label{datarep:abbreviationstables}
468 The abbreviations tables for all compilation units
469 are contained in a separate object file section called
470 \addtoindex{.debug\_abbrev}.
471 As mentioned before, multiple compilation
472 units may share the same abbreviations table.
474 The abbreviations table for a single compilation unit consists
475 of a series of abbreviation declarations. Each declaration
476 specifies the tag and attributes for a particular form of
477 debugging information entry. Each declaration begins with
478 an unsigned LEB128 number representing the abbreviation
479 code itself. It is this code that appears at the beginning
480 of a debugging information entry in the
481 \addtoindex{.debug\_info} or
482 \addtoindex{.debug\_types}
483 section. As described above, the abbreviation
484 code 0 is reserved for null debugging information entries. The
485 abbreviation code is followed by another unsigned LEB128
486 number that encodes the entry’s tag. The encodings for the
487 tag names are given in
488 Table \refersec{tab:tagencodings}.
490 Following the tag encoding is a 1\dash byte value that determines
491 whether a debugging information entry using this abbreviation
492 has child entries or not. If the value is
493 \livetarg{chap:DWCHILDRENyes}{DW\-\_CHILDREN\-\_yes},
494 the next physically succeeding entry of any debugging
495 information entry using this abbreviation is the first
496 child of that entry. If the 1\dash byte value following the
497 abbreviation’s tag encoding is
498 \livetarg{chap:DWCHILDRENno}{DW\-\_CHILDREN\-\_no}, the next
499 physically succeeding entry of any debugging information entry
500 using this abbreviation is a sibling of that entry. (Either
501 the first child or sibling entries may be null entries). The
502 encodings for the child determination byte are given in
503 Table \refersec{tab:childdeterminationencodings}
505 Section \refersec{chap:relationshipofdebugginginformationentries},
507 sibling entries is terminated by a null entry.)
509 Finally, the child encoding is followed by a series of
510 attribute specifications. Each attribute specification
511 consists of two parts. The first part is an unsigned LEB128
512 number representing the attribute’s name. The second part
513 is an unsigned LEB128 number representing the attribute’s
514 form. The series of attribute specifications ends with an
515 entry containing 0 for the name and 0 for the form.
518 \livetarg{chap:DWFORMindirect}{DW\-\_FORM\-\_indirect} is a special case. For
519 attributes with this form, the attribute value itself in the
520 \addtoindex{.debug\_info} or
521 \addtoindex{.debug\_types}
522 section begins with an unsigned
523 LEB128 number that represents its form. This allows producers
524 to choose forms for particular attributes
525 \addtoindexx{abbreviations table!dynamic forms in}
527 without having to add a new entry to the abbreviations table.
529 The abbreviations for a given compilation unit end with an
530 entry consisting of a 0 byte for the abbreviation code.
533 Appendix \refersec{app:compilationunitsandabbreviationstableexample}
534 for a depiction of the organization of the
535 debugging information.
537 \subsection{Attribute Encodings}
538 \label{datarep:attributeencodings}
540 The encodings for the attribute names are given in
541 Table \refersec{tab:attributeencodings}.
543 The attribute form governs how the value of the attribute is
544 encoded. There are nine classes of form, listed below. Each
545 class is a set of forms which have related representations
546 and which are given a common interpretation according to the
547 attribute in which the form is used.
549 Form \livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}
551 \addtoindexx{rangelistptr class}
553 \addtoindexx{macptr class}
555 \addtoindexx{loclistptr class}
557 \addtoindexx{lineptr class}
558 namely \livelink{chap:lineptr}{lineptr},
559 \livelink{chap:loclistptr}{loclistptr},
560 \livelink{chap:macptr}{macptr} or
561 \livelink{chap:rangelistptr}{rangelistptr}; the list
562 of classes allowed by the applicable attribute in
563 Table \refersec{tab:attributeencodings}
564 determines the class of the form.
566 \textit{In DWARF V3 the forms \livelink{chap:DWFORMdata4}{DW\-\_FORM\-\_data4} and \livelink{chap:DWFORMdata8}{DW\-\_FORM\-\_data8} were
567 \addtoindexx{lineptr class}
569 \addtoindexx{rangelistptr class}
571 \addtoindexx{macptr class}
573 \addtoindexx{loclistptr class}
574 class constant \addtoindexx{constant class}
575 or one of the classes
576 \livelink{chap:lineptr}{lineptr},
577 \livelink{chap:loclistptr}{loclistptr},
578 \livelink{chap:macptr}{macptr} or
579 \livelink{chap:rangelistptr}{rangelistptr}, depending on context. In
581 \livelink{chap:DWFORMdata4}{DW\-\_FORM\-\_data4} and
582 \livelink{chap:DWFORMdata8}{DW\-\_FORM\-\_data8} are members of class
583 constant in all cases.
585 \livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset} replaces
586 their usage for the other classes.}
588 Each possible form belongs to one or more of the following classes:
591 \item \livelinki{chap:DWATaddressclass}{address}{address class} \\
592 Represented as an object of appropriate size to hold an
593 address on the target machine
594 (\livetarg{chap:DWFORMaddr}{DW\-\_FORM\-\_addr}).
596 encoded in the compilation unit header
597 (see Section \refersec{datarep:compilationunitheader}).
598 This address is relocatable in a relocatable object file and
599 is relocated in an executable file or shared object.
601 \item \livelink{chap:block}{block} \\
602 Blocks come in four forms:
604 \begin{myindentpara}{1cm}
605 A 1\dash byte length followed by 0 to 255 contiguous information
606 bytes (\livetarg{chap:DWFORMblock1}{DW\-\_FORM\-\_block1}).
609 \begin{myindentpara}{1cm}
610 A 2\dash byte length followed by 0 to 65,535 contiguous information
611 bytes (\livetarg{chap:DWFORMblock2}{DW\-\_FORM\-\_block2}).
615 \begin{myindentpara}{1cm}
616 A 4\dash byte length followed by 0 to 4,294,967,295 contiguous
617 information bytes (\livetarg{chap:DWFORMblock4}{DW\-\_FORM\-\_block4}).
621 \begin{myindentpara}{1cm}
622 An unsigned LEB128 length followed by the number of bytes
623 specified by the length (\livetarg{chap:DWFORMblock}{DW\-\_FORM\-\_block}).
626 In all forms, the length is the number of information bytes
627 that follow. The information bytes may contain any mixture
628 of relocated (or relocatable) addresses, references to other
629 debugging information entries or data bytes.
632 There are six forms of constants. There are fixed length
633 constant data forms for one, two, four and eight byte values
635 \livetarg{chap:DWFORMdata1}{DW\-\_FORM\-\_data1},
636 \livetarg{chap:DWFORMdata2}{DW\-\_FORM\-\_data2},
637 \livetarg{chap:DWFORMdata4}{DW\-\_FORM\-\_data4},
638 and \livetarg{chap:DWFORMdata8}{DW\-\_FORM\-\_data8}).
639 There are also variable length constant
640 data forms encoded using LEB128 numbers (see below). Both
641 signed (\livetarg{chap:DWFORMsdata}{DW\-\_FORM\-\_sdata}) and unsigned
642 (\livetarg{chap:DWFORMudata}{DW\-\_FORM\-\_udata}) variable
643 length constants are available
645 The data in \livelink{chap:DWFORMdata1}{DW\-\_FORM\-\_data1},
646 \livelink{chap:DWFORMdata2}{DW\-\_FORM\-\_data2},
647 \livelink{chap:DWFORMdata4}{DW\-\_FORM\-\_data4} and
648 \livelink{chap:DWFORMdata8}{DW\-\_FORM\-\_data8}
649 can be anything. Depending on context, it may
650 be a signed integer, an unsigned integer, a floating\dash point
651 constant, or anything else. A consumer must use context to
652 know how to interpret the bits, which if they are target
653 machine data (such as an integer or floating point constant)
654 will be in target machine byte\dash order.
656 \textit{If one of the \livetarg{chap:DWFORMdata}{DW\-\_FORM\-\_data}<n> forms is used to represent a
657 signed or unsigned integer, it can be hard for a consumer
658 to discover the context necessary to determine which
659 interpretation is intended. Producers are therefore strongly
660 encouraged to use \livelink{chap:DWFORMsdata}{DW\-\_FORM\-\_sdata} or
661 \livelink{chap:DWFORMudata}{DW\-\_FORM\-\_udata} for signed and
662 unsigned integers respectively, rather than
663 \livelink{chap:DWFORMdata}{DW\-\_FORM\-\_data} \textless n \textgreater.}
666 \item \livelink{chap:exprloc}{exprloc} \\
667 This is an unsigned LEB128 length followed by the
668 number of information bytes specified by the length
669 (\livetarg{chap:DWFORMexprloc}{DW\-\_FORM\-\_exprloc}).
670 The information bytes contain a DWARF
672 (see Section \refersec{chap:dwarfexpressions})
673 or location description
674 (see Section \refersec{chap:locationdescriptions}).
676 \item \livelink{chap:flag}{flag} \\
677 A flag \addtoindexx{flag class}
678 is represented explicitly as a single byte of data
679 (\livetarg{chap:DWFORMflag}{DW\-\_FORM\-\_flag}) or
680 implicitly (\livetarg{chap:DWFORMflagpresent}{DW\-\_FORM\-\_flag\-\_present}).
682 first case, if the \nolink{flag} has value zero, it indicates the
683 absence of the attribute; if the \nolink{flag} has a non\dash zero value,
684 it indicates the presence of the attribute. In the second
685 case, the attribute is implicitly indicated as present, and
686 no value is encoded in the debugging information entry itself.
688 \item \livelink{chap:lineptr}{lineptr} \\
689 This is an offset into
690 \addtoindexx{section offset!in class lineptr value}
692 \addtoindex{.debug\_line} section
693 (\livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}).
694 It consists of an offset from the
696 \addtoindex{.debug\_line}
697 section to the first byte of
698 the data making up the line number list for the compilation
700 It is relocatable in a relocatable object file, and
701 relocated in an executable or shared object. In the 32\dash bit
702 DWARF format, this offset is a 4\dash byte unsigned value;
703 in the 64\dash bit DWARF format, it is an 8\dash byte unsigned value
704 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
707 \item \livelink{chap:loclistptr}{loclistptr} \\
708 This is an offset into the
709 \addtoindex{.debug\_loc}
711 (\livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}).
712 It consists of an offset from the
713 \addtoindexx{section offset!in class loclistptr value}
715 \addtoindex{.debug\_loc}
716 section to the first byte of
717 the data making up the
718 \addtoindex{location list} for the compilation
720 It is relocatable in a relocatable object file, and
721 relocated in an executable or shared object. In the 32\dash bit
722 DWARF format, this offset is a 4\dash byte unsigned value;
723 in the 64\dash bit DWARF format, it is an 8\dash byte unsigned value
724 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
727 \item \livelink{chap:macptr}{macptr} \\
729 \addtoindexx{section offset!in class macptr value}
731 \addtoindex{.debug\_macinfo} section
732 (\livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}). It consists of an offset from the
733 beginning of the \addtoindex{.debug\_macinfo}
734 section to the first byte of
735 the data making up the macro information list for the compilation
737 It is relocatable in a relocatable object file, and
738 relocated in an executable or shared object. In the 32\dash bit
739 DWARF format, this offset is a 4\dash byte unsigned value;
740 in the 64\dash bit DWARF format, it is an 8\dash byte unsigned value
741 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
743 \item \livelink{chap:rangelistptr}{rangelistptr} \\
745 \addtoindexx{section offset!in class rangelistptr value}
746 offset into the \addtoindex{.debug\_ranges} section
747 (\livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}).
749 offset from the beginning of the
750 \addtoindex{.debug\_ranges} section
751 to the beginning of the non\dash contiguous address ranges
752 information for the referencing entity.
754 a relocatable object file, and relocated in an executable or
755 shared object. In the 32\dash bit DWARF format, this offset
756 is a 4\dash byte unsigned value; in the 64\dash bit DWARF
757 format, it is an 8\dash byte unsigned value (see Section
758 \refersec{datarep:32bitand64bitdwarfformats}).
761 \textit{Because classes \livelink{chap:lineptr}{lineptr}, \livelink{chap:loclistptr}{loclistptr}, \livelink{chap:macptr}{macptr} and \livelink{chap:rangelistptr}{rangelistptr}
762 share a common representation, it is not possible for an
763 attribute to allow more than one of these classes}
768 There are three types of reference.
771 \addtoindexx{reference class}
772 first type of reference can identify any debugging
773 information entry within the containing unit.
776 \addtoindexx{section offset!in class reference value}
777 offset from the first byte of the compilation
778 header for the compilation unit containing the reference. There
779 are five forms for this type of reference. There are fixed
780 length forms for one, two, four and eight byte offsets
781 (respectively, \livetarg{chap:DWFORMref1}{DW\-\_FORM\-\_ref1},
782 \livetarg{chap:DWFORMref2}{DW\-\_FORM\-\_ref2},
783 \livetarg{chap:DWFORMref4}{DW\-\_FORM\-\_ref4},
784 and \livetarg{chap:DWFORMref8}{DW\-\_FORM\-\_ref8}).
785 There is also an unsigned variable
786 length offset encoded form that uses unsigned LEB128 numbers
787 (\livetarg{chap:DWFORMrefudata}{DW\-\_FORM\-\_ref\-\_udata}).
788 Because this type of reference is within
789 the containing compilation unit no relocation of the value
792 The second type of reference can identify any debugging
793 information entry within a
794 \addtoindex{.debug\_info} section; in particular,
795 it may refer to an entry in a different compilation unit
796 from the unit containing the reference, and may refer to an
797 entry in a different shared object. This type of reference
798 (\livetarg{chap:DWFORMrefaddr}{DW\-\_FORM\-\_ref\-\_addr}) is an offset from the beginning of the
799 \addtoindex{.debug\_info}
800 section of the target executable or shared object;
801 it is relocatable in a relocatable object file and frequently
802 relocated in an executable file or shared object. For
803 references from one shared object or static executable file
804 to another, the relocation and identification of the target
805 object must be performed by the consumer. In the 32\dash bit DWARF
806 format, this offset is a 4\dash byte unsigned value;
807 in the 64\dash bit DWARF format, it is an 8\dash byte
809 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
811 A debugging information entry that may be referenced by
812 another compilation unit using \livelink{chap:DWFORMrefaddr}{DW\-\_FORM\-\_ref\-\_addr} must have a
813 global symbolic name.
815 For a reference from one executable or shared object to
816 another, the reference is resolved by the debugger to identify
817 the shared object or executable and the offset into that
818 object’s \addtoindex{.debug\_info}
819 section in the same fashion as the run
820 time loader, either when the debug information is first read,
821 or when the reference is used.
823 The third type of reference can identify any debugging
824 information type entry that has been placed in its own
825 \addtoindex{type unit}. This type of
826 reference (\livetarg{chap:DWFORMrefsig8}{DW\-\_FORM\-\_ref\-\_sig8}) is the
827 \addtoindexx{type signature}
828 64\dash bit type signature
829 (see Section \refersec{datarep:typesignaturecomputation})
833 The use of compilation unit relative references will reduce the
834 number of link\dash time relocations and so speed up linking. The
835 use of the second and third type of reference allows for the
836 sharing of information, such as types, across compilation
839 A reference to any kind of compilation unit identifies the
840 debugging information entry for that unit, not the preceding
844 A string is a sequence of contiguous non\dash null bytes followed by
846 \addtoindexx{string class}
847 A string may be represented immediately in the
848 debugging information entry itself
849 (\livetarg{chap:DWFORMstring}{DW\-\_FORM\-\_string}), or may
851 \addtoindexx{section offset!in class string value}
852 offset into a string table contained in
853 the \addtoindex{.debug\_str} section of the object file
854 (\livetarg{chap:DWFORMstrp}{DW\-\_FORM\-\_strp}). In
855 the 32\dash bit DWARF format, the representation of a
856 \livelink{chap:DWFORMstrp}{DW\-\_FORM\-\_strp}
857 value is a 4\dash byte unsigned offset; in the 64\dash bit DWARF format,
858 it is an 8\dash byte unsigned offset
859 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
861 If the \livelink{chap:DWATuseUTF8}{DW\-\_AT\-\_use\-\_UTF8} attribute is specified for the
862 compilation unit entry, string values are encoded using the
863 UTF\dash 8 (Unicode Transformation Format\dash 8) from the Universal
864 Character Set standard (ISO/IEC 10646\dash 1:1993). Otherwise,
865 the string representation is unspecified.
867 The Unicode Standard Version 3 is fully compatible with
868 ISO/IEC 10646\dash 1:1993. It contains all the same characters
869 and encoding points as ISO/IEC 10646, as well as additional
870 information about the characters and their use.
872 Earlier versions of DWARF did not specify the representation
873 of strings; for compatibility, this version also does
874 not. However, the UTF\dash 8 representation is strongly recommended.
878 In no case does an attribute use
879 \addtoindexx{rangelistptr class}
881 \addtoindexx{loclistptr class}
883 \addtoindexx{lineptr class}
885 \addtoindexx{macptr class}
886 classes \livelink{chap:lineptr}{lineptr},
887 \livelink{chap:loclistptr}{loclistptr}, \livelink{chap:macptr}{macptr} or \livelink{chap:rangelistptr}{rangelistptr} to point into either the
888 \addtoindex{.debug\_info} or \addtoindex{.debug\_str} section.
890 The form encodings are listed in
891 Table \refersec{tab:attributeformencodings}.
894 \setlength{\extrarowheight}{0.1cm}
895 \begin{longtable}{l|l}
896 \caption{Tag encodings} \label{tab:tagencodings} \\
897 \hline \\ \bfseries Tag name&\bfseries Value\\ \hline
899 \bfseries Tag name&\bfseries Value \\ \hline
901 \hline \emph{Continued on next page}
905 \livelink{chap:DWTAGarraytype}{DW\-\_TAG\-\_array\-\_type} &0x01 \\
906 \livelink{chap:DWTAGclasstype}{DW\-\_TAG\-\_class\-\_type}&0x02 \\
907 \livelink{chap:DWTAGentrypoint}{DW\-\_TAG\-\_entry\-\_point}&0x03 \\
908 \livelink{chap:DWTAGenumerationtype}{DW\-\_TAG\-\_enumeration\-\_type}&0x04 \\
909 \livelink{chap:DWTAGformalparameter}{DW\-\_TAG\-\_formal\-\_parameter}&0x05 \\
910 \livelink{chap:DWTAGimporteddeclaration}{DW\-\_TAG\-\_imported\-\_declaration}&0x08 \\
911 \livelink{chap:DWTAGlabel}{DW\-\_TAG\-\_label}&0x0a \\
912 \livelink{chap:DWTAGlexicalblock}{DW\-\_TAG\-\_lexical\-\_block}&0x0b \\
913 \livelink{chap:DWTAGmember}{DW\-\_TAG\-\_member}&0x0d \\
914 \livelink{chap:DWTAGpointertype}{DW\-\_TAG\-\_pointer\-\_type}&0x0f \\
915 \livelink{chap:DWTAGreferencetype}{DW\-\_TAG\-\_reference\-\_type}&0x10 \\
916 \livelink{chap:DWTAGcompileunit}{DW\-\_TAG\-\_compile\-\_unit}&0x11 \\
917 \livelink{chap:DWTAGstringtype}{DW\-\_TAG\-\_string\-\_type}&0x12 \\
918 \livelink{chap:DWTAGstructuretype}{DW\-\_TAG\-\_structure\-\_type}&0x13 \\
919 \livelink{chap:DWTAGsubroutinetype}{DW\-\_TAG\-\_subroutine\-\_type}&0x15 \\
920 \livelink{chap:DWTAGtypedef}{DW\-\_TAG\-\_typedef}&0x16 \\
921 \livelink{chap:DWTAGuniontype}{DW\-\_TAG\-\_union\-\_type}&0x17 \\
922 \livelink{chap:DWTAGunspecifiedparameters}{DW\-\_TAG\-\_unspecified\-\_parameters}&0x18 \\
923 \livelink{chap:DWTAGvariant}{DW\-\_TAG\-\_variant}&0x19 \\
924 \livelink{chap:DWTAGcommonblock}{DW\-\_TAG\-\_common\-\_block}&0x1a \\
925 \livelink{chap:DWTAGcommoninclusion}{DW\-\_TAG\-\_common\-\_inclusion}&0x1b \\
926 \livelink{chap:DWTAGinheritance}{DW\-\_TAG\-\_inheritance}&0x1c \\
927 \livelink{chap:DWTAGinlinedsubroutine}{DW\-\_TAG\-\_inlined\-\_subroutine}&0x1d \\
928 \livelink{chap:DWTAGmodule}{DW\-\_TAG\-\_module}&0x1e \\
929 \livelink{chap:DWTAGptrtomembertype}{DW\-\_TAG\-\_ptr\-\_to\-\_member\-\_type}&0x1f \\
930 \livelink{chap:DWTAGsettype}{DW\-\_TAG\-\_set\-\_type}&0x20 \\
931 \livelink{chap:DWTAGsubrangetype}{DW\-\_TAG\-\_subrange\-\_type}&0x21 \\
932 \livelink{chap:DWTAGwithstmt}{DW\-\_TAG\-\_with\-\_stmt}&0x22 \\
933 \livelink{chap:DWTAGaccessdeclaration}{DW\-\_TAG\-\_access\-\_declaration}&0x23 \\
934 \livelink{chap:DWTAGbasetype}{DW\-\_TAG\-\_base\-\_type}&0x24 \\
935 \livelink{chap:DWTAGcatchblock}{DW\-\_TAG\-\_catch\-\_block}&0x25 \\
936 \livelink{chap:DWTAGconsttype}{DW\-\_TAG\-\_const\-\_type}&0x26 \\
937 \livelink{chap:DWTAGconstant}{DW\-\_TAG\-\_constant}&0x27 \\
938 \livelink{chap:DWTAGenumerator}{DW\-\_TAG\-\_enumerator}&0x28 \\
939 \livelink{chap:DWTAGfiletype}{DW\-\_TAG\-\_file\-\_type}&0x29 \\
940 \livelink{chap:DWTAGfriend}{DW\-\_TAG\-\_friend}&0x2a \\
941 \livelink{chap:DWTAGnamelist}{DW\-\_TAG\-\_namelist}&0x2b \\
942 \livelink{chap:DWTAGnamelistitem}{DW\-\_TAG\-\_namelist\-\_item}&0x2c \\
943 \livelink{chap:DWTAGpackedtype}{DW\-\_TAG\-\_packed\-\_type}&0x2d \\
944 \livelink{chap:DWTAGsubprogram}{DW\-\_TAG\-\_subprogram}&0x2e \\
945 \livelink{chap:DWTAGtemplatetypeparameter}{DW\-\_TAG\-\_template\-\_type\-\_parameter}&0x2f \\
946 \livelink{chap:DWTAGtemplatevalueparameter}{DW\-\_TAG\-\_template\-\_value\-\_parameter}&0x30 \\
947 \livelink{chap:DWTAGthrowntype}{DW\-\_TAG\-\_thrown\-\_type}&0x31 \\
948 \livelink{chap:DWTAGtryblock}{DW\-\_TAG\-\_try\-\_block}&0x32 \\
949 \livelink{chap:DWTAGvariantpart}{DW\-\_TAG\-\_variant\-\_part}&0x33 \\
950 \livelink{chap:DWTAGvariable}{DW\-\_TAG\-\_variable}&0x34 \\
951 \livelink{chap:DWTAGvolatiletype}{DW\-\_TAG\-\_volatile\-\_type}&0x35 \\
952 \livelink{chap:DWTAGdwarfprocedure}{DW\-\_TAG\-\_dwarf\-\_procedure}&0x36 \\
953 \livelink{chap:DWTAGrestricttype}{DW\-\_TAG\-\_restrict\-\_type}&0x37 \\
954 \livelink{chap:DWTAGinterfacetype}{DW\-\_TAG\-\_interface\-\_type}&0x38 \\
955 \livelink{chap:DWTAGnamespace}{DW\-\_TAG\-\_namespace}&0x39 \\
956 \livelink{chap:DWTAGimportedmodule}{DW\-\_TAG\-\_imported\-\_module}&0x3a \\
957 \livelink{chap:DWTAGunspecifiedtype}{DW\-\_TAG\-\_unspecified\-\_type}&0x3b \\
958 \livelink{chap:DWTAGpartialunit}{DW\-\_TAG\-\_partial\-\_unit}&0x3c \\
959 \livelink{chap:DWTAGimportedunit}{DW\-\_TAG\-\_imported\-\_unit}&0x3d \\
960 \livelink{chap:DWTAGcondition}{DW\-\_TAG\-\_condition}&0x3f \\
961 \livelink{chap:DWTAGsharedtype}{DW\-\_TAG\-\_shared\-\_type}&0x40 \\
962 \livelink{chap:DWTAGtypeunit}{DW\-\_TAG\-\_type\-\_unit} \ddag &0x41 \\
963 \livelink{chap:DWTAGrvaluereferencetype}{DW\-\_TAG\-\_rvalue\-\_reference\-\_type} \ddag &0x42 \\
964 \livelink{chap:DWTAGtemplatealias}{DW\-\_TAG\-\_template\-\_alias} \ddag &0x43 \\
965 \livelink{chap:DWTAGlouser}{DW\-\_TAG\-\_lo\-\_user}&0x4080 \\
966 \livelink{chap:DWTAGhiuser}{DW\-\_TAG\-\_hi\-\_user}&0xffff \\
968 \ddag TAG new in \addtoindex{DWARF Version 4}
974 \setlength{\extrarowheight}{0.1cm}
975 \caption{Child determination encodings}
976 \label{tab:childdeterminationencodings}
977 \begin{tabular}{l|l} \hline
978 Child determination name& Value\\ \hline
979 \livelink{chap:DWCHILDRENno}{DW\-\_CHILDREN\-\_no}&0x00 \\
980 \livelink{chap:DWCHILDRENyes}{DW\-\_CHILDREN\-\_yes}&0x01 \\ \hline
986 \setlength{\extrarowheight}{0.1cm}
987 \begin{longtable}{l|l|l}
988 \caption{Attribute encodings} \label{tab:attributeencodings} \addtoindexx{attribute encodings} \\
989 \hline \\ \bfseries Attribute name&\bfseries Value &\bfseries Classes \\ \hline
991 \bfseries Attribute name&\bfseries Value &\bfseries Classes\\ \hline
993 \hline \emph{Continued on next page}
997 \livelink{chap:DWATsibling}{DW\-\_AT\-\_sibling}&0x01&reference
998 \addtoindexx{sibling attribute!encoding} \\
999 \livelink{chap:DWATlocation}{DW\-\_AT\-\_location}&0x02&\livelink{chap:exprloc}{exprloc},
1000 \livelink{chap:loclistptr}{loclistptr}\addtoindex{location attribute!encoding} \\
1001 \livelink{chap:DWATname}{DW\-\_AT\-\_name}&0x03&string
1002 \addtoindexx{name attribute!encoding} \\
1003 \livelink{chap:DWATordering}{DW\-\_AT\-\_ordering}&0x09&constant
1004 \addtoindexx{ordering attribute!encoding} \\
1005 \livelink{chap:DWATbytesize}{DW\-\_AT\-\_byte\-\_size}&0x0b&constant, \livelink{chap:exprloc}{exprloc},
1006 reference \addtoindexx{byte size attribute!encoding} \\
1007 \livelink{chap:DWATbitoffset}{DW\-\_AT\-\_bit\-\_offset}&0x0c&constant,
1008 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{bit offset attribute!encoding} \\
1009 \livelink{chap:DWATbitsize}{DW\-\_AT\-\_bit\-\_size}&0x0d&constant,
1010 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{bit size attribute!encoding} \\
1011 \livelink{chap:DWATstmtlist}{DW\-\_AT\-\_stmt\-\_list}&0x10&\livelink{chap:lineptr}{lineptr}
1012 \addtoindex{statement list attribute!encoding} \\
1013 \livelink{chap:DWATlowpc}{DW\-\_AT\-\_low\-\_pc}&0x11&address
1014 \addtoindexx{low PC attribute!encoding} \\
1015 \livelink{chap:DWAThighpc}{DW\-\_AT\-\_high\-\_pc}&0x12&address, constant
1016 \addtoindexx{high PC attribute!encoding} \\
1017 \livelink{chap:DWATlanguage}{DW\-\_AT\-\_language}&0x13&constant
1018 \addtoindexx{language attribute!encoding} \\
1019 \livelink{chap:DWATdiscr}{DW\-\_AT\-\_discr}&0x15&reference
1020 \addtoindexx{discriminant attribute!encoding} \\
1021 \livelink{chap:DWATdiscrvalue}{DW\-\_AT\-\_discr\-\_value}&0x16&constant
1022 \addtoindexx{discriminant value attribute!encoding} \\
1023 \livelink{chap:DWATvisibility}{DW\-\_AT\-\_visibility}&0x17&constant
1024 \addtoindexx{visibility attribute!encoding} \\
1025 \livelink{chap:DWATimport}{DW\-\_AT\-\_import}&0x18&reference
1026 \addtoindexx{import attribute!encoding} \\
1027 \livelink{chap:DWATstringlength}{DW\-\_AT\-\_string\-\_length}&0x19&\livelink{chap:exprloc}{exprloc},
1028 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{string length attribute!encoding} \\
1029 \livelink{chap:DWATcommonreference}{DW\-\_AT\-\_common\-\_reference}&0x1a&reference
1030 \addtoindexx{common reference attribute!encoding} \\
1031 \livelink{chap:DWATcompdir}{DW\-\_AT\-\_comp\-\_dir}&0x1b&string
1032 \addtoindexx{compilation directory attribute!encoding} \\
1033 \livelink{chap:DWATconstvalue}{DW\-\_AT\-\_const\-\_value}&0x1c&\livelink{chap:block}{block}, constant, string
1034 \addtoindexx{constant value attribute!encoding} \\
1035 \livelink{chap:DWATcontainingtype}{DW\-\_AT\-\_containing\-\_type}&0x1d&reference
1036 \addtoindexx{containing type attribute!encoding} \\
1037 \livelink{chap:DWATdefaultvalue}{DW\-\_AT\-\_default\-\_value}&0x1e&reference
1038 \addtoindexx{default value attribute!encoding} \\
1039 \livelink{chap:DWATinline}{DW\-\_AT\-\_inline}&0x20&constant
1040 \addtoindexx{inline attribute!encoding} \\
1041 \livelink{chap:DWATisoptional}{DW\-\_AT\-\_is\-\_optional}&0x21&\livelink{chap:flag}{flag}
1042 \addtoindexx{is optional attribute!encoding} \\
1043 \livelink{chap:DWATlowerbound}{DW\-\_AT\-\_lower\-\_bound}&0x22&constant,
1044 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{lower bound attribute!encoding} \\
1045 \livelink{chap:DWATproducer}{DW\-\_AT\-\_producer}&0x25&string \addtoindexx{producer attribute!encoding} \\
1046 \livelink{chap:DWATprototyped}{DW\-\_AT\-\_prototyped}&0x27&\livelink{chap:flag}{flag}
1047 \addtoindexx{prototyped attribute!encoding} \\
1048 \livelink{chap:DWATreturnaddr}{DW\-\_AT\-\_return\-\_addr}&0x2a&\livelink{chap:exprloc}{exprloc},
1049 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{return address attribute!encoding} \\
1050 % FIXME: lower case , not Constant
1051 \livelink{chap:DWATstartscope}{DW\-\_AT\-\_start\-\_scope}&0x2c&Constant,
1052 \livelink{chap:rangelistptr}{rangelistptr} \addtoindexx{start scope attribute!encoding} \\
1053 \livelink{chap:DWATbitstride}{DW\-\_AT\-\_bit\-\_stride}&0x2e&constant,
1054 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{bit stride attribute!encoding} \\
1055 \livelink{chap:DWATupperbound}{DW\-\_AT\-\_upper\-\_bound}&0x2f&constant,
1056 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{upper bound attribute!encoding} \\
1057 \livelink{chap:DWATabstractorigin}{DW\-\_AT\-\_abstract\-\_origin}&0x31&reference
1058 \addtoindexx{abstract origin attribute!encoding} \\
1059 \livelink{chap:DWATaccessibility}{DW\-\_AT\-\_accessibility}&0x32&constant
1060 \addtoindexx{accessibility attribute!encoding} \\
1061 \livelink{chap:DWATaddressclass}{DW\-\_AT\-\_address\-\_class}&0x33&constant
1062 \addtoindexx{address class atribute!encoding} \\
1063 \livelink{chap:DWATartificial}{DW\-\_AT\-\_artificial}&0x34&\livelink{chap:flag}{flag}
1064 \addtoindexx{artificial attribute!encoding} \\
1065 \livelink{chap:DWATbasetypes}{DW\-\_AT\-\_base\-\_types}&0x35&reference
1066 \addtoindexx{base types attribute!encoding} \\
1067 \livelink{chap:DWATcallingconvention}{DW\-\_AT\-\_calling\-\_convention}&0x36&constant
1068 \addtoindexx{calling convention attribute!encoding} \\
1069 \livelink{chap:DWATcount}{DW\-\_AT\-\_count}&0x37&constant, \livelink{chap:exprloc}{exprloc}, reference
1070 \addtoindexx{count attribute!encoding} \\
1071 \livelink{chap:DWATdatamemberlocation}{DW\-\_AT\-\_data\-\_member\-\_location}&0x38&constant,
1072 \livelink{chap:exprloc}{exprloc}, \livelink{chap:loclistptr}{loclistptr}
1073 \addtoindexx{data member attribute!encoding} \\
1074 \livelink{chap:DWATdeclcolumn}{DW\-\_AT\-\_decl\-\_column}&0x39&constant
1075 \addtoindexx{declaration column attribute!encoding} \\
1076 \livelink{chap:DWATdeclfile}{DW\-\_AT\-\_decl\-\_file}&0x3a&constant
1077 \addtoindexx{declaration file attribute!encoding} \\
1078 \livelink{chap:DWATdeclline}{DW\-\_AT\-\_decl\-\_line}&0x3b&constant
1079 \addtoindexx{declaration line attribute!encoding} \\
1080 \livelink{chap:DWATdeclaration}{DW\-\_AT\-\_declaration}&0x3c&\livelink{chap:flag}{flag}
1081 \addtoindexx{declaration attribute!encoding} \\
1082 \livelink{chap:DWATdiscrlist}{DW\-\_AT\-\_discr\-\_list}&0x3d&\livelink{chap:block}{block}
1083 \addtoindexx{discriminant list attribute!encoding} \\
1084 \livelink{chap:DWATencoding}{DW\-\_AT\-\_encoding}&0x3e&constant
1085 \addtoindexx{encoding attribute!encoding} \\
1086 \livelink{chap:DWATexternal}{DW\-\_AT\-\_external}&0x3f&\livelink{chap:flag}{flag}
1087 \addtoindexx{external attribute!encoding} \\
1088 \livelink{chap:DWATframebase}{DW\-\_AT\-\_frame\-\_base}&0x40&\livelink{chap:exprloc}{exprloc},
1089 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{frame base attribute!encoding} \\
1090 \livelink{chap:DWATfriend}{DW\-\_AT\-\_friend}&0x41&reference
1091 \addtoindexx{friend attribute!encoding} \\
1092 \livelink{chap:DWATidentifiercase}{DW\-\_AT\-\_identifier\-\_case}&0x42&constant
1093 \addtoindexx{identifier case attribute!encoding} \\
1094 \livelink{chap:DWATmacroinfo}{DW\-\_AT\-\_macro\-\_info}&0x43&\livelink{chap:macptr}{macptr}
1095 \addtoindexx{macro information attribute!encoding} \\
1096 \livelink{chap:DWATnamelistitem}{DW\-\_AT\-\_namelist\-\_item}&0x44&reference
1097 \addtoindexx{name list item attribute!encoding} \\
1098 \livelink{chap:DWATpriority}{DW\-\_AT\-\_priority}&0x45&reference
1099 \addtoindexx{priority attribute!encoding} \\
1100 \livelink{chap:DWATsegment}{DW\-\_AT\-\_segment}&0x46&\livelink{chap:exprloc}{exprloc},
1101 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{segment attribute!encoding} \\
1102 \livelink{chap:DWATspecification}{DW\-\_AT\-\_specification}&0x47&reference
1103 \addtoindexx{specification attribute!encoding} \\
1104 \livelink{chap:DWATstaticlink}{DW\-\_AT\-\_static\-\_link}&0x48&\livelink{chap:exprloc}{exprloc},
1105 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{static link attribute!encoding} \\
1106 \livelink{chap:DWATtype}{DW\-\_AT\-\_type}&0x49&reference
1107 \addtoindexx{type attribute!encoding} \\
1108 \livelink{chap:DWATuselocation}{DW\-\_AT\-\_use\-\_location}&0x4a&\livelink{chap:exprloc}{exprloc},
1109 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{location list attribute!encoding} \\
1110 \livelink{chap:DWATvariableparameter}{DW\-\_AT\-\_variable\-\_parameter}&0x4b&\livelink{chap:flag}{flag}
1111 \addtoindexx{variable parameter attribute!encoding} \\
1112 \livelink{chap:DWATvirtuality}{DW\-\_AT\-\_virtuality}&0x4c&constant
1113 \addtoindexx{virtuality attribute!encoding} \\
1114 \livelink{chap:DWATvtableelemlocation}{DW\-\_AT\-\_vtable\-\_elem\-\_location}&0x4d&\livelink{chap:exprloc}{exprloc},
1115 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{vtable element location attribute!encoding} \\
1117 \livelink{chap:DWATallocated}{DW\-\_AT\-\_allocated}&0x4e&constant, \livelink{chap:exprloc}{exprloc},
1118 reference \addtoindexx{allocated attribute!encoding} \\
1119 \livelink{chap:DWATassociated}{DW\-\_AT\-\_associated}&0x4f&constant, \livelink{chap:exprloc}{exprloc},
1120 reference \addtoindexx{associated attribute!encoding} \\
1121 \livelink{chap:DWATdatalocation}{DW\-\_AT\-\_data\-\_location}&0x50&\livelink{chap:exprloc}{exprloc}
1122 \addtoindexx{data location attribute!encoding} \\
1123 \livelink{chap:DWATbytestride}{DW\-\_AT\-\_byte\-\_stride}&0x51&constant, \livelink{chap:exprloc}{exprloc},
1124 reference \addtoindexx{byte stride attribute!encoding} \\
1125 \livelink{chap:DWATentrypc}{DW\-\_AT\-\_entry\-\_pc}&0x52&address
1126 \addtoindexx{entry pc attribute!encoding} \\
1127 \livelink{chap:DWATuseUTF8}{DW\-\_AT\-\_use\-\_UTF8}&0x53&\livelink{chap:flag}{flag}
1128 \addtoindexx{use UTF8 attribute!encoding} \\
1129 \livelink{chap:DWATextension}{DW\-\_AT\-\_extension}&0x54&reference
1130 \addtoindexx{extension attribute!encoding} \\
1131 \livelink{chap:DWATranges}{DW\-\_AT\-\_ranges}&0x55&\livelink{chap:rangelistptr}{rangelistptr}
1132 \addtoindexx{ranges attribute!encoding} \\
1133 \livelink{chap:DWATtrampoline}{DW\-\_AT\-\_trampoline}&0x56&address, \livelink{chap:flag}{flag},
1134 reference, string \addtoindexx{trampoline attribute!encoding} \\
1135 \livelink{chap:DWATcallcolumn}{DW\-\_AT\-\_call\-\_column}&0x57&constant
1136 \addtoindexx{call column attribute!encoding} \\
1137 \livelink{chap:DWATcallfile}{DW\-\_AT\-\_call\-\_file}&0x58&constant
1138 \addtoindexx{call file attribute!encoding} \\
1139 \livelink{chap:DWATcallline}{DW\-\_AT\-\_call\-\_line}&0x59&constant
1140 \addtoindexx{call line attribute!encoding} \\
1141 \livelink{chap:DWATdescription}{DW\-\_AT\-\_description}&0x5a&string
1142 \addtoindexx{description attribute!encoding} \\
1143 \livelink{chap:DWATbinaryscale}{DW\-\_AT\-\_binary\-\_scale}&0x5b&constant
1144 \addtoindexx{binary scale attribute!encoding} \\
1145 \livelink{chap:DWATdecimalscale}{DW\-\_AT\-\_decimal\-\_scale}&0x5c&constant
1146 \addtoindexx{decimal scale attribute!encoding} \\
1147 \livelink{chap:DWATsmall}{DW\-\_AT\-\_small} &0x5d&reference
1148 \addtoindexx{small attribute!encoding} \\
1149 \livelink{chap:DWATdecimalsign}{DW\-\_AT\-\_decimal\-\_sign}&0x5e&constant
1150 \addtoindexx{decimal scale attribute!encoding} \\
1151 \livelink{chap:DWATdigitcount}{DW\-\_AT\-\_digit\-\_count}&0x5f&constant
1152 \addtoindexx{digit count attribute!encoding} \\
1153 \livelink{chap:DWATpicturestring}{DW\-\_AT\-\_picture\-\_string}&0x60&string
1154 \addtoindexx{picture string attribute!encoding} \\
1155 \livelink{chap:DWATmutable}{DW\-\_AT\-\_mutable}&0x61&\livelink{chap:flag}{flag}
1156 \addtoindexx{mutable attribute!encoding} \\
1158 \livelink{chap:DWATthreadsscaled}{DW\-\_AT\-\_threads\-\_scaled}&0x62&\livelink{chap:flag}{flag}
1159 \addtoindexx{thread scaled attribute!encoding} \\
1160 \livelink{chap:DWATexplicit}{DW\-\_AT\-\_explicit}&0x63&\livelink{chap:flag}{flag}
1161 \addtoindexx{explicit attribute!encoding} \\
1162 \livelink{chap:DWATobjectpointer}{DW\-\_AT\-\_object\-\_pointer}&0x64&reference
1163 \addtoindexx{object pointer attribute!encoding} \\
1164 \livelink{chap:DWATendianity}{DW\-\_AT\-\_endianity}&0x65&constant
1165 \addtoindexx{endianity attribute!encoding} \\
1166 \livelink{chap:DWATelemental}{DW\-\_AT\-\_elemental}&0x66&\livelink{chap:flag}{flag}
1167 \addtoindexx{elemental attribute!encoding} \\
1168 \livelink{chap:DWATpure}{DW\-\_AT\-\_pure}&0x67&\livelink{chap:flag}{flag}
1169 \addtoindexx{pure attribute!encoding} \\
1170 \livelink{chap:DWATrecursive}{DW\-\_AT\-\_recursive}&0x68&\livelink{chap:flag}{flag}
1171 \addtoindexx{recursive attribute!encoding} \\
1172 \livelink{chap:DWATsignature}{DW\-\_AT\-\_signature} \ddag &0x69&reference
1173 \addtoindexx{signature attribute!encoding} \\
1174 \livelink{chap:DWATmainsubprogram}{DW\-\_AT\-\_main\-\_subprogram} \ddag &0x6a&\livelink{chap:flag}{flag}
1175 \addtoindexx{main subprogram attribute!encoding} \\
1176 \livelink{chap:DWATdatabitoffset}{DW\-\_AT\-\_data\-\_bit\-\_offset} \ddag &0x6b&constant
1177 \addtoindexx{data bit offset attribute!encoding} \\
1178 \livelink{chap:DWATconstexpr}{DW\-\_AT\-\_const\-\_expr} \ddag &0x6c&\livelink{chap:flag}{flag}
1179 \addtoindexx{constant expression attribute!encoding} \\
1180 \livelink{chap:DWATenumclass}{DW\-\_AT\-\_enum\-\_class} \ddag &0x6d&\livelink{chap:flag}{flag}
1181 \addtoindexx{enumeration class attribute!encoding} \\
1182 \livelink{chap:DWATlinkagename}{DW\-\_AT\-\_linkage\-\_name} \ddag &0x6e&string
1183 \addtoindexx{linkage name attribute!encoding} \\
1184 \livetarg{chap:DWATlouser}{DW\-\_AT\-\_lo\-\_user}&0x2000 & --- \addtoindexx{low user attribute encoding} \\
1185 \livetarg{chap:DWAThiuser}{DW\-\_AT\-\_hi\-\_user}&0x3fff& --- \addtoindexx{high user attribute encoding} \\
1188 \ddag Attribute new in \addtoindex{DWARF Version 4}
1192 \setlength{\extrarowheight}{0.1cm}
1193 \begin{longtable}{l|l|l}
1194 \caption{Attribute form encodings} \label{tab:attributeformencodings} \\
1195 \hline \\ \bfseries Form name&\bfseries Value &\bfseries Classes \\ \hline
1197 \bfseries Form name&\bfseries Value &\bfseries Classes\\ \hline
1199 \hline \emph{Continued on next page}
1203 \livelink{chap:DWFORMaddr}{DW\-\_FORM\-\_addr}&0x01&address \\
1204 \livelink{chap:DWFORMblock2}{DW\-\_FORM\-\_block2}&0x03&\livelink{chap:block}{block} \\
1205 \livelink{chap:DWFORMblock4}{DW\-\_FORM\-\_block4}&0x04&\livelink{chap:block}{block} \\
1206 \livelink{chap:DWFORMdata2}{DW\-\_FORM\-\_data2}&0x05&constant \\
1207 \livelink{chap:DWFORMdata4}{DW\-\_FORM\-\_data4}&0x06&constant \\
1208 \livelink{chap:DWFORMdata8}{DW\-\_FORM\-\_data8}&0x07&constant \\
1209 \livelink{chap:DWFORMstring}{DW\-\_FORM\-\_string}&0x08&string \\
1210 \livelink{chap:DWFORMblock}{DW\-\_FORM\-\_block}&0x09&\livelink{chap:block}{block} \\
1211 \livelink{chap:DWFORMblock1}{DW\-\_FORM\-\_block1}&0x0a&\livelink{chap:block}{block} \\
1212 \livelink{chap:DWFORMdata1}{DW\-\_FORM\-\_data1}&0x0b&constant \\
1213 \livelink{chap:DWFORMflag}{DW\-\_FORM\-\_flag}&0x0c&\livelink{chap:flag}{flag} \\
1214 \livelink{chap:DWFORMsdata}{DW\-\_FORM\-\_sdata}&0x0d&constant \\
1215 \livelink{chap:DWFORMstrp}{DW\-\_FORM\-\_strp}&0x0e&string \\
1216 \livelink{chap:DWFORMudata}{DW\-\_FORM\-\_udata}&0x0f&constant \\
1217 \livelink{chap:DWFORMrefaddr}{DW\-\_FORM\-\_ref\-\_addr}&0x10&reference \\
1218 \livelink{chap:DWFORMref1}{DW\-\_FORM\-\_ref1}&0x11&reference \\
1219 \livelink{chap:DWFORMref2}{DW\-\_FORM\-\_ref2}&0x12&reference \\
1220 \livelink{chap:DWFORMref4}{DW\-\_FORM\-\_ref4}&0x13&reference \\
1221 \livelink{chap:DWFORMref8}{DW\-\_FORM\-\_ref8}&0x14&reference \\
1222 \livelink{chap:DWFORMrefudata}{DW\-\_FORM\-\_ref\-\_udata}&0x15&reference \\
1223 \livelink{chap:DWFORMindirect}{DW\-\_FORM\-\_indirect}&0x16&(see Section \refersec{datarep:abbreviationstables}) \\
1224 \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} \\
1225 \livelink{chap:DWFORMexprloc}{DW\-\_FORM\-\_exprloc} \ddag &0x18&\livelink{chap:exprloc}{exprloc} \\
1226 \livelink{chap:DWFORMflagpresent}{DW\-\_FORM\-\_flag\-\_present} \ddag &0x19&\livelink{chap:flag}{flag} \\
1227 \livelink{chap:DWFORMrefsig8}{DW\-\_FORM\-\_ref\-\_sig8} \ddag &0x20&reference \\
1230 \ddag FORM new in \addtoindex{DWARF Version 4}
1233 \section{Variable Length Data}
1234 \label{datarep:variablelengthdata}
1235 \addtoindexx{variable length data|see {LEB128}}
1237 \addtoindexx{Little Endian Base 128|see{LEB128}}
1238 encoded using ``Little Endian Base 128''
1239 \addtoindexx{little-endian encoding|see{endian attribute}}
1241 \addtoindexx{LEB128}
1242 LEB128 is a scheme for encoding integers
1243 densely that exploits the assumption that most integers are
1246 This encoding is equally suitable whether the target machine
1247 architecture represents data in big\dash\ endian or little\dash endian
1248 order. It is ``little\dash endian'' only in the sense that it
1249 avoids using space to represent the ``big'' end of an
1250 unsigned integer, when the big end is all zeroes or sign
1253 Unsigned LEB128 (ULEB128) numbers are encoded as follows:
1254 \addtoindexx{LEB128!unsigned, encoding as}
1255 start at the low order end of an unsigned integer and chop
1256 it into 7\dash bit chunks. Place each chunk into the low order 7
1257 bits of a byte. Typically, several of the high order bytes
1258 will be zero; discard them. Emit the remaining bytes in a
1259 stream, starting with the low order byte; set the high order
1260 bit on each byte except the last emitted byte. The high bit
1261 of zero on the last byte indicates to the decoder that it
1262 has encountered the last byte.
1264 The integer zero is a special case, consisting of a single
1267 Table \refersec{tab:examplesofunsignedleb128encodings}
1268 gives some examples of unsigned LEB128 numbers. The
1269 0x80 in each case is the high order bit of the byte, indicating
1270 that an additional byte follows.
1273 The encoding for signed, two’s complement LEB128 (SLEB128)
1274 \addtoindexx{LEB128!signed, encoding as}
1275 numbers is similar, except that the criterion for discarding
1276 high order bytes is not whether they are zero, but whether
1277 they consist entirely of sign extension bits. Consider the
1278 32\dash bit integer -2. The three high level bytes of the number
1279 are sign extension, thus LEB128 would represent it as a single
1280 byte containing the low order 7 bits, with the high order
1281 bit cleared to indicate the end of the byte stream. Note
1282 that there is nothing within the LEB128 representation that
1283 indicates whether an encoded number is signed or unsigned. The
1284 decoder must know what type of number to expect.
1285 Table \refersec{tab:examplesofunsignedleb128encodings}
1286 gives some examples of unsigned LEB128 numbers and
1287 Table \refersec{tab:examplesofsignedleb128encodings}
1288 gives some examples of signed LEB128
1291 Appendix \refersec{app:variablelengthdataencodingdecodinginformative}
1292 \addtoindexx{LEB128!examples}
1293 gives algorithms for encoding and decoding these forms.
1297 \setlength{\extrarowheight}{0.1cm}
1298 \begin{longtable}{l|l|l}
1299 \caption{Examples of unsigned LEB128 encodings} \label{tab:examplesofunsignedleb128encodings} \\
1300 \hline \\ \bfseries Number&\bfseries First byte &\bfseries Second byte \\ \hline
1302 \bfseries Number&\bfseries First Byte &\bfseries Second byte\\ \hline
1304 \hline \emph{Continued on next page}
1310 128& 0 + 0x80 & 1 \\
1311 129& 1 + 0x80 & 1 \\
1312 130& 2 + 0x80 & 1 \\
1313 12857& 57 + 0x80 & 100 \\
1314 \addtoindex{LEB128 encoding!examples}
1321 \setlength{\extrarowheight}{0.1cm}
1322 \begin{longtable}{l|l|l}
1323 \caption{Examples of signed LEB128 encodings} \label{tab:examplesofsignedleb128encodings} \\
1324 \hline \\ \bfseries Number&\bfseries First byte &\bfseries Second byte \\ \hline
1326 \bfseries Number&\bfseries First Byte &\bfseries Second byte\\ \hline
1328 \hline \emph{Continued on next page}
1334 127& 127 + 0x80 & 0 \\
1335 -127& 1 + 0x80 & 0x7f \\
1336 128& 0 + 0x80 & 1 \\
1337 -128& 0 + 0x80 & 0x7f \\
1338 129& 1 + 0x80 & 1 \\
1339 -129& -x7f + 0x80 & 0xtc \\
1346 \section{DWARF Expressions and Location Descriptions}
1347 \label{datarep:dwarfexpressionsandlocationdescriptions}
1348 \subsection{DWARF Expressions}
1349 \label{datarep:dwarfexpressions}
1352 \addtoindexx{DWARF Expression!operator encoding}
1353 DWARF expression is stored in a \nolink{block} of contiguous
1354 bytes. The bytes form a sequence of operations. Each operation
1355 is a 1\dash byte code that identifies that operation, followed by
1356 zero or more bytes of additional data. The encodings for the
1357 operations are described in
1358 Table \refersec{tab:dwarfoperationencodings}.
1361 \setlength{\extrarowheight}{0.1cm}
1362 \begin{longtable}{l|l|l|l}
1363 \caption{DWARF operation encodings} \label{tab:dwarfoperationencodings} \\
1364 \hline \\ & &\bfseries No. of &\\
1365 \bfseries Operation&\bfseries Code &\bfseries Operands &\bfseries Notes\\ \hline
1367 & &\bfseries No. of &\\
1368 \bfseries Operation&\bfseries Code &\bfseries Operands &\bfseries Notes\\ \hline
1370 \hline \emph{Continued on next page}
1375 \livelink{chap:DWOPaddr}{DW\-\_OP\-\_addr}&0x03&1 & constant address \\
1376 & & &(size target specific) \\
1378 \livelink{chap:DWOPderef}{DW\-\_OP\-\_deref}&0x06&0 & \\
1381 \livelink{chap:DWOPconst1u}{DW\-\_OP\-\_const1u}&0x08&1&1\dash byte constant \\
1382 \livelink{chap:DWOPconst1s}{DW\-\_OP\-\_const1s}&0x09&1&1\dash byte constant \\
1383 \livelink{chap:DWOPconst2u}{DW\-\_OP\-\_const2u}&0x0a&1&2\dash byte constant \\
1384 \livelink{chap:DWOPconst2s}{DW\-\_OP\-\_const2s}&0x0b&1&2\dash byte constant \\
1385 \livelink{chap:DWOPconst4u}{DW\-\_OP\-\_const4u}&0x0c&1&4\dash byte constant \\
1386 \livelink{chap:DWOPconst4s}{DW\-\_OP\-\_const4s}&0x0d&1&4\dash byte constant \\
1387 \livelink{chap:DWOPconst8u}{DW\-\_OP\-\_const8u}&0x0e&1&8\dash byte constant \\
1388 \livelink{chap:DWOPconst8s}{DW\-\_OP\-\_const8s}&0x0f&1&8\dash byte constant \\
1389 \livelink{chap:DWOPconstu}{DW\-\_OP\-\_constu}&0x10&1&ULEB128 constant \\
1390 \livelink{chap:DWOPconsts}{DW\-\_OP\-\_consts}&0x11&1&SLEB128 constant \\
1391 \livelink{chap:DWOPdup}{DW\-\_OP\-\_dup}&0x12&0 & \\
1392 \livelink{chap:DWOPdrop}{DW\-\_OP\-\_drop}&0x13&0 & \\
1393 \livelink{chap:DWOPover}{DW\-\_OP\-\_over}&0x14&0 & \\
1394 \livelink{chap:DWOPpick}{DW\-\_OP\-\_pick}&0x15&1&1\dash byte stack index \\
1395 \livelink{chap:DWOPswap}{DW\-\_OP\-\_swap}&0x16&0 & \\
1396 \livelink{chap:DWOProt}{DW\-\_OP\-\_rot}&0x17&0 & \\
1397 \livelink{chap:DWOPxderef}{DW\-\_OP\-\_xderef}&0x18&0 & \\
1398 \livelink{chap:DWOPabs}{DW\-\_OP\-\_abs}&0x19&0 & \\
1399 \livelink{chap:DWOPand}{DW\-\_OP\-\_and}&0x1a&0 & \\
1400 \livelink{chap:DWOPdiv}{DW\-\_OP\-\_div}&0x1b&0 & \\
1404 \livelink{chap:DWOPminus}{DW\-\_OP\-\_minus}&0x1c&0 & \\
1405 \livelink{chap:DWOPmod}{DW\-\_OP\-\_mod}&0x1d&0 & \\
1406 \livelink{chap:DWOPmul}{DW\-\_OP\-\_mul}&0x1e&0 & \\
1407 \livelink{chap:DWOPneg}{DW\-\_OP\-\_neg}&0x1f&0 & \\
1408 \livelink{chap:DWOPnot}{DW\-\_OP\-\_not}&0x20&0 & \\
1409 \livelink{chap:DWOPor}{DW\-\_OP\-\_or}&0x21&0 & \\
1410 \livelink{chap:DWOPplus}{DW\-\_OP\-\_plus}&0x22&0 & \\
1411 \livelink{chap:DWOPplusuconst}{DW\-\_OP\-\_plus\-\_uconst}&0x23&1&ULEB128 addend \\
1412 \livelink{chap:DWOPshl}{DW\-\_OP\-\_shl}&0x24&0 & \\
1413 \livelink{chap:DWOPshr}{DW\-\_OP\-\_shr}&0x25&0 & \\
1414 \livelink{chap:DWOPshra}{DW\-\_OP\-\_shra}&0x26&0 & \\
1415 \livelink{chap:DWOPxor}{DW\-\_OP\-\_xor}&0x27&0 & \\
1416 \livelink{chap:DWOPskip}{DW\-\_OP\-\_skip}&0x2f&1&signed 2\dash byte constant \\
1417 \livelink{chap:DWOPbra}{DW\-\_OP\-\_bra}&0x28&1 & signed 2\dash byte constant \\
1418 \livelink{chap:DWOPeq}{DW\-\_OP\-\_eq}&0x29&0 & \\
1419 \livelink{chap:DWOPge}{DW\-\_OP\-\_ge}&0x2a&0 & \\
1420 \livelink{chap:DWOPgt}{DW\-\_OP\-\_gt}&0x2b&0 & \\
1421 \livelink{chap:DWOPle}{DW\-\_OP\-\_le}&0x2c&0 & \\
1422 \livelink{chap:DWOPlt}{DW\-\_OP\-\_lt}&0x2d&0 & \\
1423 \livelink{chap:DWOPne}{DW\-\_OP\-\_ne}&0x2e&0 & \\ \hline
1427 \livelink{chap:DWOPlit0}{DW\-\_OP\-\_lit0}&0x30 & 0 & \\
1429 \livelink{chap:DWOPlit1}{DW\-\_OP\-\_lit1}&0x31 & 0& literals 0 .. 31 = \\
1430 \ldots & & & (\livelink{chap:DWOPlit0}{DW\-\_OP\-\_lit0} + literal) \\
1431 \livelink{chap:DWOPlit31}{DW\-\_OP\-\_lit31}&0x4f & 0 & \\ \hline
1433 \livelink{chap:DWOPreg0}{DW\-\_OP\-\_reg0} & 0x50 & 0 & \\
1434 \livelink{chap:DWOPreg1}{DW\-\_OP\-\_reg1} & 0x51 & 0® 0 .. 31 = \\
1435 \ldots & & & (\livelink{chap:DWOPreg0}{DW\-\_OP\-\_reg0} + regnum) \\
1436 \livelink{chap:DWOPreg31}{DW\-\_OP\-\_reg31} & 0x6f & 0 & \\ \hline
1438 \livelink{chap:DWOPbreg0}{DW\-\_OP\-\_breg0} & 0x70 &1 & SLEB128 offset \\
1439 \livelink{chap:DWOPbreg1}{DW\-\_OP\-\_breg1} & 0x71 & 1 &base register 0 .. 31 = \\
1440 ... & & &(\livelink{chap:DWOPbreg0}{DW\-\_OP\-\_breg0} + regnum) \\
1441 \livelink{chap:DWOPbreg31}{DW\-\_OP\-\_breg31} & 0x8f & 1 & \\ \hline
1443 \livelink{chap:DWOPregx}{DW\-\_OP\-\_regx} & 0x90 &1&ULEB128 register \\
1444 \livelink{chap:DWOPfbreg}{DW\-\_OP\-\_fbreg} & 0x91&1&SLEB128 offset \\
1445 \livelink{chap:DWOPbregx}{DW\-\_OP\-\_bregx} & 0x92&2 &ULEB128 register followed \\
1446 & & & by SLEB128 offset \\
1447 \livelink{chap:DWOPpiece}{DW\-\_OP\-\_piece} & 0x93 &1& ULEB128 size of piece addressed \\
1448 \livelink{chap:DWOPderefsize}{DW\-\_OP\-\_deref\-\_size} & 0x94 &1& 1-byte size of data retrieved \\
1449 \livelink{chap:DWOPxderefsize}{DW\-\_OP\-\_xderef\-\_size} & 0x95&1&1-byte size of data retrieved \\
1450 \livelink{chap:DWOPnop}{DW\-\_OP\-\_nop} & 0x96 &0& \\
1453 \livelink{chap:DWOPpushobjectaddress}{DW\-\_OP\-\_push\-\_object\-\_address}&0x97&0 & \\
1454 \livelink{chap:DWOPcall2}{DW\-\_OP\-\_call2}&0x98&1& 2\dash byte offset of DIE \\
1455 \livelink{chap:DWOPcall4}{DW\-\_OP\-\_call4}&0x99&1& 4\dash byte offset of DIE \\
1456 \livelink{chap:DWOPcallref}{DW\-\_OP\-\_call\-\_ref}&0x9a&1& 4\dash\ or 8\dash byte\\
1457 &&& offset of DIE \\
1458 \livelink{chap:DWOPformtlsaddress}{DW\-\_OP\-\_form\-\_tls\-\_address}&0x9b &0& \\
1459 \livelink{chap:DWOPcallframecfa}{DW\-\_OP\-\_call\-\_frame\-\_cfa} &0x9c &0& \\
1460 \livelink{chap:DWOPbitpiece}{DW\-\_OP\-\_bit\-\_piece}&0x9d &2&ULEB128 size followed by \\
1462 \livelink{chap:DWOPimplicitvalue}{DW\-\_OP\-\_implicit\-\_value}&0x9e &2&ULEB128 size followed by \\
1463 &&&\nolink{block} of that size\\
1464 \livelink{chap:DWOPstackvalue}{DW\-\_OP\-\_stack\-\_value} &0x9f &0& \\
1465 \livetarg{chap:DWOPlouser}{DW\-\_OP\-\_lo\-\_user} &0xe0 && \\
1466 \livetarg{chap:DWOPhiuser}{DW\-\_OP\-\_hi\-\_user} &0xff && \\
1472 \subsection{Location Descriptions}
1473 \label{datarep:locationdescriptions}
1475 A location description is used to compute the
1476 location of a variable or other entity.
1478 \subsection{Location Lists}
1479 \label{datarep:locationlists}
1481 Each entry in a \addtoindex{location list} is either a location list entry,
1482 a base address selection entry, or an
1483 \addtoindex{end of list entry!in location list}
1486 A \addtoindex{location list} entry consists of two address offsets followed
1487 by a 2\dash byte length, followed by a block of contiguous bytes
1488 that contains a DWARF location description. The length
1489 specifies the number of bytes in that block. The two offsets
1490 are the same size as an address on the target machine.
1492 A base address selection entry and an
1493 \addtoindex{end of list entry!in location list}
1494 end of list entry each
1495 consist of two (constant or relocated) address offsets. The two
1496 offsets are the same size as an address on the target machine.
1498 For a \addtoindex{location list} to be specified, the base address of
1499 \addtoindexx{base address selection entry!in location list}
1500 the corresponding compilation unit must be defined
1501 (see Section \refersec{chap:normalandpartialcompilationunitentries}).
1503 \section{Base Type Attribute Encodings}
1504 \label{datarep:basetypeattributeencodings}
1506 The encodings of the
1507 \hypertarget{chap:DWATencodingencodingofbasetype}
1509 \addtoindexx{encoding attribute!encoding}
1511 \livelink{chap:DWATencoding}{DW\-\_AT\-\_encoding}
1512 attribute are given in
1513 Table \refersec{tab:basetypeencodingvalues}
1516 \setlength{\extrarowheight}{0.1cm}
1517 \begin{longtable}{l|c}
1518 \caption{Base type encoding values} \label{tab:basetypeencodingvalues} \\
1519 \hline \\ \bfseries Base type encoding code name&\bfseries Value \\ \hline
1521 \bfseries Base type encoding code name&\bfseries Value\\ \hline
1523 \hline \emph{Continued on next page}
1528 \livelink{chap:DWATEaddress}{DW\-\_ATE\-\_address}&0x01 \\
1529 \livelink{chap:DWATEboolean}{DW\-\_ATE\-\_boolean}&0x02 \\
1530 \livelink{chap:DWATEcomplexfloat}{DW\-\_ATE\-\_complex\-\_float}&0x03 \\
1531 \livelink{chap:DWATEfloat}{DW\-\_ATE\-\_float}&0x04 \\
1532 \livelink{chap:DWATEsigned}{DW\-\_ATE\-\_signed}&0x05 \\
1533 \livelink{chap:DWATEsignedchar}{DW\-\_ATE\-\_signed\-\_char}&0x06 \\
1534 \livelink{chap:DWATEunsigned}{DW\-\_ATE\-\_unsigned}&0x07 \\
1535 \livelink{chap:DWATEunsignedchar}{DW\-\_ATE\-\_unsigned\-\_char}&0x08 \\
1536 \livelink{chap:DWATEimaginaryfloat}{DW\-\_ATE\-\_imaginary\-\_float}&0x09 \\
1537 \livelink{chap:DWATEpackeddecimal}{DW\-\_ATE\-\_packed\-\_decimal}&0x0a \\
1538 \livelink{chap:DWATEnumericstring}{DW\-\_ATE\-\_numeric\-\_string}&0x0b \\
1539 \livelink{chap:DWATEedited}{DW\-\_ATE\-\_edited}&0x0c \\
1540 \livelink{chap:DWATEsignedfixed}{DW\-\_ATE\-\_signed\-\_fixed}&0x0d \\
1541 \livelink{chap:DWATEunsignedfixed}{DW\-\_ATE\-\_unsigned\-\_fixed}&0x0e \\
1542 \livelink{chap:DWATEdecimalfloat}{DW\-\_ATE\-\_decimal\-\_float} & 0x0f \\
1543 \livelink{chap:DWATEUTF}{DW\-\_ATE\-\_UTF} \ddag & 0x10 \\
1544 \livetarg{chap:DWATElouser}{DW\-\_ATE\-\_lo\-\_user} & 0x80 \\
1545 \livetarg{chap:DWATEhiuser}{DW\-\_ATE\-\_hi\-\_user} & 0xff \\
1548 \ddag Base type encoding new in \addtoindex{DWARF Version 4}
1552 The encodings of the constants used in the
1553 \livelink{chap:DWATdecimalsign}{DW\-\_AT\-\_decimal\-\_sign} attribute
1555 Table \refersec{tab:decimalsignencodings}.
1559 \setlength{\extrarowheight}{0.1cm}
1560 \begin{longtable}{l|c}
1561 \caption{Decimal sign encodings} \label{tab:decimalsignencodings} \\
1562 \hline \\ \bfseries Decimal sign code name&\bfseries Value \\ \hline
1564 \bfseries Decimal sign code name&\bfseries Value\\ \hline
1566 \hline \emph{Continued on next page}
1571 \livelink{chap:DWDSunsigned}{DW\-\_DS\-\_unsigned} & 0x01 \\
1572 \livelink{chap:DWDSleadingoverpunch}{DW\-\_DS\-\_leading\-\_overpunch} & 0x02 \\
1573 \livelink{chap:DWDStrailingoverpunch}{DW\-\_DS\-\_trailing\-\_overpunch} & 0x03 \\
1574 \livelink{chap:DWDSleadingseparate}{DW\-\_DS\-\_leading\-\_separate} & 0x04 \\
1575 \livelink{chap:DWDStrailingseparate}{DW\-\_DS\-\_trailing\-\_separate} & 0x05 \\
1580 The encodings of the constants used in the
1581 \livelink{chap:DWATendianity}{DW\-\_AT\-\_endianity} attribute are given in
1582 Table \refersec{tab:endianityencodings}.
1585 \setlength{\extrarowheight}{0.1cm}
1586 \begin{longtable}{l|c}
1587 \caption{Endianity encodings} \label{tab:endianityencodings}\\
1588 \hline \\ \bfseries Endian code name&\bfseries Value \\ \hline
1590 \bfseries Endian code name&\bfseries Value\\ \hline
1592 \hline \emph{Continued on next page}
1597 \livelink{chap:DWENDdefault}{DW\-\_END\-\_default} & 0x00 \\
1598 \livelink{chap:DWENDbig}{DW\-\_END\-\_big} & 0x01 \\
1599 \livelink{chap:DWENDlittle}{DW\-\_END\-\_little} & 0x02 \\
1600 \livetarg{chap:DWENDlouser}{DW\-\_END\-\_lo\-\_user} & 0x40 \\
1601 \livetarg{chap:DWENDhiuser}{DW\-\_END\-\_hi\-\_user} & 0xff \\
1606 \section{Accessibility Codes}
1607 \label{datarep:accessibilitycodes}
1608 The encodings of the constants used in the
1609 \livelink{chap:DWATaccessibility}{DW\-\_AT\-\_accessibility}
1611 \addtoindexx{accessibility attribute!encoding}
1613 Table \refersec{tab:accessibilityencodings}.
1616 \setlength{\extrarowheight}{0.1cm}
1617 \begin{longtable}{l|c}
1618 \caption{Accessibility encodings} \label{tab:accessibilityencodings}\\
1619 \hline \\ \bfseries Accessibility code name&\bfseries Value \\ \hline
1621 \bfseries Accessibility code name&\bfseries Value\\ \hline
1623 \hline \emph{Continued on next page}
1628 \livelink{chap:DWACCESSpublic}{DW\-\_ACCESS\-\_public}&0x01 \\
1629 \livelink{chap:DWACCESSprotected}{DW\-\_ACCESS\-\_protected}&0x02 \\
1630 \livelink{chap:DWACCESSprivate}{DW\-\_ACCESS\-\_private}&0x03 \\
1636 \section{Visibility Codes}
1637 \label{datarep:visibilitycodes}
1638 The encodings of the constants used in the
1639 \livelink{chap:DWATvisibility}{DW\-\_AT\-\_visibility} attribute are given in
1640 Table \refersec{tab:visibilityencodings}.
1643 \setlength{\extrarowheight}{0.1cm}
1644 \begin{longtable}{l|c}
1645 \caption{Visibility encodings} \label{tab:visibilityencodings}\\
1646 \hline \\ \bfseries Visiibility code name&\bfseries Value \\ \hline
1648 \bfseries Visibility code name&\bfseries Value\\ \hline
1650 \hline \emph{Continued on next page}
1655 \livelink{chap:DWVISlocal}{DW\-\_VIS\-\_local}&0x01 \\
1656 \livelink{chap:DWVISexported}{DW\-\_VIS\-\_exported}&0x02 \\
1657 \livelink{chap:DWVISqualified}{DW\-\_VIS\-\_qualified}&0x03 \\
1662 \section{Virtuality Codes}
1663 \label{datarep:vitualitycodes}
1665 The encodings of the constants used in the
1666 \livelink{chap:DWATvirtuality}{DW\-\_AT\-\_virtuality} attribute are given in
1667 Table \refersec{tab:virtualityencodings}.
1670 \setlength{\extrarowheight}{0.1cm}
1671 \begin{longtable}{l|c}
1672 \caption{Virtuality encodings} \label{tab:virtualityencodings}\\
1673 \hline \\ \bfseries Virtuality code name&\bfseries Value \\ \hline
1675 \bfseries Virtuality code name&\bfseries Value\\ \hline
1677 \hline \emph{Continued on next page}
1682 \livelink{chap:DWVIRTUALITYnone}{DW\-\_VIRTUALITY\-\_none}&0x00 \\
1683 \livelink{chap:DWVIRTUALITYvirtual}{DW\-\_VIRTUALITY\-\_virtual}&0x01 \\
1684 \livelink{chap:DWVIRTUALITYpurevirtual}{DW\-\_VIRTUALITY\-\_pure\-\_virtual}&0x02 \\
1692 \livelink{chap:DWVIRTUALITYnone}{DW\-\_VIRTUALITY\-\_none} is equivalent to the absence of the
1693 \livelink{chap:DWATvirtuality}{DW\-\_AT\-\_virtuality}
1696 \section{Source Languages}
1697 \label{datarep:sourcelanguages}
1699 The encodings of the constants used
1700 \addtoindexx{language attribute, encoding}
1702 \addtoindexx{language name encoding}
1704 \livelink{chap:DWATlanguage}{DW\-\_AT\-\_language}
1705 attribute are given in
1706 Table \refersec{tab:languageencodings}.
1708 % If we don't force a following space it looks odd
1710 and their associated values are reserved, but the
1711 languages they represent are not well supported.
1712 Table \refersec{tab:languageencodings}
1714 \addtoindexx{lower bound attribute!default}
1715 default lower bound, if any, assumed for
1716 an omitted \livelink{chap:DWATlowerbound}{DW\-\_AT\-\_lower\-\_bound} attribute in the context of a
1717 \livelink{chap:DWTAGsubrangetype}{DW\-\_TAG\-\_subrange\-\_type} debugging information entry for each
1721 \setlength{\extrarowheight}{0.1cm}
1722 \begin{longtable}{l|c|c}
1723 \caption{Language encodings} \label{tab:languageencodings}\\
1724 \hline \\ \bfseries Language name&\bfseries Value &\bfseries Default Lower Bound \\ \hline
1726 \bfseries Language name&\bfseries Value &\bfseries Default Lower Bound\\ \hline
1728 \hline \emph{Continued on next page}
1733 \livelink{chap:DWLANGC89}{DW\-\_LANG\-\_C89}&0x0001&0 \\
1734 \livelink{chap:DWLANGC}{DW\-\_LANG\-\_C}&0x0002&0 \\
1735 \livelink{chap:DWLANGAda83}{DW\-\_LANG\-\_Ada83} \dag &0x0003&1 \addtoindexx{Ada} \\
1736 \livelink{chap:DWLANGCplusplus}{DW\-\_LANG\-\_C\-\_plus\-\_plus} &0x0004&0 \\
1737 \livelink{chap:DWLANGCobol74}{DW\-\_LANG\-\_Cobol74} \dag &0x0005&1 \\
1738 \livelink{chap:DWLANGCobol85}{DW\-\_LANG\-\_Cobol85} \dag &0x0006&1 \\
1739 \livelink{chap:DWLANGFortran77}{DW\-\_LANG\-\_Fortran77}&0x0007&1 \\
1740 \livelink{chap:DWLANGFortran90}{DW\-\_LANG\-\_Fortran90}&0x0008&1 \\
1741 \livelink{chap:DWLANGPascal83}{DW\-\_LANG\-\_Pascal83}&0x0009&1 \\
1742 \livelink{chap:DWLANGModula2}{DW\-\_LANG\-\_Modula2}&0x000a&1 \\
1743 \livelink{chap:DWLANGJava}{DW\-\_LANG\-\_Java}&0x000b&0 \\
1744 \livelink{chap:DWLANGC99}{DW\-\_LANG\-\_C99}&0x000c&0 \\
1745 \livelink{chap:DWLANGAda95}{DW\-\_LANG\-\_Ada95} \dag &0x000d&1 \addtoindexx{Ada} \\
1746 \livelink{chap:DWLANGFortran95}{DW\-\_LANG\-\_Fortran95} &0x000e&1 \\
1747 \livelink{chap:DWLANGPLI}{DW\-\_LANG\-\_PLI} \dag &0x000f&1 \\
1748 \livelink{chap:DWLANGObjC}{DW\-\_LANG\-\_ObjC}&0x0010&0 \\
1749 \livelink{chap:DWLANGObjCplusplus}{DW\-\_LANG\-\_ObjC\-\_plus\-\_plus}&0x0011&0 \\
1750 \livelink{chap:DWLANGUPC}{DW\-\_LANG\-\_UPC}&0x0012&0 \\
1751 \livelink{chap:DWLANGD}{DW\-\_LANG\-\_D}&0x0013&0 \\
1752 \livelink{chap:DWLANGPython}{DW\-\_LANG\-\_Python} \dag &0x0014&0 \\
1753 \livetarg{chap:DWLANGlouser}{DW\-\_LANG\-\_lo\-\_user}&0x8000 & \\
1754 \livetarg{chap:DWLANGhiuser}{DW\-\_LANG\-\_hi\-\_user}&0xffff & \\
1760 \section{Address Class Encodings}
1761 \label{datarep:addressclassencodings}
1763 The value of the common
1764 \addtoindexi{address}{address class!attribute encoding}
1766 \livelink{chap:DWADDRnone}{DW\-\_ADDR\-\_none} is 0.
1769 \section{Identifier Case}
1770 \label{datarep:identifiercase}
1772 The encodings of the constants used in the
1773 \livelink{chap:DWATidentifiercase}{DW\-\_AT\-\_identifier\-\_case} attribute are given in
1774 Table \refersec{tab:identifiercaseencodings}.
1777 \setlength{\extrarowheight}{0.1cm}
1778 \begin{longtable}{l|c}
1779 \caption{Identifier case encodings} \label{tab:identifiercaseencodings}\\
1780 \hline \\ \bfseries Identifier case name&\bfseries Value \\ \hline
1782 \bfseries Identifier case name&\bfseries Value\\ \hline
1784 \hline \emph{Continued on next page}
1788 \livelink{chap:DWIDcasesensitive}{DW\-\_ID\-\_case\-\_sensitive}&0x00 \\
1789 \livelink{chap:DWIDupcase}{DW\-\_ID\-\_up\-\_case}&0x01 \\
1790 \livelink{chap:DWIDdowncase}{DW\-\_ID\-\_down\-\_case}&0x02 \\
1791 \livelink{chap:DWIDcaseinsensitive}{DW\-\_ID\-\_case\-\_insensitive}&0x03 \\
1795 \section{Calling Convention Encodings}
1796 \label{datarep:callingconventionencodings}
1797 The encodings of the constants used in the
1798 \livelink{chap:DWATcallingconvention}{DW\-\_AT\-\_calling\-\_convention} attribute are given in
1799 Table \refersec{tab:callingconventionencodings}.
1802 \setlength{\extrarowheight}{0.1cm}
1803 \begin{longtable}{l|c}
1804 \caption{Calling convention encodings} \label{tab:callingconventionencodings}\\
1805 \hline \\ \bfseries Calling Convention name&\bfseries Value \\ \hline
1807 \bfseries Calling Convention name&\bfseries Value\\ \hline
1809 \hline \emph{Continued on next page}
1814 \livelink{chap:DWCCnormal}{DW\-\_CC\-\_normal}&0x01 \\
1815 \livelink{chap:DWCCprogram}{DW\-\_CC\-\_program}&0x02 \\
1816 \livelink{chap:DWCCnocall}{DW\-\_CC\-\_nocall}&0x03 \\
1817 \livetarg{chap:DWCClouser}{DW\-\_CC\-\_lo\-\_user}&0x40 \\
1818 \livetarg{chap:DWCChiuser}{DW\-\_CC\-\_hi\-\_user}&0xff \\
1823 \section{Inline Codes}
1824 \label{datarep:inlinecodes}
1826 The encodings of the constants used in
1827 \addtoindexx{inline attribute!encoding}
1829 \livelink{chap:DWATinline}{DW\-\_AT\-\_inline} attribute are given in
1830 Table \refersec{tab:inlineencodings}.
1833 \setlength{\extrarowheight}{0.1cm}
1834 \begin{longtable}{l|c}
1835 \caption{Inline encodings} \label{tab:inlineencodings}\\
1836 \hline \\ \bfseries Iline Code name&\bfseries Value \\ \hline
1838 \bfseries Iline Code name&\bfseries Value\\ \hline
1840 \hline \emph{Continued on next page}
1845 \livelink{chap:DWINLnotinlined}{DW\-\_INL\-\_not\-\_inlined}&0x00 \\
1846 \livelink{chap:DWINLinlined}{DW\-\_INL\-\_inlined}&0x01 \\
1847 \livelink{chap:DWINLdeclarednotinlined}{DW\-\_INL\-\_declared\-\_not\-\_inlined}&0x02 \\
1848 \livelink{chap:DWINLdeclaredinlined}{DW\-\_INL\-\_declared\-\_inlined}&0x03 \\
1853 % this clearpage is ugly, but the following table came
1854 % out oddly without it.
1856 \section{Array Ordering}
1857 \label{datarep:arrayordering}
1859 The encodings of the constants used in the
1860 \livelink{chap:DWATordering}{DW\-\_AT\-\_ordering} attribute are given in
1861 Table \refersec{tab:orderingencodings}.
1864 \setlength{\extrarowheight}{0.1cm}
1865 \begin{longtable}{l|c}
1866 \caption{Ordering encodings} \label{tab:orderingencodings}\\
1867 \hline \\ \bfseries Ordering name&\bfseries Value \\ \hline
1869 \bfseries Ordering name&\bfseries Value\\ \hline
1871 \hline \emph{Continued on next page}
1876 \livelink{chap:DWORDrowmajor}{DW\-\_ORD\-\_row\-\_major}&0x00 \\
1877 \livelink{chap:DWORDcolmajor}{DW\-\_ORD\-\_col\-\_major}&0x01 \\
1883 \section{Discriminant Lists}
1884 \label{datarep:discriminantlists}
1886 The descriptors used in
1887 \addtoindexx{discriminant list attribute!encoding}
1889 \livelink{chap:DWATdiscrlist}{DW\-\_AT\-\_discr\-\_list} attribute are
1890 encoded as 1\dash byte constants. The
1891 defined values are given in
1892 Table \refersec{tab:discriminantdescriptorencodings}.
1894 % Odd that the 'Name' field captalized here, it is not caps elsewhere.
1896 \setlength{\extrarowheight}{0.1cm}
1897 \begin{longtable}{l|c}
1898 \caption{Discriminant descriptor encodings} \label{tab:discriminantdescriptorencodings}\\
1899 \hline \\ \bfseries Descriptor Name&\bfseries Value \\ \hline
1901 \bfseries Descriptor Name&\bfseries Value\\ \hline
1903 \hline \emph{Continued on next page}
1908 \livetarg{chap:DWDSClabel}{DW\-\_DSC\-\_label}&0x00 \\
1909 \livetarg{chap:DWDSCrange}{DW\-\_DSC\-\_range}&0x01 \\
1914 \section{Name Lookup Tables}
1915 \label{datarep:namelookuptables}
1917 Each set of entries in the table of global names contained
1918 in the \addtoindex{.debug\_pubnames} and
1919 \addtoindex{.debug\_pubtypes} sections begins
1920 with a header consisting of:
1923 \begin{enumerate}[1.]
1924 \item unit\_length (initial length) \\
1925 A 4\dash byte or 12\dash byte unsigned integer
1926 \addtoindexx{initial length}
1927 representing the length
1928 of the \addtoindex{.debug\_info}
1929 contribution for that compilation unit,
1930 not including the length field itself. In the 32\dash bit DWARF
1931 format, this is a 4\dash byte unsigned integer (which must be less
1932 than 0xfffffff0); in the 64\dash bit DWARF format, this consists
1933 of the 4\dash byte value 0xffffffff followed by an 8\dash byte unsigned
1934 integer that gives the actual length
1935 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
1937 \item version (uhalf)
1938 A 2\dash byte unsigned integer representing the version of the
1939 DWARF information\addtoindexx{version number!compilation unit} for the compilation unit
1940 \addtoindexx{version number!name lookup table}
1941 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
1942 The value in this field is 4.
1944 % Some say unsigned offset this just says offset: FIXME
1945 \item \addtoindex{debug\_info\_offset} (section offset) \\
1947 \addtoindexx{section offset!in name lookup table set of entries}
1948 4\dash byte or 8\dash byte
1950 \addtoindex{.debug\_info}
1951 section of the compilation unit header.
1953 the 32\dash bit DWARF format, this is a 4\dash byte unsigned offset;
1954 in the 64\dash bit DWARF format, this is an 8\dash byte unsigned offsets
1955 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
1957 \item \addtoindex{debug\_info\_length} (section length) \\
1958 \addtoindexx{section length!in .debug\_pubnames header}
1960 \addtoindexx{section length!in .debug\_pubtypes header}
1961 4\dash byte or 8\dash byte length containing the size in bytes of the
1962 contents of the \addtoindex{.debug\_info}
1963 section generated to represent
1964 this compilation unit. In the 32\dash bit DWARF format, this is
1965 a 4\dash byte unsigned length; in the 64\dash bit DWARF format, this
1966 is an 8-byte unsigned length
1967 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
1972 This header is followed by a series of tuples. Each tuple
1973 consists of a 4\dash byte or 8\dash byte offset followed by a string
1974 of non\dash null bytes terminated by one null byte.
1976 DWARF format, this is a 4\dash byte offset; in the 64\dash bit DWARF
1977 format, it is an 8\dash byte offset.
1978 Each set is terminated by an
1979 offset containing the value 0.
1982 \section{Address Range Table}
1983 \label{datarep:addrssrangetable}
1985 Each set of entries in the table of address ranges contained
1986 in the \addtoindex{.debug\_aranges}
1987 section begins with a header containing:
1989 \begin{enumerate}[1.]
1990 % FIXME The unit length text is not fully consistent across
1993 \item unit\_length (initial length) \\
1994 A 4-byte or 12-byte length containing the length of the
1995 \addtoindexx{initial length}
1996 set of entries for this compilation unit, not including the
1997 length field itself. In the 32-bit DWARF format, this is a
1998 4-byte unsigned integer (which must be less than 0xfffffff0);
1999 in the 64-bit DWARF format, this consists of the 4-byte value
2000 0xffffffff followed by an 8-byte unsigned integer that gives
2002 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
2004 \item version (uhalf) \\
2005 A 2\dash byte version identifier
2006 \addtoindexx{version number!address range table} containing the value 2
2007 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
2009 \item debug\_info\_offset (section offset) \\
2011 \addtoindexx{section offset!in .debug\_aranges header}
2012 4\dash byte or 8\dash byte offset into the
2013 \addtoindex{.debug\_info} section of
2014 the compilation unit header. In the 32\dash bit DWARF format,
2015 this is a 4\dash byte unsigned offset; in the 64\dash bit DWARF format,
2016 this is an 8\dash byte unsigned offset
2017 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
2019 \item address\_size (ubyte) \\
2020 A 1\dash byte unsigned integer containing the size in bytes of an
2021 \addtoindexx{address\_size}
2023 \addtoindexx{size of an address}
2024 (or the offset portion of an address for segmented
2025 \addtoindexx{address space!segmented}
2026 addressing) on the target system.
2028 \item segment\_size (ubyte) \\
2030 \addtoindexx{segment\_size}
2031 1\dash byte unsigned integer containing the size in bytes of a
2032 segment selector on the target system.
2036 This header is followed by a series of tuples. Each tuple
2037 consists of a segment, an address and a length.
2039 size is given by the \addtoindex{segment\_size} field of the header; the
2040 address and length size are each given by the address\_size
2041 field of the header.
2042 The first tuple following the header in
2043 each set begins at an offset that is a multiple of the size
2044 of a single tuple (that is, the size of a segment selector
2045 plus twice the \addtoindex{size of an address}).
2046 The header is padded, if
2047 necessary, to that boundary. Each set of tuples is terminated
2048 by a 0 for the segment, a 0 for the address and 0 for the
2049 length. If the \addtoindex{segment\_size} field in the header is zero,
2050 the segment selectors are omitted from all tuples, including
2051 the terminating tuple.
2054 \section{Line Number Information}
2055 \label{datarep:linenumberinformation}
2057 The \addtoindexi{version number}{version number!line number information}
2058 in the line number program header is 4
2059 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
2061 The boolean values ``true'' and ``false''
2062 used by the line number information program are encoded
2063 as a single byte containing the value 0
2064 for ``false,'' and a non-zero value for ``true.''
2066 The encodings for the standard opcodes are given in
2067 \addtoindexx{line number opcodes!standard opcode encoding}
2068 Table \refersec{tab:linenumberstandardopcodeencodings}.
2070 % Odd that the 'Name' field captalized here, it is not caps elsewhere.
2072 \setlength{\extrarowheight}{0.1cm}
2073 \begin{longtable}{l|c}
2074 \caption{Line Number Standard Opcode encodings} \label{tab:linenumberstandardopcodeencodings}\\
2075 \hline \\ \bfseries Opcode Name&\bfseries Value \\ \hline
2077 \bfseries Opcode Name&\bfseries Value\\ \hline
2079 \hline \emph{Continued on next page}
2084 \livelink{chap:DWLNScopy}{DW\-\_LNS\-\_copy}&0x01 \\
2085 \livelink{chap:DWLNSadvancepc}{DW\-\_LNS\-\_advance\-\_pc}&0x02 \\
2086 \livelink{chap:DWLNSadvanceline}{DW\-\_LNS\-\_advance\-\_line}&0x03 \\
2087 \livelink{chap:DWLNSsetfile}{DW\-\_LNS\-\_set\-\_file}&0x04 \\
2088 \livelink{chap:DWLNSsetcolumn}{DW\-\_LNS\-\_set\-\_column}&0x05 \\
2089 \livelink{chap:DWLNSnegatestmt}{DW\-\_LNS\-\_negate\-\_stmt}&0x06 \\
2090 \livelink{chap:DWLNSsetbasicblock}{DW\-\_LNS\-\_set\-\_basic\-\_block}&0x07 \\
2091 \livelink{chap:DWLNSconstaddpc}{DW\-\_LNS\-\_const\-\_add\-\_pc}*0x08 \\
2092 \livelink{chap:DWLNSfixedadvancepc}{DW\-\_LNS\-\_fixed\-\_advance\-\_pc}&0x09 \\
2093 \livelink{chap:DWLNSsetprologueend}{DW\-\_LNS\-\_set\-\_prologue\-\_end}&0x0a \\
2094 \livelink{chap:DWLNSsetepiloguebegin}{DW\-\_LNS\-\_set\-\_epilogue\-\_begin}&0x0b \\
2095 \livelink{chap:DWLNSsetisa}{DW\-\_LNS\-\_set\-\_isa}&0x0c \\
2101 The encodings for the extended opcodes are given in
2102 \addtoindexx{line number opcodes!extended opcode encoding}
2103 Table \refersec{tab:linenumberextendedopcodeencodings}.
2106 \setlength{\extrarowheight}{0.1cm}
2107 \begin{longtable}{l|c}
2108 \caption{Line Number Extended Opcode encodings} \label{tab:linenumberextendedopcodeencodings}\\
2109 \hline \\ \bfseries Opcode Name&\bfseries Value \\ \hline
2111 \bfseries Opcode Name&\bfseries Value\\ \hline
2113 \hline \emph{Continued on next page}
2118 \livelink{chap:DWLNEendsequence}{DW\-\_LNE\-\_end\-\_sequence}&0x01 \\
2119 \livelink{chap:DWLNEsetaddress}{DW\-\_LNE\-\_set\-\_address}&0x02\\
2120 \livelink{chap:DWLNEdefinefile}{DW\-\_LNE\-\_define\-\_file}&0x03\\
2121 \livelink{chap:DWLNEsetdiscriminator}{DW\-\_LNE\-\_set\-\_discriminator} \ddag &0x04 \\
2122 \livetarg{chap:DWLNElouser}{DW\-\_LNE\-\_lo\-\_user}&0x80 \\
2123 \livetarg{chap:DWLNEhiuser}{DW\-\_LNE\-\_hi\-\_user}&0xff \\
2126 \ddag Extended opcode new in \addtoindex{DWARF Version 4}.
2129 \section{Macro Information}
2130 \label{datarep:macroinformation}
2132 The source line numbers and source file indices encoded in the
2133 macro information section are represented as unsigned LEB128
2134 numbers as are the constants in a
2135 \livelink{chap:DWMACINFOvendorext}{DW\-\_MACINFO\-\_vendor\-\_ext} entry.
2137 The macinfo type is encoded as a single byte.
2139 \addtoindexx{macinfo types!encoding}
2141 Table \refersec{tab:macinfotypeencodings}.
2145 \setlength{\extrarowheight}{0.1cm}
2146 \begin{longtable}{l|c}
2147 \caption{Macinfo Type Encodings} \label{tab:macinfotypeencodings}\\
2148 \hline \\ \bfseries Macinfo Type Name&\bfseries Value \\ \hline
2150 \bfseries Macinfo Type Name&\bfseries Value\\ \hline
2152 \hline \emph{Continued on next page}
2157 \livelink{chap:DWMACINFOdefine}{DW\-\_MACINFO\-\_define}&0x01 \\
2158 \livelink{chap:DWMACINFOundef}{DW\-\_MACINFO\-\_undef}&0x02 \\
2159 \livelink{chap:DWMACINFOstartfile}{DW\-\_MACINFO\-\_start\-\_file}&0x03 \\
2160 \livelink{chap:DWMACINFOendfile}{DW\-\_MACINFO\-\_end\-\_file}&0x04 \\
2161 \livelink{chap:DWMACINFOvendorext}{DW\-\_MACINFO\-\_vendor\-\_ext}&0xff \\
2166 \section{Call Frame Information}
2167 \label{datarep:callframeinformation}
2169 In the 32\dash bit DWARF format, the value of the CIE id in the
2170 CIE header is 0xffffffff; in the 64\dash bit DWARF format, the
2171 value is 0xffffffffffffffff.
2173 The value of the CIE \addtoindexi{version number}{version number!call frame information}
2174 is 4 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
2176 Call frame instructions are encoded in one or more bytes. The
2177 primary opcode is encoded in the high order two bits of
2178 the first byte (that is, opcode = byte >> 6). An operand
2179 or extended opcode may be encoded in the low order 6
2180 bits. Additional operands are encoded in subsequent bytes.
2181 The instructions and their encodings are presented in
2182 Table \refersec{tab:callframeinstructionencodings}.
2185 \setlength{\extrarowheight}{0.1cm}
2186 \begin{longtable}{l|c|c|l|l}
2187 \caption{Call frame instruction encodings} \label{tab:callframeinstructionencodings} \\
2188 \hline \\ &\bfseries High 2 &\bfseries Low 6 & & \\
2189 \bfseries Instruction&\bfseries Bits &\bfseries Bits &\bfseries Operand 1 &\bfseries Operand 2\\ \hline
2191 & \bfseries High 2 &\bfseries Low 6 & &\\
2192 \bfseries Instruction&\bfseries Bits &\bfseries Bits &\bfseries Operand 1 &\bfseries Operand 2\\ \hline
2194 \hline \emph{Continued on next page}
2199 \livelink{chap:DWCFAadvanceloc}{DW\-\_CFA\-\_advance\-\_loc}&0x1&delta & \\
2200 \livelink{chap:DWCFAoffset}{DW\-\_CFA\-\_offset}&0x2®ister&ULEB128 offset \\
2201 \livelink{chap:DWCFArestore}{DW\-\_CFA\-\_restore}&0x3®ister & & \\
2202 \livelink{chap:DWCFAnop}{DW\-\_CFA\-\_nop}&0&0 & & \\
2203 \livelink{chap:DWCFAsetloc}{DW\-\_CFA\-\_set\-\_loc}&0&0x01&address & \\
2204 \livelink{chap:DWCFAadvanceloc1}{DW\-\_CFA\-\_advance\-\_loc1}&0&0x02&1\dash byte delta & \\
2205 \livelink{chap:DWCFAadvanceloc2}{DW\-\_CFA\-\_advance\-\_loc2}&0&0x03&2\dash byte delta & \\
2206 \livelink{chap:DWCFAadvanceloc4}{DW\-\_CFA\-\_advance\-\_loc4}&0&0x04&4\dash byte delta & \\
2207 \livelink{chap:DWCFAoffsetextended}{DW\-\_CFA\-\_offset\-\_extended}&0&0x05&ULEB128 register&ULEB128 offset \\
2208 \livelink{chap:DWCFArestoreextended}{DW\-\_CFA\-\_restore\-\_extended}&0&0x06&ULEB128 register & \\
2209 \livelink{chap:DWCFAundefined}{DW\-\_CFA\-\_undefined}&0&0x07&ULEB128 register & \\
2210 \livelink{chap:DWCFAsamevalue}{DW\-\_CFA\-\_same\-\_value}&0&0x08 &ULEB128 register & \\
2211 \livelink{chap:DWCFAregister}{DW\-\_CFA\-\_register}&0&0x09&ULEB128 register &ULEB128 offset \\
2212 \livelink{chap:DWCFArememberstate}{DW\-\_CFA\-\_remember\-\_state}&0&0x0a & & \\
2213 \livelink{chap:DWCFArestorestate}{DW\-\_CFA\-\_restore\-\_state}&0&0x0b & & \\
2214 \livelink{chap:DWCFAdefcfa}{DW\-\_CFA\-\_def\-\_cfa}&0&0x0c &ULEB128 register&ULEB128 offset \\
2215 \livelink{chap:DWCFAdefcfaregister}{DW\-\_CFA\-\_def\-\_cfa\-\_register}&0&0x0d&ULEB128 register & \\
2216 \livelink{chap:DWCFAdefcfaoffset}{DW\-\_CFA\-\_def\-\_cfa\-\_offset}&0&0x0e &ULEB128 offset & \\
2217 \livelink{chap:DWCFAdefcfaexpression}{DW\-\_CFA\-\_def\-\_cfa\-\_expression}&0&0x0f &BLOCK \\
2218 \livelink{chap:DWCFAexpression}{DW\-\_CFA\-\_expression}&0&0x10&ULEB128 register & BLOCK \\
2220 \livelink{chap:DWCFAoffsetextendedsf}{DW\-\_CFA\-\_offset\-\_extended\-\_sf}&0&0x11&ULEB128 register&SLEB128 offset \\
2221 \livelink{chap:DWCFAdefcfasf}{DW\-\_CFA\-\_def\-\_cfa\-\_sf}&0&0x12&ULEB128 register&SLEB128 offset \\
2222 \livelink{chap:DWCFAdefcfaoffsetsf}{DW\-\_CFA\-\_def\-\_cfa\-\_offset\-\_sf}&0&0x13&SLEB128 offset & \\
2223 \livelink{chap:DWCFAvaloffset}{DW\-\_CFA\-\_val\-\_offset}&0&0x14&ULEB128&ULEB128 \\
2224 \livelink{chap:DWCFAvaloffsetsf}{DW\-\_CFA\-\_val\-\_offset\-\_sf}&0&0x15&ULEB128&SLEB128 \\
2225 \livelink{chap:DWCFAvalexpression}{DW\-\_CFA\-\_val\-\_expression}&0&0x16&ULEB128&BLOCK \\
2226 \livetarg{chap:DWCFAlouser}{DW\-\_CFA\-\_lo\-\_user}&0&0x1c & & \\
2227 \livetarg{chap:DWCFAhiuser}{DW\-\_CFA\-\_hi\-\_user}&0&0x3f & & \\
2231 \section{Non-continguous Address Ranges}
2232 \label{datarep:noncontiguousaddressranges}
2234 Each entry in a \addtoindex{range list}
2235 (see Section \refersec{chap:noncontiguousaddressranges})
2237 \addtoindexx{base address selection entry!in range list}
2239 \addtoindexx{range list}
2240 a base address selection entry, or an end
2243 A \addtoindex{range list} entry consists of two relative addresses. The
2244 addresses are the same size as addresses on the target machine.
2246 A base address selection entry and an
2247 \addtoindex{end of list entry!in range list}
2248 end of list entry each
2249 \addtoindexx{base address selection entry!in range list}
2250 consist of two (constant or relocated) addresses. The two
2251 addresses are the same size as addresses on the target machine.
2253 For a \addtoindex{range list} to be specified, the base address of the
2254 \addtoindexx{base address selection entry!in range list}
2255 corresponding compilation unit must be defined
2256 (see Section \refersec{chap:normalandpartialcompilationunitentries}).
2259 \section{Dependencies and Constraints}
2260 \label{datarep:dependenciesandconstraints}
2262 The debugging information in this format is intended to
2264 \addtoindexx{DWARF section names!list of}
2266 the \addtoindex{.debug\_abbrev},
2267 \addtoindex{.debug\_aranges},
2268 \addtoindex{.debug\_frame},
2269 \addtoindex{.debug\_info},
2270 \addtoindex{.debug\_line},
2271 \addtoindex{.debug\_loc},
2272 \addtoindex{.debug\_macinfo},
2273 \addtoindex{.debug\_pubnames},
2274 \addtoindex{.debug\_pubtypes},
2275 \addtoindex{.debug\_ranges},
2276 \addtoindex{.debug\_str}
2278 \addtoindex{.debug\_types}
2279 sections of an object file, or equivalent
2280 separate file or database. The information is not
2281 word\dash aligned. Consequently: •
2284 \item For the 32\dash bit DWARF format and a target architecture with
2285 32\dash bit addresses, an assembler or compiler must provide a way
2286 to produce 2\dash byte and 4\dash byte quantities without alignment
2287 restrictions, and the linker must be able to relocate a
2288 4\dash byte address or
2289 \addtoindexx{section offset!alignment of}
2290 section offset that occurs at an arbitrary
2293 \item For the 32\dash bit DWARF format and a target architecture with
2294 64\dash bit addresses, an assembler or compiler must provide a
2295 way to produce 2\dash byte, 4\dash byte and 8\dash byte quantities without
2296 alignment restrictions, and the linker must be able to relocate
2297 an 8\dash byte address or 4\dash byte
2298 \addtoindexx{section offset!alignment of}
2299 section offset that occurs at an
2300 arbitrary alignment.
2302 \item For the 64\dash bit DWARF format and a target architecture with
2303 32\dash bit addresses, an assembler or compiler must provide a
2304 way to produce 2\dash byte, 4\dash byte and 8\dash byte quantities without
2305 alignment restrictions, and the linker must be able to relocate
2306 a 4\dash byte address or 8\dash byte
2307 \addtoindexx{section offset!alignment of}
2308 section offset that occurs at an
2309 arbitrary alignment.
2311 \textit{It is expected that this will be required only for very large
2312 32\dash bit programs or by those architectures which support
2313 a mix of 32\dash bit and 64\dash bit code and data within the same
2316 \item For the 64\dash bit DWARF format and a target architecture with
2317 64\dash bit addresses, an assembler or compiler must provide a
2318 way to produce 2\dash byte, 4\dash byte and 8\dash byte quantities without
2319 alignment restrictions, and the linker must be able to
2320 relocate an 8\dash byte address or
2321 \addtoindexx{section offset!alignment of}
2322 section offset that occurs at
2323 an arbitrary alignment.
2326 \section{Integer Representation Names}
2327 \label{datarep:integerrepresentationnames}
2329 The sizes of the integers used in the lookup by name, lookup
2330 by address, line number and call frame information sections
2332 Table 41 \refersec{tab:integerrepresentationnames}.
2335 \setlength{\extrarowheight}{0.1cm}
2336 \begin{longtable}{c|l}
2337 \caption{Integer Representation Names} \label{tab:integerrepresentationnames}\\
2338 \hline \\ \bfseries Representation Name&\bfseries Representation \\ \hline
2340 \bfseries Representation Name&\bfseries Representation\\ \hline
2342 \hline \emph{Continued on next page}
2347 \addtoindex{sbyte}& signed, 1\dash byte integer \\
2348 \addtoindex{ubyte}&unsigned, 1\dash byte integer \\
2349 \addtoindex{uhalf}&unsigned, 2\dash byte integer \\
2350 \addtoindex{uword}&unsigned, 4\dash byte integer \\
2355 \section{Type Signature Computation}
2356 \label{datarep:typesignaturecomputation}
2358 A type signature is computed only by the DWARF producer;
2359 \addtoindexx{type signature computation}
2360 it is used by a DWARF consumer to resolve type references to
2361 the type definitions that are contained in
2362 \addtoindexx{type unit}
2365 The type signature for a type T0 is formed from the
2366 \addtoindex{MD5 hash}
2367 of a flattened description of the type. The flattened
2368 description of the type is a byte sequence derived from the
2369 DWARF encoding of the type as follows:
2371 \begin{enumerate}[1.]
2373 \item Start with an empty sequence S and a list V of visited
2374 types, where V is initialized to a list containing the type
2375 T0 as its single element. Elements in V are indexed from 1,
2378 \item If the debugging information entry represents a type that
2379 is nested inside another type or a namespace, append to S
2380 the type’s context as follows: For each surrounding type
2381 or namespace, beginning with the outermost such construct,
2382 append the letter 'C', the DWARF tag of the construct, and
2383 the name (taken from
2384 \addtoindexx{name attribute}
2385 the \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute) of the type
2386 \addtoindexx{name attribute}
2387 or namespace (including its trailing null byte).
2389 \item Append to S the letter 'D', followed by the DWARF tag of
2390 the debugging information entry.
2392 \item For each of the following attributes that are present in
2393 the debugging information entry, in the order listed below,
2394 append to S a marker letter (see below), the DWARF attribute
2395 code, and the attribute value.
2398 \item \livelink{chap:DWATname}{DW\-\_AT\-\_name}
2399 \item \livelink{chap:DWATaccessibility}{DW\-\_AT\-\_accessibility}
2400 \item \livelink{chap:DWATaddressclass}{DW\-\_AT\-\_address\-\_class}
2401 \item \livelink{chap:DWATallocated}{DW\-\_AT\-\_allocated}
2402 \item \livelink{chap:DWATartificial}{DW\-\_AT\-\_artificial}
2403 \item \livelink{chap:DWATassociated}{DW\-\_AT\-\_associated}
2404 \item \livelink{chap:DWATbinaryscale}{DW\-\_AT\-\_binary\-\_scale}
2405 \item \livelink{chap:DWATbitoffset}{DW\-\_AT\-\_bit\-\_offset}
2406 \item \livelink{chap:DWATbitsize}{DW\-\_AT\-\_bit\-\_size}
2407 \item \livelink{chap:DWATbitstride}{DW\-\_AT\-\_bit\-\_stride}
2408 \item \livelink{chap:DWATbytesize}{DW\-\_AT\-\_byte\-\_size}
2409 \item \livelink{chap:DWATbytestride}{DW\-\_AT\-\_byte\-\_stride}
2410 \item \livelink{chap:DWATconstexpr}{DW\-\_AT\-\_const\-\_expr}
2411 \item \livelink{chap:DWATconstvalue}{DW\-\_AT\-\_const\-\_value}
2412 \item \livelink{chap:DWATcontainingtype}{DW\-\_AT\-\_containing\-\_type}
2413 \item \livelink{chap:DWATcount}{DW\-\_AT\-\_count}
2414 \item \livelink{chap:DWATdatabitoffset}{DW\-\_AT\-\_data\-\_bit\-\_offset}
2415 \item \livelink{chap:DWATdatalocation}{DW\-\_AT\-\_data\-\_location}
2416 \item \livelink{chap:DWATdatamemberlocation}{DW\-\_AT\-\_data\-\_member\-\_location}
2417 \item \livelink{chap:DWATdecimalscale}{DW\-\_AT\-\_decimal\-\_scale}
2418 \item \livelink{chap:DWATdecimalsign}{DW\-\_AT\-\_decimal\-\_sign}
2419 \item \livelink{chap:DWATdefaultvalue}{DW\-\_AT\-\_default\-\_value}
2420 \item \livelink{chap:DWATdigitcount}{DW\-\_AT\-\_digit\-\_count}
2421 \item \livelink{chap:DWATdiscr}{DW\-\_AT\-\_discr}
2422 \item \livelink{chap:DWATdiscrlist}{DW\-\_AT\-\_discr\-\_list}
2423 \item \livelink{chap:DWATdiscrvalue}{DW\-\_AT\-\_discr\-\_value}
2424 \item \livelink{chap:DWATencoding}{DW\-\_AT\-\_encoding}
2425 \item \livelink{chap:DWATenumclass}{DW\-\_AT\-\_enum\-\_class}
2426 \item \livelink{chap:DWATendianity}{DW\-\_AT\-\_endianity}
2427 \item \livelink{chap:DWATexplicit}{DW\-\_AT\-\_explicit}
2428 \item \livelink{chap:DWATisoptional}{DW\-\_AT\-\_is\-\_optional}
2429 \item \livelink{chap:DWATlocation}{DW\-\_AT\-\_location}
2430 \item \livelink{chap:DWATlowerbound}{DW\-\_AT\-\_lower\-\_bound}
2431 \item \livelink{chap:DWATmutable}{DW\-\_AT\-\_mutable}
2432 \item \livelink{chap:DWATordering}{DW\-\_AT\-\_ordering}
2433 \item \livelink{chap:DWATpicturestring}{DW\-\_AT\-\_picture\-\_string}
2434 \item \livelink{chap:DWATprototyped}{DW\-\_AT\-\_prototyped}
2435 \item \livelink{chap:DWATsmall}{DW\-\_AT\-\_small}
2436 \item \livelink{chap:DWATsegment}{DW\-\_AT\-\_segment}
2437 \item \livelink{chap:DWATstringlength}{DW\-\_AT\-\_string\-\_length}
2438 \item \livelink{chap:DWATthreadsscaled}{DW\-\_AT\-\_threads\-\_scaled}
2439 \item \livelink{chap:DWATupperbound}{DW\-\_AT\-\_upper\-\_bound}
2440 \item \livelink{chap:DWATuselocation}{DW\-\_AT\-\_use\-\_location}
2441 \item \livelink{chap:DWATuseUTF8}{DW\-\_AT\-\_use\-\_UTF8}
2442 \item \livelink{chap:DWATvariableparameter}{DW\-\_AT\-\_variable\-\_parameter}
2443 \item \livelink{chap:DWATvirtuality}{DW\-\_AT\-\_virtuality}
2444 \item \livelink{chap:DWATvisibility}{DW\-\_AT\-\_visibility}
2445 \item \livelink{chap:DWATvtableelemlocation}{DW\-\_AT\-\_vtable\-\_elem\-\_location}
2448 Note that except for the initial
2449 \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute,
2450 \addtoindexx{name attribute}
2451 attributes are appended in order according to the alphabetical
2452 spelling of their identifier.
2454 If an implementation defines any vendor-specific attributes,
2455 any such attributes that are essential to the definition of
2456 the type should also be included at the end of the above list,
2457 in their own alphabetical suborder.
2459 An attribute that refers to another type entry T is processed
2460 as follows: (a) If T is in the list V at some V[x], use the
2461 letter 'R' as the marker and use the unsigned LEB128 encoding
2462 of x as the attribute value; otherwise, (b) use the letter 'T'
2463 as the marker, process the type T recursively by performing
2464 Steps 2 through 7, and use the result as the attribute value.
2466 Other attribute values use the letter 'A' as the marker, and
2467 the value consists of the form code (encoded as an unsigned
2468 LEB128 value) followed by the encoding of the value according
2469 to the form code. To ensure reproducibility of the signature,
2470 the set of forms used in the signature computation is limited
2471 to the following: \livelink{chap:DWFORMsdata}{DW\-\_FORM\-\_sdata},
2472 \livelink{chap:DWFORMflag}{DW\-\_FORM\-\_flag},
2473 \livelink{chap:DWFORMstring}{DW\-\_FORM\-\_string},
2474 and \livelink{chap:DWFORMblock}{DW\-\_FORM\-\_block}.
2476 \item If the tag in Step 3 is one of \livelink{chap:DWTAGpointertype}{DW\-\_TAG\-\_pointer\-\_type},
2477 \livelink{chap:DWTAGreferencetype}{DW\-\_TAG\-\_reference\-\_type},
2478 \livelink{chap:DWTAGrvaluereferencetype}{DW\-\_TAG\-\_rvalue\-\_reference\-\_type},
2479 \livelink{chap:DWTAGptrtomembertype}{DW\-\_TAG\-\_ptr\-\_to\-\_member\-\_type},
2480 or \livelink{chap:DWTAGfriend}{DW\-\_TAG\-\_friend}, and the referenced
2481 type (via the \livelink{chap:DWATtype}{DW\-\_AT\-\_type} or
2482 \livelink{chap:DWATfriend}{DW\-\_AT\-\_friend} attribute) has a
2483 \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute, append to S the letter 'N', the DWARF
2484 attribute code (\livelink{chap:DWATtype}{DW\-\_AT\-\_type} or
2485 \livelink{chap:DWATfriend}{DW\-\_AT\-\_friend}), the context of
2486 the type (according to the method in Step 2), the letter 'E',
2487 and the name of the type. For \livelink{chap:DWTAGfriend}{DW\-\_TAG\-\_friend}, if the referenced
2488 entry is a \livelink{chap:DWTAGsubprogram}{DW\-\_TAG\-\_subprogram}, the context is omitted and the
2489 name to be used is the ABI-specific name of the subprogram
2490 (e.g., the mangled linker name).
2493 \item 6.If the tag in Step 3 is not one of \livelink{chap:DWTAGpointertype}{DW\-\_TAG\-\_pointer\-\_type},
2494 \livelink{chap:DWTAGreferencetype}{DW\-\_TAG\-\_reference\-\_type},
2495 \livelink{chap:DWTAGrvaluereferencetype}{DW\-\_TAG\-\_rvalue\-\_reference\-\_type},
2496 \livelink{chap:DWTAGptrtomembertype}{DW\-\_TAG\-\_ptr\-\_to\-\_member\-\_type}, or
2497 \livelink{chap:DWTAGfriend}{DW\-\_TAG\-\_friend}, but has
2498 a \livelink{chap:DWATtype}{DW\-\_AT\-\_type} attribute, or if the referenced type (via
2499 the \livelink{chap:DWATtype}{DW\-\_AT\-\_type} or
2500 \livelink{chap:DWATfriend}{DW\-\_AT\-\_friend} attribute) does not have a
2501 \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute, the attribute is processed according to
2502 the method in Step 4 for an attribute that refers to another
2506 \item Visit each child C of the debugging information
2507 entry as follows: If C is a nested type entry or a member
2508 function entry, and has
2509 a \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute, append to
2510 \addtoindexx{name attribute}
2511 S the letter 'S', the tag of C, and its name; otherwise,
2512 process C recursively by performing Steps 3 through 7,
2513 appending the result to S. Following the last child (or if
2514 there are no children), append a zero byte.
2519 For the purposes of this algorithm, if a debugging information
2521 \livelink{chap:DWATspecification}{DW\-\_AT\-\_specification}
2522 attribute that refers to
2523 another entry D (which has a
2524 \livelink{chap:DWATdeclaration}{DW\-\_AT\-\_declaration}
2526 then S inherits the attributes and children of D, and S is
2527 processed as if those attributes and children were present in
2528 the entry S. Exception: if a particular attribute is found in
2529 both S and D, the attribute in S is used and the corresponding
2530 one in D is ignored.
2532 DWARF tag and attribute codes are appended to the sequence
2533 as unsigned LEB128 values, using the values defined earlier
2536 \textit{A grammar describing this computation may be found in
2537 Appendix \refersec{app:typesignaturecomputationgrammar}.
2540 \textit{An attribute that refers to another type entry should
2541 be recursively processed or replaced with the name of the
2542 referent (in Step 4, 5 or 6). If neither treatment applies to
2543 an attribute that references another type entry, the entry
2544 that contains that attribute should not be considered for a
2545 separate \addtoindex{type unit}.}
2547 \textit{If a debugging information entry contains an attribute from
2548 the list above that would require an unsupported form, that
2549 entry should not be considered for a separate
2550 \addtoindex{type unit}.}
2552 \textit{A type should be considered for a separate
2553 \addtoindex{type unit} only
2554 if all of the type entries that it contains or refers to in
2555 Steps 6 and 7 can themselves each be considered for a separate
2556 \addtoindex{type unit}.}
2558 Where the DWARF producer may reasonably choose two or more
2559 different forms for a given attribute, it should choose
2560 the simplest possible form in computing the signature. (For
2561 example, a constant value should be preferred to a location
2562 expression when possible.)
2564 Once the string S has been formed from the DWARF encoding,
2565 an \addtoindex{MD5 hash} is computed for the string and the lower 64 bits
2566 are taken as the type signature.
2568 \textit{The string S is intended to be a flattened representation of
2569 the type that uniquely identifies that type (i.e., a different
2570 type is highly unlikely to produce the same string).}
2572 \textit{A debugging information entry should not be placed in a
2573 separate \addtoindex{type unit}
2574 if any of the following apply:}
2578 \item \textit{The entry has an attribute whose value is a location
2579 expression, and the location expression contains a reference to
2580 another debugging information entry (e.g., a \livelink{chap:DWOPcallref}{DW\-\_OP\-\_call\-\_ref}
2581 operator), as it is unlikely that the entry will remain
2582 identical across compilation units.}
2584 \item \textit{The entry has an attribute whose value refers
2585 to a code location or a \addtoindex{location list}.}
2587 \item \textit{The entry has an attribute whose value refers
2588 to another debugging information entry that does not represent
2593 \textit{Certain attributes are not included in the type signature:}
2596 \item \textit{The \livelink{chap:DWATdeclaration}{DW\-\_AT\-\_declaration} attribute is not included because it
2597 indicates that the debugging information entry represents an
2598 incomplete declaration, and incomplete declarations should
2600 \addtoindexx{type unit}
2601 separate type units.}
2603 \item \textit{The \livelink{chap:DWATdescription}{DW\-\_AT\-\_description} attribute is not included because
2604 it does not provide any information unique to the defining
2605 declaration of the type.}
2607 \item \textit{The \livelink{chap:DWATdeclfile}{DW\-\_AT\-\_decl\-\_file}, \livelink{chap:DWATdeclline}{DW\-\_AT\-\_decl\-\_line}, and
2608 \livelink{chap:DWATdeclcolumn}{DW\-\_AT\-\_decl\-\_column} attributes are not included because they
2609 may vary from one source file to the next, and would prevent
2610 two otherwise identical type declarations from producing the
2611 \addtoindexx{MD5 hash}