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:
156 \begin{enumerate}[1.]
157 \item In the 32\dash bit DWARF format, an
158 \addtoindex{initial length field}
160 \addtoindex{initial length field!encoding}
161 Section \refersec{datarep:initiallengthvalues})
162 is an unsigned 32\dash bit integer (which
163 must be less than 0xfffffff0); in the 64\dash bit DWARF format,
164 an \addtoindex{initial length field} is 96 bits in size,
167 \item The first 32\dash bits have the value 0xffffffff.
169 \item The following 64\dash bits contain the actual length
170 represented as an unsigned 64\dash bit integer.
173 \textit{This representation allows a DWARF consumer to dynamically
174 detect that a DWARF section contribution is using the 64\dash bit
175 format and to adapt its processing accordingly.}
177 \item Section offset and section length
178 \addtoindexx{section length!use in headers}
180 \addtoindexx{section offset!use in headers}
181 in the headers of DWARF sections (other
182 \addtoindex{initial length field}
184 \addtoindex{initial length}
185 fields) are listed following. In the 32\dash bit DWARF format these
186 are 32\dash bit unsigned integer values; in the 64\dash bit DWARF format,
188 \addtoindexx{section length!in .debug\_aranges header}
190 \addtoindexx{section length!in .debug\_pubnames header}
192 \addtoindexx{section length!in .debug\_pubtypes header}
193 unsigned integer values.
197 Section &Name & Role \\ \hline
198 \addtoindex{.debug\_ranges} & \addtoindex{debug\_info\_offset} & offset in \addtoindex{.debug\_info} \\
199 \addtoindex{.debug\_frame}/CIE & \addtoindex{CIE\_id} & CIE distinguished value \\
200 \addtoindex{.debug\_frame}/FDE & \addtoindex{CIE\_pointer} & offset in \addtoindex{.debug\_frame} \\
201 \addtoindex{.debug\_info} & \addtoindex{debug\_abbrev\_offset} & offset in \addtoindex{.debug\_abbrev} \\
202 \addtoindex{.debug\_line} & \addtoindex{header\_length} & length of header itself \\
203 \addtoindex{.debug\_pubnames} & \addtoindex{debug\_info\_offset} & offset in \addtoindex{.debug\_info} \\
204 & \addtoindex{debug\_info\_length} & length of \addtoindex{.debug\_info} \\
206 \addtoindex{.debug\_pubtypes} & \addtoindex{debug\_info\_offset} & offset in \addtoindex{.debug\_info} \\
207 & \addtoindex{debug\_info\_length} & length of \addtoindex{.debug\_info} \\
209 \addtoindex{.debug\_types} & \addtoindex{debug\_abbrev\_offset} & offset in \addtoindex{.debug\_info} \\
210 & \addtoindex{type\_offset} & offset in of \addtoindex{.debug\_types} \\
215 \textit{The CIE\_id field in a CIE structure must be 64 bits because
216 it overlays the CIE\_pointer in a FDE structure; this implicit
217 union must be accessed to distinguish whether a CIE or FDE is
218 present, consequently, these two fields must exactly overlay
219 each other (both offset and size).}
221 \item Within the body of the \addtoindex{.debug\_info} or \addtoindex{.debug\_types}
222 section, certain forms of attribute value depend on the choice
223 of DWARF format as follows. For the 32\dash bit DWARF format,
224 the value is a 32\dash bit unsigned integer; for the 64\dash bit DWARF
225 format, the value is a 64\dash bit unsigned integer.
228 Form & Role \\ \hline
229 \livelink{chap:DWFORMrefaddr}{DW\-\_FORM\-\_ref\-\_addr}& offset in \addtoindex{.debug\_info} \\
230 \livetarg{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}& offset in a section other than \addtoindex{.debug\_info} or \addtoindex{.debug\_str} \\
231 \livelink{chap:DWFORMstrp}{DW\-\_FORM\-\_strp}&offset in \addtoindex{.debug\_str} \\
232 \livelink{chap:DWOPcallref}{DW\-\_OP\-\_call\-\_ref}&offset in \addtoindex{.debug\_info} \\
236 \item Within the body of the \addtoindex{.debug\_pubnames} and
237 \addtoindex{.debug\_pubtypes}
238 sections, the representation of the first field
239 of each tuple (which represents an offset in the
240 \addtoindex{.debug\_info}
241 section) depends on the DWARF format as follows: in the
242 32\dash bit DWARF format, this field is a 32\dash bit unsigned integer;
243 in the 64\dash bit DWARF format, it is a 64\dash bit unsigned integer.
248 The 32\dash bit and 64\dash bit DWARF format conventions must not be
249 intermixed within a single compilation unit.
251 \textit{Attribute values and section header fields that represent
252 addresses in the target program are not affected by these
255 A DWARF consumer that supports the 64\dash bit DWARF format must
256 support executables in which some compilation units use the
257 32\dash bit format and others use the 64\dash bit format provided that
258 the combination links correctly (that is, provided that there
259 are no link\dash time errors due to truncation or overflow). (An
260 implementation is not required to guarantee detection and
261 reporting of all such errors.)
263 \textit{It is expected that DWARF producing compilers will not use
264 the 64\dash bit format by default. In most cases, the division of
265 even very large applications into a number of executable and
266 shared objects will suffice to assure that the DWARF sections
267 within each individual linked object are less than 4 GBytes
268 in size. However, for those cases where needed, the 64\dash bit
269 format allows the unusual case to be handled as well. Even
270 in this case, it is expected that only application supplied
271 objects will need to be compiled using the 64\dash bit format;
272 separate 32\dash bit format versions of system supplied shared
273 executable libraries can still be used.}
277 \section{Format of Debugging Information}
278 \label{datarep:formatofdebugginginformation}
280 For each compilation unit compiled with a DWARF producer,
281 a contribution is made to the \addtoindex{.debug\_info} section of
282 the object file. Each such contribution consists of a
283 compilation unit header
284 (see Section \refersec{datarep:compilationunitheader})
286 single \livelink{chap:DWTAGcompileunit}{DW\-\_TAG\-\_compile\-\_unit} or \livelink{chap:DWTAGpartialunit}{DW\-\_TAG\-\_partial\-\_unit} debugging
287 information entry, together with its children.
289 For each type defined in a compilation unit, a contribution may
290 be made to the \addtoindex{.debug\_types}
291 section of the object file. Each
292 such contribution consists of a
293 \addtoindex{type unit} header
294 (see Section \refersec{datarep:typeunitheader})
295 followed by a \livelink{chap:DWTAGtypeunit}{DW\-\_TAG\-\_type\-\_unit} entry, together with
298 Each debugging information entry begins with a code that
299 represents an entry in a separate
300 \addtoindex{abbreviations table}. This
301 code is followed directly by a series of attribute values.
303 The appropriate entry in the
304 \addtoindex{abbreviations table} guides the
305 interpretation of the information contained directly in the
306 \addtoindex{.debug\_info} or
307 \addtoindex{.debug\_types} section.
309 Multiple debugging information entries may share the same
310 abbreviation table entry. Each compilation unit is associated
311 with a particular abbreviation table, but multiple compilation
312 units may share the same table.
313 \subsection{Unit Headers}
314 \label{datarep:unitheaders}
316 \subsubsection{Compilation Unit Header}
317 \label{datarep:compilationunitheader}
319 \begin{enumerate}[1.]
321 \item unit\_length (initial length) \\
322 \addtoindexx{unit\_length}
323 A 4\dash byte or 12\dash byte
324 \addtoindexx{initial length}
325 unsigned integer representing the length
326 of the \addtoindex{.debug\_info}
327 contribution for that compilation unit,
328 not including the length field itself. In the 32\dash bit DWARF
329 format, this is a 4\dash byte unsigned integer (which must be less
330 than 0xfffffff0); in the 64\dash bit DWARF format, this consists
331 of the 4\dash byte value 0xffffffff followed by an 8\dash byte unsigned
332 integer that gives the actual length
333 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
335 \item version (\addtoindex{uhalf})
336 A 2\dash byte unsigned integer representing the version of the
337 DWARF information for the compilation unit\addtoindexx{version number!compilation unit}
338 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
339 The value in this field is 4.
341 \item \addtoindex{debug\_abbrev\_offset} (section offset) \\
343 \addtoindexx{section offset!in .debug\_info header}
344 4\dash byte or 8\dash byte unsigned offset into the
345 \addtoindex{.debug\_abbrev}
346 section. This offset associates the compilation unit with a
347 particular set of debugging information entry abbreviations. In
348 the 32\dash bit DWARF format, this is a 4\dash byte unsigned length;
349 in the 64\dash bit DWARF format, this is an 8\dash byte unsigned length
350 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
352 \item address\_size (\addtoindex{ubyte}) \\
353 A 1\dash byte unsigned integer representing the size in bytes of
354 \addtoindexx{address\_size}
355 an address on the target architecture. If the system uses
356 \addtoindexx{address space!segmented}
357 segmented addressing, this value represents the size of the
358 offset portion of an address.
365 \subsubsection{Type Unit Header}
366 \label{datarep:typeunitheader}
368 The header for the series of debugging information entries
369 contributing to the description of a type that has been
370 placed in its own \addtoindex{type unit}, within the
371 \addtoindex{.debug\_types} section,
372 consists of the following information:
374 \begin{enumerate}[1.]
376 \item unit\_length (initial length) \\
377 \addtoindexx{unit\_length}
378 A 4\dash byte or 12\dash byte unsigned integer
379 \addtoindexx{initial length}
380 representing the length
381 of the \addtoindex{.debug\_types} contribution for that compilation unit,
382 not including the length field itself. In the 32\dash bit DWARF
383 format, this is a 4\dash byte unsigned integer (which must be
384 less than 0xfffffff0); in the 64\dash bit DWARF format, this
385 consists of the 4\dash byte value 0xffffffff followed by an
386 8\dash byte unsigned integer that gives the actual length
387 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
389 \item version (\addtoindex{uhalf})
390 A 2\dash byte unsigned integer representing the version of the
391 DWARF information for the
392 compilation unit\addtoindexx{version number!type unit}
393 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
394 The value in this field is 4.
396 \item \addtoindex{debug\_abbrev\_offset} (section offset) \\
398 \addtoindexx{section offset!in .debug\_types header}
399 4\dash byte or 8\dash byte unsigned offset into the
400 \addtoindex{.debug\_abbrev}
401 section. This offset associates the compilation unit with a
402 particular set of debugging information entry abbreviations. In
403 the 32\dash bit DWARF format, this is a 4\dash byte unsigned length;
404 in the 64\dash bit DWARF format, this is an 8\dash byte unsigned length
405 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
407 \item address\_size (ubyte) \\
408 A 1\dash byte unsigned integer representing the size
409 \addtoindexx{size of an address}
411 \addtoindexx{address\_size}
412 an address on the target architecture. If the system uses
413 \addtoindexx{address space!segmented}
414 segmented addressing, this value represents the size of the
415 offset portion of an address.
418 \item type\_signature (8\dash byte unsigned integer) \\
419 \addtoindexx{type signature}
421 \addtoindexx{type\_signature}
422 64\dash bit unique signature of the type described in this type
425 \textit{An attribute that refers(using \livelink{chap:DWFORMrefsig8}{DW\-\_FORM\-\_ref\-\_sig8}) to
426 the primary type contained in
427 this \addtoindex{type unit} uses this value.}
430 \item type\_offset (section offset) \\
431 \addtoindexx{type\_offset}
432 A 4\dash byte or 8\dash byte unsigned offset
433 \addtoindexx{section offset!in .debug\_types header}
434 relative to the beginning
435 of the \addtoindex{type unit} header.
436 This offset refers to the debugging
437 information entry that describes the type. Because the type
438 may be nested inside a namespace or other structures, and may
439 contain references to other types that have not been placed in
440 separate type units, it is not necessarily either the first or
441 the only entry in the type unit. In the 32\dash bit DWARF format,
442 this is a 4\dash byte unsigned length; in the 64\dash bit DWARF format,
443 this is an 8\dash byte unsigned length
444 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
448 \subsection{Debugging Information Entry}
449 \label{datarep:debugginginformationentry}
451 Each debugging information entry begins with an unsigned LEB128
452 number containing the abbreviation code for the entry. This
453 code represents an entry within the abbreviations table
454 associated with the compilation unit containing this entry. The
455 abbreviation code is followed by a series of attribute values.
457 On some architectures, there are alignment constraints on
458 section boundaries. To make it easier to pad debugging
459 information sections to satisfy such constraints, the
460 abbreviation code 0 is reserved. Debugging information entries
461 consisting of only the abbreviation code 0 are considered
464 \subsection{Abbreviations Tables}
465 \label{datarep:abbreviationstables}
467 The abbreviations tables for all compilation units
468 are contained in a separate object file section called
469 \addtoindex{.debug\_abbrev}.
470 As mentioned before, multiple compilation
471 units may share the same abbreviations table.
473 The abbreviations table for a single compilation unit consists
474 of a series of abbreviation declarations. Each declaration
475 specifies the tag and attributes for a particular form of
476 debugging information entry. Each declaration begins with
477 an unsigned LEB128 number representing the abbreviation
478 code itself. It is this code that appears at the beginning
479 of a debugging information entry in the
480 \addtoindex{.debug\_info} or
481 \addtoindex{.debug\_types}
482 section. As described above, the abbreviation
483 code 0 is reserved for null debugging information entries. The
484 abbreviation code is followed by another unsigned LEB128
485 number that encodes the entry’s tag. The encodings for the
486 tag names are given in
487 Table \refersec{tab:tagencodings}.
489 Following the tag encoding is a 1\dash byte value that determines
490 whether a debugging information entry using this abbreviation
491 has child entries or not. If the value is
492 \livetarg{chap:DWCHILDRENyes}{DW\-\_CHILDREN\-\_yes},
493 the next physically succeeding entry of any debugging
494 information entry using this abbreviation is the first
495 child of that entry. If the 1\dash byte value following the
496 abbreviation’s tag encoding is
497 \livetarg{chap:DWCHILDRENno}{DW\-\_CHILDREN\-\_no}, the next
498 physically succeeding entry of any debugging information entry
499 using this abbreviation is a sibling of that entry. (Either
500 the first child or sibling entries may be null entries). The
501 encodings for the child determination byte are given in
502 Table \refersec{tab:childdeterminationencodings}
504 Section \refersec{chap:relationshipofdebugginginformationentries},
505 each chain of sibling entries is terminated by a null entry.)
507 Finally, the child encoding is followed by a series of
508 attribute specifications. Each attribute specification
509 consists of two parts. The first part is an unsigned LEB128
510 number representing the attribute’s name. The second part
511 is an unsigned LEB128 number representing the attribute’s
512 form. The series of attribute specifications ends with an
513 entry containing 0 for the name and 0 for the form.
516 \livetarg{chap:DWFORMindirect}{DW\-\_FORM\-\_indirect} is a special case. For
517 attributes with this form, the attribute value itself in the
518 \addtoindex{.debug\_info} or
519 \addtoindex{.debug\_types}
520 section begins with an unsigned
521 LEB128 number that represents its form. This allows producers
522 to choose forms for particular attributes
523 \addtoindexx{abbreviations table!dynamic forms in}
525 without having to add a new entry to the abbreviations table.
527 The abbreviations for a given compilation unit end with an
528 entry consisting of a 0 byte for the abbreviation code.
531 Appendix \refersec{app:compilationunitsandabbreviationstableexample}
532 for a depiction of the organization of the
533 debugging information.}
535 \subsection{Attribute Encodings}
536 \label{datarep:attributeencodings}
538 The encodings for the attribute names are given in
539 Table \refersec{tab:attributeencodings}.
541 The attribute form governs how the value of the attribute is
542 encoded. There are nine classes of form, listed below. Each
543 class is a set of forms which have related representations
544 and which are given a common interpretation according to the
545 attribute in which the form is used.
547 Form \livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}
549 \addtoindexx{rangelistptr class}
551 \addtoindexx{macptr class}
553 \addtoindexx{loclistptr class}
555 \addtoindexx{lineptr class}
556 namely \livelink{chap:lineptr}{lineptr},
557 \livelink{chap:loclistptr}{loclistptr},
558 \livelink{chap:macptr}{macptr} or
559 \livelink{chap:rangelistptr}{rangelistptr}; the list
560 of classes allowed by the applicable attribute in
561 Table \refersec{tab:attributeencodings}
562 determines the class of the form.
564 \textit{In DWARF V3 the forms \livelink{chap:DWFORMdata4}{DW\-\_FORM\-\_data4} and \livelink{chap:DWFORMdata8}{DW\-\_FORM\-\_data8} were
565 \addtoindexx{lineptr class}
567 \addtoindexx{rangelistptr class}
569 \addtoindexx{macptr class}
571 \addtoindexx{loclistptr class}
572 class constant \addtoindexx{constant class}
573 or one of the classes
574 \livelink{chap:lineptr}{lineptr},
575 \livelink{chap:loclistptr}{loclistptr},
576 \livelink{chap:macptr}{macptr} or
577 \livelink{chap:rangelistptr}{rangelistptr}, depending on context. In
579 \livelink{chap:DWFORMdata4}{DW\-\_FORM\-\_data4} and
580 \livelink{chap:DWFORMdata8}{DW\-\_FORM\-\_data8} are members of class
581 constant in all cases.
583 \livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset} replaces
584 their usage for the other classes.}
586 Each possible form belongs to one or more of the following classes:
589 \item \livelinki{chap:DWATaddressclass}{address}{address class} \\
590 Represented as an object of appropriate size to hold an
591 address on the target machine
592 (\livetarg{chap:DWFORMaddr}{DW\-\_FORM\-\_addr}).
594 encoded in the compilation unit header
595 (see Section \refersec{datarep:compilationunitheader}).
596 This address is relocatable in a relocatable object file and
597 is relocated in an executable file or shared object.
599 \item \livelink{chap:block}{block} \\
600 Blocks come in four forms:
602 \begin{myindentpara}{1cm}
603 A 1\dash byte length followed by 0 to 255 contiguous information
604 bytes (\livetarg{chap:DWFORMblock1}{DW\-\_FORM\-\_block1}).
607 \begin{myindentpara}{1cm}
608 A 2\dash byte length followed by 0 to 65,535 contiguous information
609 bytes (\livetarg{chap:DWFORMblock2}{DW\-\_FORM\-\_block2}).
613 \begin{myindentpara}{1cm}
614 A 4\dash byte length followed by 0 to 4,294,967,295 contiguous
615 information bytes (\livetarg{chap:DWFORMblock4}{DW\-\_FORM\-\_block4}).
619 \begin{myindentpara}{1cm}
620 An unsigned LEB128 length followed by the number of bytes
621 specified by the length (\livetarg{chap:DWFORMblock}{DW\-\_FORM\-\_block}).
624 In all forms, the length is the number of information bytes
625 that follow. The information bytes may contain any mixture
626 of relocated (or relocatable) addresses, references to other
627 debugging information entries or data bytes.
630 There are six forms of constants. There are fixed length
631 constant data forms for one, two, four and eight byte values
633 \livetarg{chap:DWFORMdata1}{DW\-\_FORM\-\_data1},
634 \livetarg{chap:DWFORMdata2}{DW\-\_FORM\-\_data2},
635 \livetarg{chap:DWFORMdata4}{DW\-\_FORM\-\_data4},
636 and \livetarg{chap:DWFORMdata8}{DW\-\_FORM\-\_data8}).
637 There are also variable length constant
638 data forms encoded using LEB128 numbers (see below). Both
639 signed (\livetarg{chap:DWFORMsdata}{DW\-\_FORM\-\_sdata}) and unsigned
640 (\livetarg{chap:DWFORMudata}{DW\-\_FORM\-\_udata}) variable
641 length constants are available
643 The data in \livelink{chap:DWFORMdata1}{DW\-\_FORM\-\_data1},
644 \livelink{chap:DWFORMdata2}{DW\-\_FORM\-\_data2},
645 \livelink{chap:DWFORMdata4}{DW\-\_FORM\-\_data4} and
646 \livelink{chap:DWFORMdata8}{DW\-\_FORM\-\_data8}
647 can be anything. Depending on context, it may
648 be a signed integer, an unsigned integer, a floating\dash point
649 constant, or anything else. A consumer must use context to
650 know how to interpret the bits, which if they are target
651 machine data (such as an integer or floating point constant)
652 will be in target machine byte\dash order.
654 \textit{If one of the \livetarg{chap:DWFORMdata}{DW\-\_FORM\-\_data}\textless n\textgreater
655 forms is used to represent a
656 signed or unsigned integer, it can be hard for a consumer
657 to discover the context necessary to determine which
658 interpretation is intended. Producers are therefore strongly
659 encouraged to use \livelink{chap:DWFORMsdata}{DW\-\_FORM\-\_sdata} or
660 \livelink{chap:DWFORMudata}{DW\-\_FORM\-\_udata} for signed and
661 unsigned integers respectively, rather than
662 \livelink{chap:DWFORMdata}{DW\-\_FORM\-\_data}\textless n\textgreater.}
665 \item \livelink{chap:exprloc}{exprloc} \\
666 This is an unsigned LEB128 length followed by the
667 number of information bytes specified by the length
668 (\livetarg{chap:DWFORMexprloc}{DW\-\_FORM\-\_exprloc}).
669 The information bytes contain a DWARF
671 (see Section \refersec{chap:dwarfexpressions})
672 or location description
673 (see Section \refersec{chap:locationdescriptions}).
675 \item \livelink{chap:flag}{flag} \\
676 A flag \addtoindexx{flag class}
677 is represented explicitly as a single byte of data
678 (\livetarg{chap:DWFORMflag}{DW\-\_FORM\-\_flag}) or
679 implicitly (\livetarg{chap:DWFORMflagpresent}{DW\-\_FORM\-\_flag\-\_present}).
681 first case, if the \nolink{flag} has value zero, it indicates the
682 absence of the attribute; if the \nolink{flag} has a non\dash zero value,
683 it indicates the presence of the attribute. In the second
684 case, the attribute is implicitly indicated as present, and
685 no value is encoded in the debugging information entry itself.
687 \item \livelink{chap:lineptr}{lineptr} \\
688 This is an offset into
689 \addtoindexx{section offset!in class lineptr value}
691 \addtoindex{.debug\_line} section
692 (\livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}).
693 It consists of an offset from the
695 \addtoindex{.debug\_line}
696 section to the first byte of
697 the data making up the line number list for the compilation
699 It is relocatable in a relocatable object file, and
700 relocated in an executable or shared object. In the 32\dash bit
701 DWARF format, this offset is a 4\dash byte unsigned value;
702 in the 64\dash bit DWARF format, it is an 8\dash byte unsigned value
703 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
706 \item \livelink{chap:loclistptr}{loclistptr} \\
707 This is an offset into the
708 \addtoindex{.debug\_loc}
710 (\livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}).
711 It consists of an offset from the
712 \addtoindexx{section offset!in class loclistptr value}
714 \addtoindex{.debug\_loc}
715 section to the first byte of
716 the data making up the
717 \addtoindex{location list} for the compilation
719 It is relocatable in a relocatable object file, and
720 relocated in an executable or shared object. In the 32\dash bit
721 DWARF format, this offset is a 4\dash byte unsigned value;
722 in the 64\dash bit DWARF format, it is an 8\dash byte unsigned value
723 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
726 \item \livelink{chap:macptr}{macptr} \\
728 \addtoindexx{section offset!in class macptr value}
730 \addtoindex{.debug\_macinfo} section
731 (\livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}). It consists of an offset from the
732 beginning of the \addtoindex{.debug\_macinfo}
733 section to the first byte of
734 the data making up the macro information list for the compilation
736 It is relocatable in a relocatable object file, and
737 relocated in an executable or shared object. In the 32\dash bit
738 DWARF format, this offset is a 4\dash byte unsigned value;
739 in the 64\dash bit DWARF format, it is an 8\dash byte unsigned value
740 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
742 \item \livelink{chap:rangelistptr}{rangelistptr} \\
744 \addtoindexx{section offset!in class rangelistptr value}
745 offset into the \addtoindex{.debug\_ranges} section
746 (\livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}).
748 offset from the beginning of the
749 \addtoindex{.debug\_ranges} section
750 to the beginning of the non\dash contiguous address ranges
751 information for the referencing entity.
753 a relocatable object file, and relocated in an executable or
754 shared object. In the 32\dash bit DWARF format, this offset
755 is a 4\dash byte unsigned value; in the 64\dash bit DWARF
756 format, it is an 8\dash byte unsigned value (see Section
757 \refersec{datarep:32bitand64bitdwarfformats}).
760 \textit{Because classes \livelink{chap:lineptr}{lineptr},
761 \livelink{chap:loclistptr}{loclistptr},
762 \livelink{chap:macptr}{macptr} and
763 \livelink{chap:rangelistptr}{rangelistptr}
764 share a common representation, it is not possible for an
765 attribute to allow more than one of these classes}
770 There are three types of reference.
773 \addtoindexx{reference class}
774 first type of reference can identify any debugging
775 information entry within the containing unit.
778 \addtoindexx{section offset!in class reference value}
779 offset from the first byte of the compilation
780 header for the compilation unit containing the reference. There
781 are five forms for this type of reference. There are fixed
782 length forms for one, two, four and eight byte offsets
783 (respectively, \livetarg{chap:DWFORMref1}{DW\-\_FORM\-\_ref1},
784 \livetarg{chap:DWFORMref2}{DW\-\_FORM\-\_ref2},
785 \livetarg{chap:DWFORMref4}{DW\-\_FORM\-\_ref4},
786 and \livetarg{chap:DWFORMref8}{DW\-\_FORM\-\_ref8}).
787 There is also an unsigned variable
788 length offset encoded form that uses unsigned LEB128 numbers
789 (\livetarg{chap:DWFORMrefudata}{DW\-\_FORM\-\_ref\-\_udata}).
790 Because this type of reference is within
791 the containing compilation unit no relocation of the value
794 The second type of reference can identify any debugging
795 information entry within a
796 \addtoindex{.debug\_info} section; in particular,
797 it may refer to an entry in a different compilation unit
798 from the unit containing the reference, and may refer to an
799 entry in a different shared object. This type of reference
800 (\livetarg{chap:DWFORMrefaddr}{DW\-\_FORM\-\_ref\-\_addr}) is an offset from the beginning of the
801 \addtoindex{.debug\_info}
802 section of the target executable or shared object;
803 it is relocatable in a relocatable object file and frequently
804 relocated in an executable file or shared object. For
805 references from one shared object or static executable file
806 to another, the relocation and identification of the target
807 object must be performed by the consumer. In the 32\dash bit DWARF
808 format, this offset is a 4\dash byte unsigned value;
809 in the 64\dash bit DWARF format, it is an 8\dash byte
811 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
813 \textit{A debugging information entry that may be referenced by
814 another compilation unit using \livelink{chap:DWFORMrefaddr}{DW\-\_FORM\-\_ref\-\_addr} must have a
815 global symbolic name.}
817 \textit{For a reference from one executable or shared object to
818 another, the reference is resolved by the debugger to identify
819 the shared object or executable and the offset into that
820 object’s \addtoindex{.debug\_info}
821 section in the same fashion as the run
822 time loader, either when the debug information is first read,
823 or when the reference is used.}
825 The third type of reference can identify any debugging
826 information type entry that has been placed in its own
827 \addtoindex{type unit}. This type of
828 reference (\livetarg{chap:DWFORMrefsig8}{DW\-\_FORM\-\_ref\-\_sig8}) is the
829 \addtoindexx{type signature}
830 64\dash bit type signature
831 (see Section \refersec{datarep:typesignaturecomputation})
835 \textit{The use of compilation unit relative references will reduce the
836 number of link\dash time relocations and so speed up linking. The
837 use of the second and third type of reference allows for the
838 sharing of information, such as types, across compilation
841 \textit{A reference to any kind of compilation unit identifies the
842 debugging information entry for that unit, not the preceding
846 A string is a sequence of contiguous non\dash null bytes followed by
848 \addtoindexx{string class}
849 A string may be represented immediately in the
850 debugging information entry itself
851 (\livetarg{chap:DWFORMstring}{DW\-\_FORM\-\_string}), or may
853 \addtoindexx{section offset!in class string value}
854 offset into a string table contained in
855 the \addtoindex{.debug\_str} section of the object file
856 (\livetarg{chap:DWFORMstrp}{DW\-\_FORM\-\_strp}). In
857 the 32\dash bit DWARF format, the representation of a
858 \livelink{chap:DWFORMstrp}{DW\-\_FORM\-\_strp}
859 value is a 4\dash byte unsigned offset; in the 64\dash bit DWARF format,
860 it is an 8\dash byte unsigned offset
861 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
863 If the \livelink{chap:DWATuseUTF8}{DW\-\_AT\-\_use\-\_UTF8}
864 \addtoindexx{use UTF8 attribute}\addtoindexx{UTF-8} attribute is specified for the
865 compilation unit entry, string values are encoded using the
866 UTF\dash 8 (\addtoindex{Unicode} Transformation Format\dash 8) from the Universal
867 Character Set standard (ISO/IEC 10646\dash 1:1993). Otherwise,
868 the string representation is unspecified.
870 \textit{The \addtoindex{Unicode} Standard Version 3 is fully compatible with
871 ISO/IEC 10646\dash 1:1993. It contains all the same characters
872 and encoding points as ISO/IEC 10646, as well as additional
873 information about the characters and their use.}
875 \textit{Earlier versions of DWARF did not specify the representation
876 of strings; for compatibility, this version also does
877 not. However, the UTF\dash 8 representation is strongly recommended.}
881 In no case does an attribute use
882 \addtoindexx{rangelistptr class}
884 \addtoindexx{loclistptr class}
886 \addtoindexx{lineptr class}
888 \addtoindexx{macptr class}
889 classes \livelink{chap:lineptr}{lineptr},
890 \livelink{chap:loclistptr}{loclistptr}, \livelink{chap:macptr}{macptr} or \livelink{chap:rangelistptr}{rangelistptr} to point into either the
891 \addtoindex{.debug\_info} or \addtoindex{.debug\_str} section.
893 The form encodings are listed in
894 Table \refersec{tab:attributeformencodings}.
897 \setlength{\extrarowheight}{0.1cm}
898 \begin{longtable}{l|l}
899 \caption{Tag encodings} \label{tab:tagencodings} \\
900 \hline \bfseries Tag name&\bfseries Value\\ \hline
902 \bfseries Tag name&\bfseries Value \\ \hline
904 \hline \emph{Continued on next page}
907 \ddag New in \addtoindex{DWARF Version 4}
909 \livelink{chap:DWTAGarraytype}{DW\-\_TAG\-\_array\-\_type} &0x01 \\
910 \livelink{chap:DWTAGclasstype}{DW\-\_TAG\-\_class\-\_type}&0x02 \\
911 \livelink{chap:DWTAGentrypoint}{DW\-\_TAG\-\_entry\-\_point}&0x03 \\
912 \livelink{chap:DWTAGenumerationtype}{DW\-\_TAG\-\_enumeration\-\_type}&0x04 \\
913 \livelink{chap:DWTAGformalparameter}{DW\-\_TAG\-\_formal\-\_parameter}&0x05 \\
914 \livelink{chap:DWTAGimporteddeclaration}{DW\-\_TAG\-\_imported\-\_declaration}&0x08 \\
915 \livelink{chap:DWTAGlabel}{DW\-\_TAG\-\_label}&0x0a \\
916 \livelink{chap:DWTAGlexicalblock}{DW\-\_TAG\-\_lexical\-\_block}&0x0b \\
917 \livelink{chap:DWTAGmember}{DW\-\_TAG\-\_member}&0x0d \\
918 \livelink{chap:DWTAGpointertype}{DW\-\_TAG\-\_pointer\-\_type}&0x0f \\
919 \livelink{chap:DWTAGreferencetype}{DW\-\_TAG\-\_reference\-\_type}&0x10 \\
920 \livelink{chap:DWTAGcompileunit}{DW\-\_TAG\-\_compile\-\_unit}&0x11 \\
921 \livelink{chap:DWTAGstringtype}{DW\-\_TAG\-\_string\-\_type}&0x12 \\
922 \livelink{chap:DWTAGstructuretype}{DW\-\_TAG\-\_structure\-\_type}&0x13 \\
923 \livelink{chap:DWTAGsubroutinetype}{DW\-\_TAG\-\_subroutine\-\_type}&0x15 \\
924 \livelink{chap:DWTAGtypedef}{DW\-\_TAG\-\_typedef}&0x16 \\
925 \livelink{chap:DWTAGuniontype}{DW\-\_TAG\-\_union\-\_type}&0x17 \\
926 \livelink{chap:DWTAGunspecifiedparameters}{DW\-\_TAG\-\_unspecified\-\_parameters}&0x18 \\
927 \livelink{chap:DWTAGvariant}{DW\-\_TAG\-\_variant}&0x19 \\
928 \livelink{chap:DWTAGcommonblock}{DW\-\_TAG\-\_common\-\_block}&0x1a \\
929 \livelink{chap:DWTAGcommoninclusion}{DW\-\_TAG\-\_common\-\_inclusion}&0x1b \\
930 \livelink{chap:DWTAGinheritance}{DW\-\_TAG\-\_inheritance}&0x1c \\
931 \livelink{chap:DWTAGinlinedsubroutine}{DW\-\_TAG\-\_inlined\-\_subroutine}&0x1d \\
932 \livelink{chap:DWTAGmodule}{DW\-\_TAG\-\_module}&0x1e \\
933 \livelink{chap:DWTAGptrtomembertype}{DW\-\_TAG\-\_ptr\-\_to\-\_member\-\_type}&0x1f \\
934 \livelink{chap:DWTAGsettype}{DW\-\_TAG\-\_set\-\_type}&0x20 \\
935 \livelink{chap:DWTAGsubrangetype}{DW\-\_TAG\-\_subrange\-\_type}&0x21 \\
936 \livelink{chap:DWTAGwithstmt}{DW\-\_TAG\-\_with\-\_stmt}&0x22 \\
937 \livelink{chap:DWTAGaccessdeclaration}{DW\-\_TAG\-\_access\-\_declaration}&0x23 \\
938 \livelink{chap:DWTAGbasetype}{DW\-\_TAG\-\_base\-\_type}&0x24 \\
939 \livelink{chap:DWTAGcatchblock}{DW\-\_TAG\-\_catch\-\_block}&0x25 \\
940 \livelink{chap:DWTAGconsttype}{DW\-\_TAG\-\_const\-\_type}&0x26 \\
941 \livelink{chap:DWTAGconstant}{DW\-\_TAG\-\_constant}&0x27 \\
942 \livelink{chap:DWTAGenumerator}{DW\-\_TAG\-\_enumerator}&0x28 \\
943 \livelink{chap:DWTAGfiletype}{DW\-\_TAG\-\_file\-\_type}&0x29 \\
944 \livelink{chap:DWTAGfriend}{DW\-\_TAG\-\_friend}&0x2a \\
945 \livelink{chap:DWTAGnamelist}{DW\-\_TAG\-\_namelist}&0x2b \\
946 \livelink{chap:DWTAGnamelistitem}{DW\-\_TAG\-\_namelist\-\_item}&0x2c \\
947 \livelink{chap:DWTAGpackedtype}{DW\-\_TAG\-\_packed\-\_type}&0x2d \\
948 \livelink{chap:DWTAGsubprogram}{DW\-\_TAG\-\_subprogram}&0x2e \\
949 \livelink{chap:DWTAGtemplatetypeparameter}{DW\-\_TAG\-\_template\-\_type\-\_parameter}&0x2f \\
950 \livelink{chap:DWTAGtemplatevalueparameter}{DW\-\_TAG\-\_template\-\_value\-\_parameter}&0x30 \\
951 \livelink{chap:DWTAGthrowntype}{DW\-\_TAG\-\_thrown\-\_type}&0x31 \\
952 \livelink{chap:DWTAGtryblock}{DW\-\_TAG\-\_try\-\_block}&0x32 \\
953 \livelink{chap:DWTAGvariantpart}{DW\-\_TAG\-\_variant\-\_part}&0x33 \\
954 \livelink{chap:DWTAGvariable}{DW\-\_TAG\-\_variable}&0x34 \\
955 \livelink{chap:DWTAGvolatiletype}{DW\-\_TAG\-\_volatile\-\_type}&0x35 \\
956 \livelink{chap:DWTAGdwarfprocedure}{DW\-\_TAG\-\_dwarf\-\_procedure}&0x36 \\
957 \livelink{chap:DWTAGrestricttype}{DW\-\_TAG\-\_restrict\-\_type}&0x37 \\
958 \livelink{chap:DWTAGinterfacetype}{DW\-\_TAG\-\_interface\-\_type}&0x38 \\
959 \livelink{chap:DWTAGnamespace}{DW\-\_TAG\-\_namespace}&0x39 \\
960 \livelink{chap:DWTAGimportedmodule}{DW\-\_TAG\-\_imported\-\_module}&0x3a \\
961 \livelink{chap:DWTAGunspecifiedtype}{DW\-\_TAG\-\_unspecified\-\_type}&0x3b \\
962 \livelink{chap:DWTAGpartialunit}{DW\-\_TAG\-\_partial\-\_unit}&0x3c \\
963 \livelink{chap:DWTAGimportedunit}{DW\-\_TAG\-\_imported\-\_unit}&0x3d \\
964 \livelink{chap:DWTAGcondition}{DW\-\_TAG\-\_condition}&0x3f \\
965 \livelink{chap:DWTAGsharedtype}{DW\-\_TAG\-\_shared\-\_type}&0x40 \\
966 \livelink{chap:DWTAGtypeunit}{DW\-\_TAG\-\_type\-\_unit} \ddag &0x41 \\
967 \livelink{chap:DWTAGrvaluereferencetype}{DW\-\_TAG\-\_rvalue\-\_reference\-\_type} \ddag &0x42 \\
968 \livelink{chap:DWTAGtemplatealias}{DW\-\_TAG\-\_template\-\_alias} \ddag &0x43 \\
969 \livelink{chap:DWTAGlouser}{DW\-\_TAG\-\_lo\-\_user}&0x4080 \\
970 \livelink{chap:DWTAGhiuser}{DW\-\_TAG\-\_hi\-\_user}&0xffff \\
976 \setlength{\extrarowheight}{0.1cm}
977 \begin{longtable}{l|l}
978 \caption{Child determination encodings}
979 \label{tab:childdeterminationencodings}
980 \addtoindexx{Child determination encodings} \\
981 \hline \bfseries Children determination name&\bfseries Value \\ \hline
983 \bfseries Children determination name&\bfseries Value \\ \hline
985 \hline \emph{Continued on next page}
989 \livelink{chap:DWCHILDRENno}{DW\-\_CHILDREN\-\_no}&0x00 \\
990 \livelink{chap:DWCHILDRENyes}{DW\-\_CHILDREN\-\_yes}&0x01 \\ \hline
995 \setlength{\extrarowheight}{0.1cm}
996 \begin{longtable}{l|l|l}
997 \caption{Attribute encodings}
998 \label{tab:attributeencodings}
999 \addtoindexx{attribute encodings} \\
1000 \hline \bfseries Attribute name&\bfseries Value &\bfseries Classes \\ \hline
1002 \bfseries Attribute name&\bfseries Value &\bfseries Classes\\ \hline
1004 \hline \emph{Continued on next page}
1007 \ddag New in \addtoindex{DWARF Version 4}
1009 \livelink{chap:DWATsibling}{DW\-\_AT\-\_sibling}&0x01&reference
1010 \addtoindexx{sibling attribute!encoding} \\
1011 \livelink{chap:DWATlocation}{DW\-\_AT\-\_location}&0x02&\livelink{chap:exprloc}{exprloc},
1012 \livelink{chap:loclistptr}{loclistptr}\addtoindex{location attribute!encoding} \\
1013 \livelink{chap:DWATname}{DW\-\_AT\-\_name}&0x03&string
1014 \addtoindexx{name attribute!encoding} \\
1015 \livelink{chap:DWATordering}{DW\-\_AT\-\_ordering}&0x09&constant
1016 \addtoindexx{ordering attribute!encoding} \\
1017 \livelink{chap:DWATbytesize}{DW\-\_AT\-\_byte\-\_size}&0x0b&constant, \livelink{chap:exprloc}{exprloc},
1018 reference \addtoindexx{byte size attribute!encoding} \\
1019 \livelink{chap:DWATbitoffset}{DW\-\_AT\-\_bit\-\_offset}&0x0c&constant,
1020 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{bit offset attribute!encoding} \\
1021 \livelink{chap:DWATbitsize}{DW\-\_AT\-\_bit\-\_size}&0x0d&constant,
1022 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{bit size attribute!encoding} \\
1023 \livelink{chap:DWATstmtlist}{DW\-\_AT\-\_stmt\-\_list}&0x10&\livelink{chap:lineptr}{lineptr}
1024 \addtoindex{statement list attribute!encoding} \\
1025 \livelink{chap:DWATlowpc}{DW\-\_AT\-\_low\-\_pc}&0x11&address
1026 \addtoindexx{low PC attribute!encoding} \\
1027 \livelink{chap:DWAThighpc}{DW\-\_AT\-\_high\-\_pc}&0x12&address, constant
1028 \addtoindexx{high PC attribute!encoding} \\
1029 \livelink{chap:DWATlanguage}{DW\-\_AT\-\_language}&0x13&constant
1030 \addtoindexx{language attribute!encoding} \\
1031 \livelink{chap:DWATdiscr}{DW\-\_AT\-\_discr}&0x15&reference
1032 \addtoindexx{discriminant attribute!encoding} \\
1033 \livelink{chap:DWATdiscrvalue}{DW\-\_AT\-\_discr\-\_value}&0x16&constant
1034 \addtoindexx{discriminant value attribute!encoding} \\
1035 \livelink{chap:DWATvisibility}{DW\-\_AT\-\_visibility}&0x17&constant
1036 \addtoindexx{visibility attribute!encoding} \\
1037 \livelink{chap:DWATimport}{DW\-\_AT\-\_import}&0x18&reference
1038 \addtoindexx{import attribute!encoding} \\
1039 \livelink{chap:DWATstringlength}{DW\-\_AT\-\_string\-\_length}&0x19&\livelink{chap:exprloc}{exprloc},
1040 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{string length attribute!encoding} \\
1041 \livelink{chap:DWATcommonreference}{DW\-\_AT\-\_common\-\_reference}&0x1a&reference
1042 \addtoindexx{common reference attribute!encoding} \\
1043 \livelink{chap:DWATcompdir}{DW\-\_AT\-\_comp\-\_dir}&0x1b&string
1044 \addtoindexx{compilation directory attribute!encoding} \\
1045 \livelink{chap:DWATconstvalue}{DW\-\_AT\-\_const\-\_value}&0x1c&\livelink{chap:block}{block}, constant, string
1046 \addtoindexx{constant value attribute!encoding} \\
1047 \livelink{chap:DWATcontainingtype}{DW\-\_AT\-\_containing\-\_type}&0x1d&reference
1048 \addtoindexx{containing type attribute!encoding} \\
1049 \livelink{chap:DWATdefaultvalue}{DW\-\_AT\-\_default\-\_value}&0x1e&reference
1050 \addtoindexx{default value attribute!encoding} \\
1051 \livelink{chap:DWATinline}{DW\-\_AT\-\_inline}&0x20&constant
1052 \addtoindexx{inline attribute!encoding} \\
1053 \livelink{chap:DWATisoptional}{DW\-\_AT\-\_is\-\_optional}&0x21&\livelink{chap:flag}{flag}
1054 \addtoindexx{is optional attribute!encoding} \\
1055 \livelink{chap:DWATlowerbound}{DW\-\_AT\-\_lower\-\_bound}&0x22&constant,
1056 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{lower bound attribute!encoding} \\
1057 \livelink{chap:DWATproducer}{DW\-\_AT\-\_producer}&0x25&string \addtoindexx{producer attribute!encoding} \\
1058 \livelink{chap:DWATprototyped}{DW\-\_AT\-\_prototyped}&0x27&\livelink{chap:flag}{flag}
1059 \addtoindexx{prototyped attribute!encoding} \\
1060 \livelink{chap:DWATreturnaddr}{DW\-\_AT\-\_return\-\_addr}&0x2a&\livelink{chap:exprloc}{exprloc},
1061 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{return address attribute!encoding} \\
1062 % FIXME: lower case , not Constant
1063 \livelink{chap:DWATstartscope}{DW\-\_AT\-\_start\-\_scope}&0x2c&Constant,
1064 \livelink{chap:rangelistptr}{rangelistptr} \addtoindexx{start scope attribute!encoding} \\
1065 \livelink{chap:DWATbitstride}{DW\-\_AT\-\_bit\-\_stride}&0x2e&constant,
1066 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{bit stride attribute!encoding} \\
1067 \livelink{chap:DWATupperbound}{DW\-\_AT\-\_upper\-\_bound}&0x2f&constant,
1068 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{upper bound attribute!encoding} \\
1069 \livelink{chap:DWATabstractorigin}{DW\-\_AT\-\_abstract\-\_origin}&0x31&reference
1070 \addtoindexx{abstract origin attribute!encoding} \\
1071 \livelink{chap:DWATaccessibility}{DW\-\_AT\-\_accessibility}&0x32&constant
1072 \addtoindexx{accessibility attribute!encoding} \\
1073 \livelink{chap:DWATaddressclass}{DW\-\_AT\-\_address\-\_class}&0x33&constant
1074 \addtoindexx{address class attribute!encoding} \\
1075 \livelink{chap:DWATartificial}{DW\-\_AT\-\_artificial}&0x34&\livelink{chap:flag}{flag}
1076 \addtoindexx{artificial attribute!encoding} \\
1077 \livelink{chap:DWATbasetypes}{DW\-\_AT\-\_base\-\_types}&0x35&reference
1078 \addtoindexx{base types attribute!encoding} \\
1079 \livelink{chap:DWATcallingconvention}{DW\-\_AT\-\_calling\-\_convention}&0x36&constant
1080 \addtoindexx{calling convention attribute!encoding} \\
1081 \livelink{chap:DWATcount}{DW\-\_AT\-\_count}&0x37&constant, \livelink{chap:exprloc}{exprloc}, reference
1082 \addtoindexx{count attribute!encoding} \\
1083 \livelink{chap:DWATdatamemberlocation}{DW\-\_AT\-\_data\-\_member\-\_location}&0x38&constant,
1084 \livelink{chap:exprloc}{exprloc}, \livelink{chap:loclistptr}{loclistptr}
1085 \addtoindexx{data member attribute!encoding} \\
1086 \livelink{chap:DWATdeclcolumn}{DW\-\_AT\-\_decl\-\_column}&0x39&constant
1087 \addtoindexx{declaration column attribute!encoding} \\
1088 \livelink{chap:DWATdeclfile}{DW\-\_AT\-\_decl\-\_file}&0x3a&constant
1089 \addtoindexx{declaration file attribute!encoding} \\
1090 \livelink{chap:DWATdeclline}{DW\-\_AT\-\_decl\-\_line}&0x3b&constant
1091 \addtoindexx{declaration line attribute!encoding} \\
1092 \livelink{chap:DWATdeclaration}{DW\-\_AT\-\_declaration}&0x3c&\livelink{chap:flag}{flag}
1093 \addtoindexx{declaration attribute!encoding} \\
1094 \livelink{chap:DWATdiscrlist}{DW\-\_AT\-\_discr\-\_list}&0x3d&\livelink{chap:block}{block}
1095 \addtoindexx{discriminant list attribute!encoding} \\
1096 \livelink{chap:DWATencoding}{DW\-\_AT\-\_encoding}&0x3e&constant
1097 \addtoindexx{encoding attribute!encoding} \\
1098 \livelink{chap:DWATexternal}{DW\-\_AT\-\_external}&0x3f&\livelink{chap:flag}{flag}
1099 \addtoindexx{external attribute!encoding} \\
1100 \livelink{chap:DWATframebase}{DW\-\_AT\-\_frame\-\_base}&0x40&\livelink{chap:exprloc}{exprloc},
1101 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{frame base attribute!encoding} \\
1102 \livelink{chap:DWATfriend}{DW\-\_AT\-\_friend}&0x41&reference
1103 \addtoindexx{friend attribute!encoding} \\
1104 \livelink{chap:DWATidentifiercase}{DW\-\_AT\-\_identifier\-\_case}&0x42&constant
1105 \addtoindexx{identifier case attribute!encoding} \\
1106 \livelink{chap:DWATmacroinfo}{DW\-\_AT\-\_macro\-\_info}&0x43&\livelink{chap:macptr}{macptr}
1107 \addtoindexx{macro information attribute!encoding} \\
1108 \livelink{chap:DWATnamelistitem}{DW\-\_AT\-\_namelist\-\_item}&0x44&reference
1109 \addtoindexx{name list item attribute!encoding} \\
1110 \livelink{chap:DWATpriority}{DW\-\_AT\-\_priority}&0x45&reference
1111 \addtoindexx{priority attribute!encoding} \\
1112 \livelink{chap:DWATsegment}{DW\-\_AT\-\_segment}&0x46&\livelink{chap:exprloc}{exprloc},
1113 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{segment attribute!encoding} \\
1114 \livelink{chap:DWATspecification}{DW\-\_AT\-\_specification}&0x47&reference
1115 \addtoindexx{specification attribute!encoding} \\
1116 \livelink{chap:DWATstaticlink}{DW\-\_AT\-\_static\-\_link}&0x48&\livelink{chap:exprloc}{exprloc},
1117 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{static link attribute!encoding} \\
1118 \livelink{chap:DWATtype}{DW\-\_AT\-\_type}&0x49&reference
1119 \addtoindexx{type attribute!encoding} \\
1120 \livelink{chap:DWATuselocation}{DW\-\_AT\-\_use\-\_location}&0x4a&\livelink{chap:exprloc}{exprloc},
1121 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{location list attribute!encoding} \\
1122 \livelink{chap:DWATvariableparameter}{DW\-\_AT\-\_variable\-\_parameter}&0x4b&\livelink{chap:flag}{flag}
1123 \addtoindexx{variable parameter attribute!encoding} \\
1124 \livelink{chap:DWATvirtuality}{DW\-\_AT\-\_virtuality}&0x4c&constant
1125 \addtoindexx{virtuality attribute!encoding} \\
1126 \livelink{chap:DWATvtableelemlocation}{DW\-\_AT\-\_vtable\-\_elem\-\_location}&0x4d&\livelink{chap:exprloc}{exprloc},
1127 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{vtable element location attribute!encoding} \\
1129 \livelink{chap:DWATallocated}{DW\-\_AT\-\_allocated}&0x4e&constant, \livelink{chap:exprloc}{exprloc},
1130 reference \addtoindexx{allocated attribute!encoding} \\
1131 \livelink{chap:DWATassociated}{DW\-\_AT\-\_associated}&0x4f&constant, \livelink{chap:exprloc}{exprloc},
1132 reference \addtoindexx{associated attribute!encoding} \\
1133 \livelink{chap:DWATdatalocation}{DW\-\_AT\-\_data\-\_location}&0x50&\livelink{chap:exprloc}{exprloc}
1134 \addtoindexx{data location attribute!encoding} \\
1135 \livelink{chap:DWATbytestride}{DW\-\_AT\-\_byte\-\_stride}&0x51&constant, \livelink{chap:exprloc}{exprloc},
1136 reference \addtoindexx{byte stride attribute!encoding} \\
1137 \livelink{chap:DWATentrypc}{DW\-\_AT\-\_entry\-\_pc}&0x52&address
1138 \addtoindexx{entry pc attribute!encoding} \\
1139 \livelink{chap:DWATuseUTF8}{DW\-\_AT\-\_use\-\_UTF8}&0x53&\livelink{chap:flag}{flag}
1140 \addtoindexx{use UTF8 attribute!encoding}\addtoindex{UTF-8} \\
1141 \livelink{chap:DWATextension}{DW\-\_AT\-\_extension}&0x54&reference
1142 \addtoindexx{extension attribute!encoding} \\
1143 \livelink{chap:DWATranges}{DW\-\_AT\-\_ranges}&0x55&\livelink{chap:rangelistptr}{rangelistptr}
1144 \addtoindexx{ranges attribute!encoding} \\
1145 \livelink{chap:DWATtrampoline}{DW\-\_AT\-\_trampoline}&0x56&address, \livelink{chap:flag}{flag},
1146 reference, string \addtoindexx{trampoline attribute!encoding} \\
1147 \livelink{chap:DWATcallcolumn}{DW\-\_AT\-\_call\-\_column}&0x57&constant
1148 \addtoindexx{call column attribute!encoding} \\
1149 \livelink{chap:DWATcallfile}{DW\-\_AT\-\_call\-\_file}&0x58&constant
1150 \addtoindexx{call file attribute!encoding} \\
1151 \livelink{chap:DWATcallline}{DW\-\_AT\-\_call\-\_line}&0x59&constant
1152 \addtoindexx{call line attribute!encoding} \\
1153 \livelink{chap:DWATdescription}{DW\-\_AT\-\_description}&0x5a&string
1154 \addtoindexx{description attribute!encoding} \\
1155 \livelink{chap:DWATbinaryscale}{DW\-\_AT\-\_binary\-\_scale}&0x5b&constant
1156 \addtoindexx{binary scale attribute!encoding} \\
1157 \livelink{chap:DWATdecimalscale}{DW\-\_AT\-\_decimal\-\_scale}&0x5c&constant
1158 \addtoindexx{decimal scale attribute!encoding} \\
1159 \livelink{chap:DWATsmall}{DW\-\_AT\-\_small} &0x5d&reference
1160 \addtoindexx{small attribute!encoding} \\
1161 \livelink{chap:DWATdecimalsign}{DW\-\_AT\-\_decimal\-\_sign}&0x5e&constant
1162 \addtoindexx{decimal scale attribute!encoding} \\
1163 \livelink{chap:DWATdigitcount}{DW\-\_AT\-\_digit\-\_count}&0x5f&constant
1164 \addtoindexx{digit count attribute!encoding} \\
1165 \livelink{chap:DWATpicturestring}{DW\-\_AT\-\_picture\-\_string}&0x60&string
1166 \addtoindexx{picture string attribute!encoding} \\
1167 \livelink{chap:DWATmutable}{DW\-\_AT\-\_mutable}&0x61&\livelink{chap:flag}{flag}
1168 \addtoindexx{mutable attribute!encoding} \\
1170 \livelink{chap:DWATthreadsscaled}{DW\-\_AT\-\_threads\-\_scaled}&0x62&\livelink{chap:flag}{flag}
1171 \addtoindexx{thread scaled attribute!encoding} \\
1172 \livelink{chap:DWATexplicit}{DW\-\_AT\-\_explicit}&0x63&\livelink{chap:flag}{flag}
1173 \addtoindexx{explicit attribute!encoding} \\
1174 \livelink{chap:DWATobjectpointer}{DW\-\_AT\-\_object\-\_pointer}&0x64&reference
1175 \addtoindexx{object pointer attribute!encoding} \\
1176 \livelink{chap:DWATendianity}{DW\-\_AT\-\_endianity}&0x65&constant
1177 \addtoindexx{endianity attribute!encoding} \\
1178 \livelink{chap:DWATelemental}{DW\-\_AT\-\_elemental}&0x66&\livelink{chap:flag}{flag}
1179 \addtoindexx{elemental attribute!encoding} \\
1180 \livelink{chap:DWATpure}{DW\-\_AT\-\_pure}&0x67&\livelink{chap:flag}{flag}
1181 \addtoindexx{pure attribute!encoding} \\
1182 \livelink{chap:DWATrecursive}{DW\-\_AT\-\_recursive}&0x68&\livelink{chap:flag}{flag}
1183 \addtoindexx{recursive attribute!encoding} \\
1184 \livelink{chap:DWATsignature}{DW\-\_AT\-\_signature} \ddag &0x69&reference
1185 \addtoindexx{signature attribute!encoding} \\
1186 \livelink{chap:DWATmainsubprogram}{DW\-\_AT\-\_main\-\_subprogram} \ddag &0x6a&\livelink{chap:flag}{flag}
1187 \addtoindexx{main subprogram attribute!encoding} \\
1188 \livelink{chap:DWATdatabitoffset}{DW\-\_AT\-\_data\-\_bit\-\_offset} \ddag &0x6b&constant
1189 \addtoindexx{data bit offset attribute!encoding} \\
1190 \livelink{chap:DWATconstexpr}{DW\-\_AT\-\_const\-\_expr} \ddag &0x6c&\livelink{chap:flag}{flag}
1191 \addtoindexx{constant expression attribute!encoding} \\
1192 \livelink{chap:DWATenumclass}{DW\-\_AT\-\_enum\-\_class} \ddag &0x6d&\livelink{chap:flag}{flag}
1193 \addtoindexx{enumeration class attribute!encoding} \\
1194 \livelink{chap:DWATlinkagename}{DW\-\_AT\-\_linkage\-\_name} \ddag &0x6e&string
1195 \addtoindexx{linkage name attribute!encoding} \\
1196 \livetarg{chap:DWATlouser}{DW\-\_AT\-\_lo\-\_user}&0x2000 & --- \addtoindexx{low user attribute encoding} \\
1197 \livetarg{chap:DWAThiuser}{DW\-\_AT\-\_hi\-\_user}&0x3fff& --- \addtoindexx{high user attribute encoding} \\
1203 \setlength{\extrarowheight}{0.1cm}
1204 \begin{longtable}{l|l|l}
1205 \caption{Attribute form encodings} \label{tab:attributeformencodings} \\
1206 \hline \bfseries Form name&\bfseries Value &\bfseries Classes \\ \hline
1208 \bfseries Form name&\bfseries Value &\bfseries Classes\\ \hline
1210 \hline \emph{Continued on next page}
1213 \ddag New in \addtoindex{DWARF Version 4}
1215 \livelink{chap:DWFORMaddr}{DW\-\_FORM\-\_addr}&0x01&address \\
1216 \livelink{chap:DWFORMblock2}{DW\-\_FORM\-\_block2}&0x03&\livelink{chap:block}{block} \\
1217 \livelink{chap:DWFORMblock4}{DW\-\_FORM\-\_block4}&0x04&\livelink{chap:block}{block} \\
1218 \livelink{chap:DWFORMdata2}{DW\-\_FORM\-\_data2}&0x05&constant \\
1219 \livelink{chap:DWFORMdata4}{DW\-\_FORM\-\_data4}&0x06&constant \\
1220 \livelink{chap:DWFORMdata8}{DW\-\_FORM\-\_data8}&0x07&constant \\
1221 \livelink{chap:DWFORMstring}{DW\-\_FORM\-\_string}&0x08&string \\
1222 \livelink{chap:DWFORMblock}{DW\-\_FORM\-\_block}&0x09&\livelink{chap:block}{block} \\
1223 \livelink{chap:DWFORMblock1}{DW\-\_FORM\-\_block1}&0x0a&\livelink{chap:block}{block} \\
1224 \livelink{chap:DWFORMdata1}{DW\-\_FORM\-\_data1}&0x0b&constant \\
1225 \livelink{chap:DWFORMflag}{DW\-\_FORM\-\_flag}&0x0c&\livelink{chap:flag}{flag} \\
1226 \livelink{chap:DWFORMsdata}{DW\-\_FORM\-\_sdata}&0x0d&constant \\
1227 \livelink{chap:DWFORMstrp}{DW\-\_FORM\-\_strp}&0x0e&string \\
1228 \livelink{chap:DWFORMudata}{DW\-\_FORM\-\_udata}&0x0f&constant \\
1229 \livelink{chap:DWFORMrefaddr}{DW\-\_FORM\-\_ref\-\_addr}&0x10&reference \\
1230 \livelink{chap:DWFORMref1}{DW\-\_FORM\-\_ref1}&0x11&reference \\
1231 \livelink{chap:DWFORMref2}{DW\-\_FORM\-\_ref2}&0x12&reference \\
1232 \livelink{chap:DWFORMref4}{DW\-\_FORM\-\_ref4}&0x13&reference \\
1233 \livelink{chap:DWFORMref8}{DW\-\_FORM\-\_ref8}&0x14&reference \\
1234 \livelink{chap:DWFORMrefudata}{DW\-\_FORM\-\_ref\-\_udata}&0x15&reference \\
1235 \livelink{chap:DWFORMindirect}{DW\-\_FORM\-\_indirect}&0x16&(see Section \refersec{datarep:abbreviationstables}) \\
1236 \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} \\
1237 \livelink{chap:DWFORMexprloc}{DW\-\_FORM\-\_exprloc} \ddag &0x18&\livelink{chap:exprloc}{exprloc} \\
1238 \livelink{chap:DWFORMflagpresent}{DW\-\_FORM\-\_flag\-\_present} \ddag &0x19&\livelink{chap:flag}{flag} \\
1239 \livelink{chap:DWFORMrefsig8}{DW\-\_FORM\-\_ref\-\_sig8} \ddag &0x20&reference \\
1244 \section{Variable Length Data}
1245 \label{datarep:variablelengthdata}
1246 \addtoindexx{variable length data|see {LEB128}}
1248 \addtoindexx{Little Endian Base 128|see{LEB128}}
1249 encoded using ``Little Endian Base 128''
1250 \addtoindexx{little-endian encoding|see{endian attribute}}
1252 \addtoindexx{LEB128}
1253 LEB128 is a scheme for encoding integers
1254 densely that exploits the assumption that most integers are
1257 \textit{This encoding is equally suitable whether the target machine
1258 architecture represents data in big\dash\ endian or little\dash endian
1259 order. It is ``little\dash endian'' only in the sense that it
1260 avoids using space to represent the ``big'' end of an
1261 unsigned integer, when the big end is all zeroes or sign
1264 Unsigned LEB128 (ULEB128) numbers are encoded as follows:
1265 \addtoindexx{LEB128!unsigned, encoding as}
1266 start at the low order end of an unsigned integer and chop
1267 it into 7\dash bit chunks. Place each chunk into the low order 7
1268 bits of a byte. Typically, several of the high order bytes
1269 will be zero; discard them. Emit the remaining bytes in a
1270 stream, starting with the low order byte; set the high order
1271 bit on each byte except the last emitted byte. The high bit
1272 of zero on the last byte indicates to the decoder that it
1273 has encountered the last byte.
1275 The integer zero is a special case, consisting of a single
1278 Table \refersec{tab:examplesofunsignedleb128encodings}
1279 gives some examples of unsigned LEB128 numbers. The
1280 0x80 in each case is the high order bit of the byte, indicating
1281 that an additional byte follows.
1284 The encoding for signed, two’s complement LEB128 (SLEB128)
1285 \addtoindexx{LEB128!signed, encoding as}
1286 numbers is similar, except that the criterion for discarding
1287 high order bytes is not whether they are zero, but whether
1288 they consist entirely of sign extension bits. Consider the
1289 32\dash bit integer -2. The three high level bytes of the number
1290 are sign extension, thus LEB128 would represent it as a single
1291 byte containing the low order 7 bits, with the high order
1292 bit cleared to indicate the end of the byte stream. Note
1293 that there is nothing within the LEB128 representation that
1294 indicates whether an encoded number is signed or unsigned. The
1295 decoder must know what type of number to expect.
1296 Table \refersec{tab:examplesofunsignedleb128encodings}
1297 gives some examples of unsigned LEB128 numbers and
1298 Table \refersec{tab:examplesofsignedleb128encodings}
1299 gives some examples of signed LEB128
1302 \textit{Appendix \refersec{app:variablelengthdataencodingdecodinginformative}
1303 \addtoindexx{LEB128!examples}
1304 gives algorithms for encoding and decoding these forms.}
1308 \setlength{\extrarowheight}{0.1cm}
1309 \begin{longtable}{l|l|l}
1310 \caption{Examples of unsigned LEB128 encodings}
1311 \label{tab:examplesofunsignedleb128encodings}
1312 \addtoindexx{LEB128 encoding!examples} \\
1313 \hline \bfseries Number&\bfseries First byte &\bfseries Second byte \\ \hline
1315 \bfseries Number&\bfseries First Byte &\bfseries Second byte\\ \hline
1317 \hline \emph{Continued on next page}
1323 128& 0 + 0x80 & 1 \\
1324 129& 1 + 0x80 & 1 \\
1325 130& 2 + 0x80 & 1 \\
1326 12857& 57 + 0x80 & 100 \\
1333 \setlength{\extrarowheight}{0.1cm}
1334 \begin{longtable}{l|l|l}
1335 \caption{Examples of signed LEB128 encodings} \label{tab:examplesofsignedleb128encodings} \\
1336 \hline \bfseries Number&\bfseries First byte &\bfseries Second byte \\ \hline
1338 \bfseries Number&\bfseries First Byte &\bfseries Second byte\\ \hline
1340 \hline \emph{Continued on next page}
1346 127& 127 + 0x80 & 0 \\
1347 -127& 1 + 0x80 & 0x7f \\
1348 128& 0 + 0x80 & 1 \\
1349 -128& 0 + 0x80 & 0x7f \\
1350 129& 1 + 0x80 & 1 \\
1351 -129& -x7f + 0x80 & 0xtc \\
1358 \section{DWARF Expressions and Location Descriptions}
1359 \label{datarep:dwarfexpressionsandlocationdescriptions}
1360 \subsection{DWARF Expressions}
1361 \label{datarep:dwarfexpressions}
1364 \addtoindexx{DWARF Expression!operator encoding}
1365 DWARF expression is stored in a \nolink{block} of contiguous
1366 bytes. The bytes form a sequence of operations. Each operation
1367 is a 1\dash byte code that identifies that operation, followed by
1368 zero or more bytes of additional data. The encodings for the
1369 operations are described in
1370 Table \refersec{tab:dwarfoperationencodings}.
1373 \setlength{\extrarowheight}{0.1cm}
1374 \begin{longtable}{l|l|l|l}
1375 \caption{DWARF operation encodings} \label{tab:dwarfoperationencodings} \\
1376 \hline & &\bfseries No. of &\\
1377 \bfseries Operation&\bfseries Code &\bfseries Operands &\bfseries Notes\\ \hline
1379 & &\bfseries No. of &\\
1380 \bfseries Operation&\bfseries Code &\bfseries Operands &\bfseries Notes\\ \hline
1382 \hline \emph{Continued on next page}
1385 \ddag New in \addtoindex{DWARF Version 4}
1388 \livelink{chap:DWOPaddr}{DW\-\_OP\-\_addr}&0x03&1 & constant address \\
1389 & & &(size target specific) \\
1391 \livelink{chap:DWOPderef}{DW\-\_OP\-\_deref}&0x06&0 & \\
1394 \livelink{chap:DWOPconst1u}{DW\-\_OP\-\_const1u}&0x08&1&1\dash byte constant \\
1395 \livelink{chap:DWOPconst1s}{DW\-\_OP\-\_const1s}&0x09&1&1\dash byte constant \\
1396 \livelink{chap:DWOPconst2u}{DW\-\_OP\-\_const2u}&0x0a&1&2\dash byte constant \\
1397 \livelink{chap:DWOPconst2s}{DW\-\_OP\-\_const2s}&0x0b&1&2\dash byte constant \\
1398 \livelink{chap:DWOPconst4u}{DW\-\_OP\-\_const4u}&0x0c&1&4\dash byte constant \\
1399 \livelink{chap:DWOPconst4s}{DW\-\_OP\-\_const4s}&0x0d&1&4\dash byte constant \\
1400 \livelink{chap:DWOPconst8u}{DW\-\_OP\-\_const8u}&0x0e&1&8\dash byte constant \\
1401 \livelink{chap:DWOPconst8s}{DW\-\_OP\-\_const8s}&0x0f&1&8\dash byte constant \\
1402 \livelink{chap:DWOPconstu}{DW\-\_OP\-\_constu}&0x10&1&ULEB128 constant \\
1403 \livelink{chap:DWOPconsts}{DW\-\_OP\-\_consts}&0x11&1&SLEB128 constant \\
1404 \livelink{chap:DWOPdup}{DW\-\_OP\-\_dup}&0x12&0 & \\
1405 \livelink{chap:DWOPdrop}{DW\-\_OP\-\_drop}&0x13&0 & \\
1406 \livelink{chap:DWOPover}{DW\-\_OP\-\_over}&0x14&0 & \\
1407 \livelink{chap:DWOPpick}{DW\-\_OP\-\_pick}&0x15&1&1\dash byte stack index \\
1408 \livelink{chap:DWOPswap}{DW\-\_OP\-\_swap}&0x16&0 & \\
1409 \livelink{chap:DWOProt}{DW\-\_OP\-\_rot}&0x17&0 & \\
1410 \livelink{chap:DWOPxderef}{DW\-\_OP\-\_xderef}&0x18&0 & \\
1411 \livelink{chap:DWOPabs}{DW\-\_OP\-\_abs}&0x19&0 & \\
1412 \livelink{chap:DWOPand}{DW\-\_OP\-\_and}&0x1a&0 & \\
1413 \livelink{chap:DWOPdiv}{DW\-\_OP\-\_div}&0x1b&0 & \\
1417 \livelink{chap:DWOPminus}{DW\-\_OP\-\_minus}&0x1c&0 & \\
1418 \livelink{chap:DWOPmod}{DW\-\_OP\-\_mod}&0x1d&0 & \\
1419 \livelink{chap:DWOPmul}{DW\-\_OP\-\_mul}&0x1e&0 & \\
1420 \livelink{chap:DWOPneg}{DW\-\_OP\-\_neg}&0x1f&0 & \\
1421 \livelink{chap:DWOPnot}{DW\-\_OP\-\_not}&0x20&0 & \\
1422 \livelink{chap:DWOPor}{DW\-\_OP\-\_or}&0x21&0 & \\
1423 \livelink{chap:DWOPplus}{DW\-\_OP\-\_plus}&0x22&0 & \\
1424 \livelink{chap:DWOPplusuconst}{DW\-\_OP\-\_plus\-\_uconst}&0x23&1&ULEB128 addend \\
1425 \livelink{chap:DWOPshl}{DW\-\_OP\-\_shl}&0x24&0 & \\
1426 \livelink{chap:DWOPshr}{DW\-\_OP\-\_shr}&0x25&0 & \\
1427 \livelink{chap:DWOPshra}{DW\-\_OP\-\_shra}&0x26&0 & \\
1428 \livelink{chap:DWOPxor}{DW\-\_OP\-\_xor}&0x27&0 & \\
1429 \livelink{chap:DWOPskip}{DW\-\_OP\-\_skip}&0x2f&1&signed 2\dash byte constant \\
1430 \livelink{chap:DWOPbra}{DW\-\_OP\-\_bra}&0x28&1 & signed 2\dash byte constant \\
1431 \livelink{chap:DWOPeq}{DW\-\_OP\-\_eq}&0x29&0 & \\
1432 \livelink{chap:DWOPge}{DW\-\_OP\-\_ge}&0x2a&0 & \\
1433 \livelink{chap:DWOPgt}{DW\-\_OP\-\_gt}&0x2b&0 & \\
1434 \livelink{chap:DWOPle}{DW\-\_OP\-\_le}&0x2c&0 & \\
1435 \livelink{chap:DWOPlt}{DW\-\_OP\-\_lt}&0x2d&0 & \\
1436 \livelink{chap:DWOPne}{DW\-\_OP\-\_ne}&0x2e&0 & \\ \hline
1440 \livelink{chap:DWOPlit0}{DW\-\_OP\-\_lit0}&0x30 & 0 & \\
1442 \livelink{chap:DWOPlit1}{DW\-\_OP\-\_lit1}&0x31 & 0& literals 0 .. 31 = \\
1443 \ldots & & &\hspace{0.5cm}(\livelink{chap:DWOPlit0}{DW\-\_OP\-\_lit0} + literal) \\
1444 \livelink{chap:DWOPlit31}{DW\-\_OP\-\_lit31}&0x4f & 0 & \\ \hline
1446 \livelink{chap:DWOPreg0}{DW\-\_OP\-\_reg0} & 0x50 & 0 & \\
1447 \livelink{chap:DWOPreg1}{DW\-\_OP\-\_reg1} & 0x51 & 0® 0 .. 31 = \\
1448 \ldots & & &\hspace{0.5cm}(\livelink{chap:DWOPreg0}{DW\-\_OP\-\_reg0} + regnum) \\
1449 \livelink{chap:DWOPreg31}{DW\-\_OP\-\_reg31} & 0x6f & 0 & \\ \hline
1451 \livelink{chap:DWOPbreg0}{DW\-\_OP\-\_breg0} & 0x70 &1 & SLEB128 offset \\
1452 \livelink{chap:DWOPbreg1}{DW\-\_OP\-\_breg1} & 0x71 & 1 &base register 0 .. 31 = \\
1453 ... & & &\hspace{0.5cm}(\livelink{chap:DWOPbreg0}{DW\-\_OP\-\_breg0} + regnum) \\
1454 \livelink{chap:DWOPbreg31}{DW\-\_OP\-\_breg31} & 0x8f & 1 & \\ \hline
1456 \livelink{chap:DWOPregx}{DW\-\_OP\-\_regx} & 0x90 &1&ULEB128 register \\
1457 \livelink{chap:DWOPfbreg}{DW\-\_OP\-\_fbreg} & 0x91&1&SLEB128 offset \\
1458 \livelink{chap:DWOPbregx}{DW\-\_OP\-\_bregx} & 0x92&2 &ULEB128 register followed \\
1459 & & & by SLEB128 offset \\
1460 \livelink{chap:DWOPpiece}{DW\-\_OP\-\_piece} & 0x93 &1& ULEB128 size of piece addressed \\
1461 \livelink{chap:DWOPderefsize}{DW\-\_OP\-\_deref\-\_size} & 0x94 &1& 1-byte size of data retrieved \\
1462 \livelink{chap:DWOPxderefsize}{DW\-\_OP\-\_xderef\-\_size} & 0x95&1&1-byte size of data retrieved \\
1463 \livelink{chap:DWOPnop}{DW\-\_OP\-\_nop} & 0x96 &0& \\
1466 \livelink{chap:DWOPpushobjectaddress}{DW\-\_OP\-\_push\-\_object\-\_address}&0x97&0 & \\
1467 \livelink{chap:DWOPcall2}{DW\-\_OP\-\_call2}&0x98&1& 2\dash byte offset of DIE \\
1468 \livelink{chap:DWOPcall4}{DW\-\_OP\-\_call4}&0x99&1& 4\dash byte offset of DIE \\
1469 \livelink{chap:DWOPcallref}{DW\-\_OP\-\_call\-\_ref}&0x9a&1& 4\dash\ or 8\dash byte\\
1470 &&& offset of DIE \\
1471 \livelink{chap:DWOPformtlsaddress}{DW\-\_OP\-\_form\-\_tls\-\_address}&0x9b &0& \\
1472 \livelink{chap:DWOPcallframecfa}{DW\-\_OP\-\_call\-\_frame\-\_cfa} &0x9c &0& \\
1473 \livelink{chap:DWOPbitpiece}{DW\-\_OP\-\_bit\-\_piece}&0x9d &2&ULEB128 size followed by \\
1475 \livelink{chap:DWOPimplicitvalue}{DW\-\_OP\-\_implicit\-\_value} \ddag &0x9e &2&ULEB128 size followed by \\
1476 &&&\nolink{block} of that size\\
1477 \livelink{chap:DWOPstackvalue}{DW\-\_OP\-\_stack\-\_value} \ddag &0x9f &0& \\
1478 \livetarg{chap:DWOPlouser}{DW\-\_OP\-\_lo\-\_user} &0xe0 && \\
1479 \livetarg{chap:DWOPhiuser}{DW\-\_OP\-\_hi\-\_user} &0xff && \\
1485 \subsection{Location Descriptions}
1486 \label{datarep:locationdescriptions}
1488 A location description is used to compute the
1489 location of a variable or other entity.
1491 \subsection{Location Lists}
1492 \label{datarep:locationlists}
1494 Each entry in a \addtoindex{location list} is either a location list entry,
1495 a base address selection entry, or an
1496 \addtoindex{end of list entry!in location list}
1499 A \addtoindex{location list} entry consists of two address offsets followed
1500 by a 2\dash byte length, followed by a block of contiguous bytes
1501 that contains a DWARF location description. The length
1502 specifies the number of bytes in that block. The two offsets
1503 are the same size as an address on the target machine.
1505 A base address selection entry and an
1506 \addtoindex{end of list entry!in location list}
1507 end of list entry each
1508 consist of two (constant or relocated) address offsets. The two
1509 offsets are the same size as an address on the target machine.
1511 For a \addtoindex{location list} to be specified, the base address of
1512 \addtoindexx{base address selection entry!in location list}
1513 the corresponding compilation unit must be defined
1514 (see Section \refersec{chap:normalandpartialcompilationunitentries}).
1516 \section{Base Type Attribute Encodings}
1517 \label{datarep:basetypeattributeencodings}
1519 The encodings of the
1520 \hypertarget{chap:DWATencodingencodingofbasetype}
1522 \addtoindexx{encoding attribute!encoding}
1524 \livelink{chap:DWATencoding}{DW\-\_AT\-\_encoding}
1525 attribute are given in
1526 Table \refersec{tab:basetypeencodingvalues}
1529 \setlength{\extrarowheight}{0.1cm}
1530 \begin{longtable}{l|c}
1531 \caption{Base type encoding values} \label{tab:basetypeencodingvalues} \\
1532 \hline \bfseries Base type encoding code name&\bfseries Value \\ \hline
1534 \bfseries Base type encoding code name&\bfseries Value\\ \hline
1536 \hline \emph{Continued on next page}
1539 \ddag New in \addtoindex{DWARF Version 4}
1542 \livelink{chap:DWATEaddress}{DW\-\_ATE\-\_address}&0x01 \\
1543 \livelink{chap:DWATEboolean}{DW\-\_ATE\-\_boolean}&0x02 \\
1544 \livelink{chap:DWATEcomplexfloat}{DW\-\_ATE\-\_complex\-\_float}&0x03 \\
1545 \livelink{chap:DWATEfloat}{DW\-\_ATE\-\_float}&0x04 \\
1546 \livelink{chap:DWATEsigned}{DW\-\_ATE\-\_signed}&0x05 \\
1547 \livelink{chap:DWATEsignedchar}{DW\-\_ATE\-\_signed\-\_char}&0x06 \\
1548 \livelink{chap:DWATEunsigned}{DW\-\_ATE\-\_unsigned}&0x07 \\
1549 \livelink{chap:DWATEunsignedchar}{DW\-\_ATE\-\_unsigned\-\_char}&0x08 \\
1550 \livelink{chap:DWATEimaginaryfloat}{DW\-\_ATE\-\_imaginary\-\_float}&0x09 \\
1551 \livelink{chap:DWATEpackeddecimal}{DW\-\_ATE\-\_packed\-\_decimal}&0x0a \\
1552 \livelink{chap:DWATEnumericstring}{DW\-\_ATE\-\_numeric\-\_string}&0x0b \\
1553 \livelink{chap:DWATEedited}{DW\-\_ATE\-\_edited}&0x0c \\
1554 \livelink{chap:DWATEsignedfixed}{DW\-\_ATE\-\_signed\-\_fixed}&0x0d \\
1555 \livelink{chap:DWATEunsignedfixed}{DW\-\_ATE\-\_unsigned\-\_fixed}&0x0e \\
1556 \livelink{chap:DWATEdecimalfloat}{DW\-\_ATE\-\_decimal\-\_float} & 0x0f \\
1557 \livelink{chap:DWATEUTF}{DW\-\_ATE\-\_UTF} \ddag & 0x10 \\
1558 \livetarg{chap:DWATElouser}{DW\-\_ATE\-\_lo\-\_user} & 0x80 \\
1559 \livetarg{chap:DWATEhiuser}{DW\-\_ATE\-\_hi\-\_user} & 0xff \\
1565 The encodings of the constants used in the
1566 \livelink{chap:DWATdecimalsign}{DW\-\_AT\-\_decimal\-\_sign} attribute
1568 Table \refersec{tab:decimalsignencodings}.
1572 \setlength{\extrarowheight}{0.1cm}
1573 \begin{longtable}{l|c}
1574 \caption{Decimal sign encodings} \label{tab:decimalsignencodings} \\
1575 \hline \bfseries Decimal sign code name&\bfseries Value \\ \hline
1577 \bfseries Decimal sign code name&\bfseries Value\\ \hline
1579 \hline \emph{Continued on next page}
1584 \livelink{chap:DWDSunsigned}{DW\-\_DS\-\_unsigned} & 0x01 \\
1585 \livelink{chap:DWDSleadingoverpunch}{DW\-\_DS\-\_leading\-\_overpunch} & 0x02 \\
1586 \livelink{chap:DWDStrailingoverpunch}{DW\-\_DS\-\_trailing\-\_overpunch} & 0x03 \\
1587 \livelink{chap:DWDSleadingseparate}{DW\-\_DS\-\_leading\-\_separate} & 0x04 \\
1588 \livelink{chap:DWDStrailingseparate}{DW\-\_DS\-\_trailing\-\_separate} & 0x05 \\
1593 The encodings of the constants used in the
1594 \livelink{chap:DWATendianity}{DW\-\_AT\-\_endianity} attribute are given in
1595 Table \refersec{tab:endianityencodings}.
1598 \setlength{\extrarowheight}{0.1cm}
1599 \begin{longtable}{l|c}
1600 \caption{Endianity encodings} \label{tab:endianityencodings}\\
1601 \hline \bfseries Endian code name&\bfseries Value \\ \hline
1603 \bfseries Endian code name&\bfseries Value\\ \hline
1605 \hline \emph{Continued on next page}
1610 \livelink{chap:DWENDdefault}{DW\-\_END\-\_default} & 0x00 \\
1611 \livelink{chap:DWENDbig}{DW\-\_END\-\_big} & 0x01 \\
1612 \livelink{chap:DWENDlittle}{DW\-\_END\-\_little} & 0x02 \\
1613 \livetarg{chap:DWENDlouser}{DW\-\_END\-\_lo\-\_user} & 0x40 \\
1614 \livetarg{chap:DWENDhiuser}{DW\-\_END\-\_hi\-\_user} & 0xff \\
1619 \section{Accessibility Codes}
1620 \label{datarep:accessibilitycodes}
1621 The encodings of the constants used in the
1622 \livelink{chap:DWATaccessibility}{DW\-\_AT\-\_accessibility}
1624 \addtoindexx{accessibility attribute!encoding}
1626 Table \refersec{tab:accessibilityencodings}.
1629 \setlength{\extrarowheight}{0.1cm}
1630 \begin{longtable}{l|c}
1631 \caption{Accessibility encodings} \label{tab:accessibilityencodings}\\
1632 \hline \bfseries Accessibility code name&\bfseries Value \\ \hline
1634 \bfseries Accessibility code name&\bfseries Value\\ \hline
1636 \hline \emph{Continued on next page}
1641 \livelink{chap:DWACCESSpublic}{DW\-\_ACCESS\-\_public}&0x01 \\
1642 \livelink{chap:DWACCESSprotected}{DW\-\_ACCESS\-\_protected}&0x02 \\
1643 \livelink{chap:DWACCESSprivate}{DW\-\_ACCESS\-\_private}&0x03 \\
1649 \section{Visibility Codes}
1650 \label{datarep:visibilitycodes}
1651 The encodings of the constants used in the
1652 \livelink{chap:DWATvisibility}{DW\-\_AT\-\_visibility} attribute are given in
1653 Table \refersec{tab:visibilityencodings}.
1656 \setlength{\extrarowheight}{0.1cm}
1657 \begin{longtable}{l|c}
1658 \caption{Visibility encodings} \label{tab:visibilityencodings}\\
1659 \hline \bfseries Visiibility code name&\bfseries Value \\ \hline
1661 \bfseries Visibility code name&\bfseries Value\\ \hline
1663 \hline \emph{Continued on next page}
1668 \livelink{chap:DWVISlocal}{DW\-\_VIS\-\_local}&0x01 \\
1669 \livelink{chap:DWVISexported}{DW\-\_VIS\-\_exported}&0x02 \\
1670 \livelink{chap:DWVISqualified}{DW\-\_VIS\-\_qualified}&0x03 \\
1675 \section{Virtuality Codes}
1676 \label{datarep:vitualitycodes}
1678 The encodings of the constants used in the
1679 \livelink{chap:DWATvirtuality}{DW\-\_AT\-\_virtuality} attribute are given in
1680 Table \refersec{tab:virtualityencodings}.
1683 \setlength{\extrarowheight}{0.1cm}
1684 \begin{longtable}{l|c}
1685 \caption{Virtuality encodings} \label{tab:virtualityencodings}\\
1686 \hline \bfseries Virtuality code name&\bfseries Value \\ \hline
1688 \bfseries Virtuality code name&\bfseries Value\\ \hline
1690 \hline \emph{Continued on next page}
1695 \livelink{chap:DWVIRTUALITYnone}{DW\-\_VIRTUALITY\-\_none}&0x00 \\
1696 \livelink{chap:DWVIRTUALITYvirtual}{DW\-\_VIRTUALITY\-\_virtual}&0x01 \\
1697 \livelink{chap:DWVIRTUALITYpurevirtual}{DW\-\_VIRTUALITY\-\_pure\-\_virtual}&0x02 \\
1705 \livelink{chap:DWVIRTUALITYnone}{DW\-\_VIRTUALITY\-\_none} is equivalent to the absence of the
1706 \livelink{chap:DWATvirtuality}{DW\-\_AT\-\_virtuality}
1709 \section{Source Languages}
1710 \label{datarep:sourcelanguages}
1712 The encodings of the constants used
1713 \addtoindexx{language attribute, encoding}
1715 \addtoindexx{language name encoding}
1717 \livelink{chap:DWATlanguage}{DW\-\_AT\-\_language}
1718 attribute are given in
1719 Table \refersec{tab:languageencodings}.
1721 % If we don't force a following space it looks odd
1723 and their associated values are reserved, but the
1724 languages they represent are not well supported.
1725 Table \refersec{tab:languageencodings}
1727 \addtoindexx{lower bound attribute!default}
1728 default lower bound, if any, assumed for
1729 an omitted \livelink{chap:DWATlowerbound}{DW\-\_AT\-\_lower\-\_bound} attribute in the context of a
1730 \livelink{chap:DWTAGsubrangetype}{DW\-\_TAG\-\_subrange\-\_type} debugging information entry for each
1734 \setlength{\extrarowheight}{0.1cm}
1735 \begin{longtable}{l|c|c}
1736 \caption{Language encodings} \label{tab:languageencodings}\\
1737 \hline \bfseries Language name&\bfseries Value &\bfseries Default Lower Bound \\ \hline
1739 \bfseries Language name&\bfseries Value &\bfseries Default Lower Bound\\ \hline
1741 \hline \emph{Continued on next page}
1747 \livelink{chap:DWLANGC89}{DW\-\_LANG\-\_C89}&0x0001&0 \\
1748 \livelink{chap:DWLANGC}{DW\-\_LANG\-\_C}&0x0002&0 \\
1749 \livelink{chap:DWLANGAda83}{DW\-\_LANG\-\_Ada83} \dag &0x0003&1 \addtoindexx{Ada} \\
1750 \livelink{chap:DWLANGCplusplus}{DW\-\_LANG\-\_C\-\_plus\-\_plus} &0x0004&0 \\
1751 \livelink{chap:DWLANGCobol74}{DW\-\_LANG\-\_Cobol74} \dag &0x0005&1 \\
1752 \livelink{chap:DWLANGCobol85}{DW\-\_LANG\-\_Cobol85} \dag &0x0006&1 \\
1753 \livelink{chap:DWLANGFortran77}{DW\-\_LANG\-\_Fortran77}&0x0007&1 \\
1754 \livelink{chap:DWLANGFortran90}{DW\-\_LANG\-\_Fortran90}&0x0008&1 \\
1755 \livelink{chap:DWLANGPascal83}{DW\-\_LANG\-\_Pascal83}&0x0009&1 \\
1756 \livelink{chap:DWLANGModula2}{DW\-\_LANG\-\_Modula2}&0x000a&1 \\
1757 \livelink{chap:DWLANGJava}{DW\-\_LANG\-\_Java}&0x000b&0 \\
1758 \livelink{chap:DWLANGC99}{DW\-\_LANG\-\_C99}&0x000c&0 \\
1759 \livelink{chap:DWLANGAda95}{DW\-\_LANG\-\_Ada95} \dag &0x000d&1 \addtoindexx{Ada} \\
1760 \livelink{chap:DWLANGFortran95}{DW\-\_LANG\-\_Fortran95} &0x000e&1 \\
1761 \livelink{chap:DWLANGPLI}{DW\-\_LANG\-\_PLI} \dag &0x000f&1 \\
1762 \livelink{chap:DWLANGObjC}{DW\-\_LANG\-\_ObjC}&0x0010&0 \\
1763 \livelink{chap:DWLANGObjCplusplus}{DW\-\_LANG\-\_ObjC\-\_plus\-\_plus}&0x0011&0 \\
1764 \livelink{chap:DWLANGUPC}{DW\-\_LANG\-\_UPC}&0x0012&0 \\
1765 \livelink{chap:DWLANGD}{DW\-\_LANG\-\_D}&0x0013&0 \\
1766 \livelink{chap:DWLANGPython}{DW\-\_LANG\-\_Python} \dag &0x0014&0 \\
1767 \livetarg{chap:DWLANGlouser}{DW\-\_LANG\-\_lo\-\_user}&0x8000 & \\
1768 \livetarg{chap:DWLANGhiuser}{DW\-\_LANG\-\_hi\-\_user}&0xffff & \\
1773 \section{Address Class Encodings}
1774 \label{datarep:addressclassencodings}
1776 The value of the common
1777 \addtoindexi{address}{address class!attribute encoding}
1779 \livelink{chap:DWADDRnone}{DW\-\_ADDR\-\_none} is 0.
1782 \section{Identifier Case}
1783 \label{datarep:identifiercase}
1785 The encodings of the constants used in the
1786 \livelink{chap:DWATidentifiercase}{DW\-\_AT\-\_identifier\-\_case} attribute are given in
1787 Table \refersec{tab:identifiercaseencodings}.
1790 \setlength{\extrarowheight}{0.1cm}
1791 \begin{longtable}{l|c}
1792 \caption{Identifier case encodings} \label{tab:identifiercaseencodings}\\
1793 \hline \bfseries Identifier case name&\bfseries Value \\ \hline
1795 \bfseries Identifier case name&\bfseries Value\\ \hline
1797 \hline \emph{Continued on next page}
1801 \livelink{chap:DWIDcasesensitive}{DW\-\_ID\-\_case\-\_sensitive}&0x00 \\
1802 \livelink{chap:DWIDupcase}{DW\-\_ID\-\_up\-\_case}&0x01 \\
1803 \livelink{chap:DWIDdowncase}{DW\-\_ID\-\_down\-\_case}&0x02 \\
1804 \livelink{chap:DWIDcaseinsensitive}{DW\-\_ID\-\_case\-\_insensitive}&0x03 \\
1808 \section{Calling Convention Encodings}
1809 \label{datarep:callingconventionencodings}
1810 The encodings of the constants used in the
1811 \livelink{chap:DWATcallingconvention}{DW\-\_AT\-\_calling\-\_convention} attribute are given in
1812 Table \refersec{tab:callingconventionencodings}.
1815 \setlength{\extrarowheight}{0.1cm}
1816 \begin{longtable}{l|c}
1817 \caption{Calling convention encodings} \label{tab:callingconventionencodings}\\
1818 \hline \bfseries Calling Convention name&\bfseries Value \\ \hline
1820 \bfseries Calling Convention name&\bfseries Value\\ \hline
1822 \hline \emph{Continued on next page}
1827 \livelink{chap:DWCCnormal}{DW\-\_CC\-\_normal}&0x01 \\
1828 \livelink{chap:DWCCprogram}{DW\-\_CC\-\_program}&0x02 \\
1829 \livelink{chap:DWCCnocall}{DW\-\_CC\-\_nocall}&0x03 \\
1830 \livetarg{chap:DWCClouser}{DW\-\_CC\-\_lo\-\_user}&0x40 \\
1831 \livetarg{chap:DWCChiuser}{DW\-\_CC\-\_hi\-\_user}&0xff \\
1836 \section{Inline Codes}
1837 \label{datarep:inlinecodes}
1839 The encodings of the constants used in
1840 \addtoindexx{inline attribute!encoding}
1842 \livelink{chap:DWATinline}{DW\-\_AT\-\_inline} attribute are given in
1843 Table \refersec{tab:inlineencodings}.
1846 \setlength{\extrarowheight}{0.1cm}
1847 \begin{longtable}{l|c}
1848 \caption{Inline encodings} \label{tab:inlineencodings}\\
1849 \hline \bfseries Iline Code name&\bfseries Value \\ \hline
1851 \bfseries Iline Code name&\bfseries Value\\ \hline
1853 \hline \emph{Continued on next page}
1858 \livelink{chap:DWINLnotinlined}{DW\-\_INL\-\_not\-\_inlined}&0x00 \\
1859 \livelink{chap:DWINLinlined}{DW\-\_INL\-\_inlined}&0x01 \\
1860 \livelink{chap:DWINLdeclarednotinlined}{DW\-\_INL\-\_declared\-\_not\-\_inlined}&0x02 \\
1861 \livelink{chap:DWINLdeclaredinlined}{DW\-\_INL\-\_declared\-\_inlined}&0x03 \\
1866 % this clearpage is ugly, but the following table came
1867 % out oddly without it.
1869 \section{Array Ordering}
1870 \label{datarep:arrayordering}
1872 The encodings of the constants used in the
1873 \livelink{chap:DWATordering}{DW\-\_AT\-\_ordering} attribute are given in
1874 Table \refersec{tab:orderingencodings}.
1877 \setlength{\extrarowheight}{0.1cm}
1878 \begin{longtable}{l|c}
1879 \caption{Ordering encodings} \label{tab:orderingencodings}\\
1880 \hline \bfseries Ordering name&\bfseries Value \\ \hline
1882 \bfseries Ordering name&\bfseries Value\\ \hline
1884 \hline \emph{Continued on next page}
1889 \livelink{chap:DWORDrowmajor}{DW\-\_ORD\-\_row\-\_major}&0x00 \\
1890 \livelink{chap:DWORDcolmajor}{DW\-\_ORD\-\_col\-\_major}&0x01 \\
1896 \section{Discriminant Lists}
1897 \label{datarep:discriminantlists}
1899 The descriptors used in
1900 \addtoindexx{discriminant list attribute!encoding}
1902 \livelink{chap:DWATdiscrlist}{DW\-\_AT\-\_discr\-\_list} attribute are
1903 encoded as 1\dash byte constants. The
1904 defined values are given in
1905 Table \refersec{tab:discriminantdescriptorencodings}.
1907 % Odd that the 'Name' field capitalized here, it is not caps elsewhere.
1909 \setlength{\extrarowheight}{0.1cm}
1910 \begin{longtable}{l|c}
1911 \caption{Discriminant descriptor encodings} \label{tab:discriminantdescriptorencodings}\\
1912 \hline \bfseries Descriptor Name&\bfseries Value \\ \hline
1914 \bfseries Descriptor Name&\bfseries Value\\ \hline
1916 \hline \emph{Continued on next page}
1921 \livetarg{chap:DWDSClabel}{DW\-\_DSC\-\_label}&0x00 \\
1922 \livetarg{chap:DWDSCrange}{DW\-\_DSC\-\_range}&0x01 \\
1927 \section{Name Lookup Tables}
1928 \label{datarep:namelookuptables}
1930 Each set of entries in the table of global names contained
1931 in the \addtoindex{.debug\_pubnames} and
1932 \addtoindex{.debug\_pubtypes} sections begins
1933 with a header consisting of:
1936 \begin{enumerate}[1.]
1937 \item unit\_length (initial length) \\
1938 \addtoindexx{unit\_length}
1939 A 4\dash byte or 12\dash byte unsigned integer
1940 \addtoindexx{initial length}
1941 representing the length
1942 of the \addtoindex{.debug\_info}
1943 contribution for that compilation unit,
1944 not including the length field itself. In the 32\dash bit DWARF
1945 format, this is a 4\dash byte unsigned integer (which must be less
1946 than 0xfffffff0); in the 64\dash bit DWARF format, this consists
1947 of the 4\dash byte value 0xffffffff followed by an 8\dash byte unsigned
1948 integer that gives the actual length
1949 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
1951 \item version (\addtoindex{uhalf})
1952 A 2\dash byte unsigned integer representing the version of the
1953 DWARF information\addtoindexx{version number!compilation unit} for the compilation unit
1954 \addtoindexx{version number!name lookup table}
1955 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
1956 The value in this field is 4.
1958 % Some say unsigned offset this just says offset: FIXME
1959 \item \addtoindex{debug\_info\_offset} (section offset) \\
1961 \addtoindexx{section offset!in name lookup table set of entries}
1962 4\dash byte or 8\dash byte
1964 \addtoindex{.debug\_info}
1965 section of the compilation unit header.
1967 the 32\dash bit DWARF format, this is a 4\dash byte unsigned offset;
1968 in the 64\dash bit DWARF format, this is an 8\dash byte unsigned offsets
1969 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
1971 \item \addtoindex{debug\_info\_length} (section length) \\
1972 \addtoindexx{section length!in .debug\_pubnames header}
1974 \addtoindexx{section length!in .debug\_pubtypes header}
1975 4\dash byte or 8\dash byte length containing the size in bytes of the
1976 contents of the \addtoindex{.debug\_info}
1977 section generated to represent
1978 this compilation unit. In the 32\dash bit DWARF format, this is
1979 a 4\dash byte unsigned length; in the 64\dash bit DWARF format, this
1980 is an 8-byte unsigned length
1981 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
1986 This header is followed by a series of tuples. Each tuple
1987 consists of a 4\dash byte or 8\dash byte offset followed by a string
1988 of non\dash null bytes terminated by one null byte.
1990 DWARF format, this is a 4\dash byte offset; in the 64\dash bit DWARF
1991 format, it is an 8\dash byte offset.
1992 Each set is terminated by an
1993 offset containing the value 0.
1996 \section{Address Range Table}
1997 \label{datarep:addrssrangetable}
1999 Each set of entries in the table of address ranges contained
2000 in the \addtoindex{.debug\_aranges}
2001 section begins with a header containing:
2003 \begin{enumerate}[1.]
2004 % FIXME The unit length text is not fully consistent across
2007 \item unit\_length (initial length) \\
2008 \addtoindexx{unit\_length}
2009 A 4-byte or 12-byte length containing the length of the
2010 \addtoindexx{initial length}
2011 set of entries for this compilation unit, not including the
2012 length field itself. In the 32-bit DWARF format, this is a
2013 4-byte unsigned integer (which must be less than 0xfffffff0);
2014 in the 64-bit DWARF format, this consists of the 4-byte value
2015 0xffffffff followed by an 8-byte unsigned integer that gives
2017 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
2019 \item version (\addtoindex{uhalf}) \\
2020 A 2\dash byte version identifier
2021 \addtoindexx{version number!address range table} containing the value 2
2022 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
2024 \item debug\_info\_offset (section offset) \\
2026 \addtoindexx{section offset!in .debug\_aranges header}
2027 4\dash byte or 8\dash byte offset into the
2028 \addtoindex{.debug\_info} section of
2029 the compilation unit header. In the 32\dash bit DWARF format,
2030 this is a 4\dash byte unsigned offset; in the 64\dash bit DWARF format,
2031 this is an 8\dash byte unsigned offset
2032 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
2034 \item address\_size (ubyte) \\
2035 A 1\dash byte unsigned integer containing the size in bytes of an
2036 \addtoindexx{address\_size}
2038 \addtoindexx{size of an address}
2039 (or the offset portion of an address for segmented
2040 \addtoindexx{address space!segmented}
2041 addressing) on the target system.
2043 \item segment\_size (ubyte) \\
2045 \addtoindexx{segment\_size}
2046 1\dash byte unsigned integer containing the size in bytes of a
2047 segment selector on the target system.
2051 This header is followed by a series of tuples. Each tuple
2052 consists of a segment, an address and a length.
2054 size is given by the \addtoindex{segment\_size} field of the header; the
2055 address and length size are each given by the address\_size
2056 field of the header.
2057 The first tuple following the header in
2058 each set begins at an offset that is a multiple of the size
2059 of a single tuple (that is, the size of a segment selector
2060 plus twice the \addtoindex{size of an address}).
2061 The header is padded, if
2062 necessary, to that boundary. Each set of tuples is terminated
2063 by a 0 for the segment, a 0 for the address and 0 for the
2064 length. If the \addtoindex{segment\_size} field in the header is zero,
2065 the segment selectors are omitted from all tuples, including
2066 the terminating tuple.
2069 \section{Line Number Information}
2070 \label{datarep:linenumberinformation}
2072 The \addtoindexi{version number}{version number!line number information}
2073 in the line number program header is 4
2074 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
2076 The boolean values ``true'' and ``false''
2077 used by the line number information program are encoded
2078 as a single byte containing the value 0
2079 for ``false,'' and a non-zero value for ``true.''
2081 The encodings for the standard opcodes are given in
2082 \addtoindexx{line number opcodes!standard opcode encoding}
2083 Table \refersec{tab:linenumberstandardopcodeencodings}.
2085 % Odd that the 'Name' field capitalized here, it is not caps elsewhere.
2087 \setlength{\extrarowheight}{0.1cm}
2088 \begin{longtable}{l|c}
2089 \caption{Line Number Standard Opcode encodings} \label{tab:linenumberstandardopcodeencodings}\\
2090 \hline \bfseries Opcode Name&\bfseries Value \\ \hline
2092 \bfseries Opcode Name&\bfseries Value\\ \hline
2094 \hline \emph{Continued on next page}
2099 \livelink{chap:DWLNScopy}{DW\-\_LNS\-\_copy}&0x01 \\
2100 \livelink{chap:DWLNSadvancepc}{DW\-\_LNS\-\_advance\-\_pc}&0x02 \\
2101 \livelink{chap:DWLNSadvanceline}{DW\-\_LNS\-\_advance\-\_line}&0x03 \\
2102 \livelink{chap:DWLNSsetfile}{DW\-\_LNS\-\_set\-\_file}&0x04 \\
2103 \livelink{chap:DWLNSsetcolumn}{DW\-\_LNS\-\_set\-\_column}&0x05 \\
2104 \livelink{chap:DWLNSnegatestmt}{DW\-\_LNS\-\_negate\-\_stmt}&0x06 \\
2105 \livelink{chap:DWLNSsetbasicblock}{DW\-\_LNS\-\_set\-\_basic\-\_block}&0x07 \\
2106 \livelink{chap:DWLNSconstaddpc}{DW\-\_LNS\-\_const\-\_add\-\_pc}*0x08 \\
2107 \livelink{chap:DWLNSfixedadvancepc}{DW\-\_LNS\-\_fixed\-\_advance\-\_pc}&0x09 \\
2108 \livelink{chap:DWLNSsetprologueend}{DW\-\_LNS\-\_set\-\_prologue\-\_end}&0x0a \\
2109 \livelink{chap:DWLNSsetepiloguebegin}{DW\-\_LNS\-\_set\-\_epilogue\-\_begin}&0x0b \\
2110 \livelink{chap:DWLNSsetisa}{DW\-\_LNS\-\_set\-\_isa}&0x0c \\
2116 The encodings for the extended opcodes are given in
2117 \addtoindexx{line number opcodes!extended opcode encoding}
2118 Table \refersec{tab:linenumberextendedopcodeencodings}.
2121 \setlength{\extrarowheight}{0.1cm}
2122 \begin{longtable}{l|c}
2123 \caption{Line Number Extended Opcode encodings} \label{tab:linenumberextendedopcodeencodings}\\
2124 \hline \bfseries Opcode Name&\bfseries Value \\ \hline
2126 \bfseries Opcode Name&\bfseries Value\\ \hline
2128 \hline \emph{Continued on next page}
2131 \ddag New in \addtoindex{DWARF Version 4}
2134 \livelink{chap:DWLNEendsequence}{DW\-\_LNE\-\_end\-\_sequence}&0x01 \\
2135 \livelink{chap:DWLNEsetaddress}{DW\-\_LNE\-\_set\-\_address}&0x02\\
2136 \livelink{chap:DWLNEdefinefile}{DW\-\_LNE\-\_define\-\_file}&0x03\\
2137 \livelink{chap:DWLNEsetdiscriminator}{DW\-\_LNE\-\_set\-\_discriminator} \ddag &0x04 \\
2138 \livetarg{chap:DWLNElouser}{DW\-\_LNE\-\_lo\-\_user}&0x80 \\
2139 \livetarg{chap:DWLNEhiuser}{DW\-\_LNE\-\_hi\-\_user}&0xff \\
2144 \section{Macro Information}
2145 \label{datarep:macroinformation}
2147 The source line numbers and source file indices encoded in the
2148 macro information section are represented as unsigned LEB128
2149 numbers as are the constants in a
2150 \livelink{chap:DWMACINFOvendorext}{DW\-\_MACINFO\-\_vendor\-\_ext} entry.
2152 The macinfo type is encoded as a single byte.
2154 \addtoindexx{macinfo types!encoding}
2156 Table \refersec{tab:macinfotypeencodings}.
2160 \setlength{\extrarowheight}{0.1cm}
2161 \begin{longtable}{l|c}
2162 \caption{Macinfo Type Encodings} \label{tab:macinfotypeencodings}\\
2163 \hline \bfseries Macinfo Type Name&\bfseries Value \\ \hline
2165 \bfseries Macinfo Type Name&\bfseries Value\\ \hline
2167 \hline \emph{Continued on next page}
2172 \livelink{chap:DWMACINFOdefine}{DW\-\_MACINFO\-\_define}&0x01 \\
2173 \livelink{chap:DWMACINFOundef}{DW\-\_MACINFO\-\_undef}&0x02 \\
2174 \livelink{chap:DWMACINFOstartfile}{DW\-\_MACINFO\-\_start\-\_file}&0x03 \\
2175 \livelink{chap:DWMACINFOendfile}{DW\-\_MACINFO\-\_end\-\_file}&0x04 \\
2176 \livelink{chap:DWMACINFOvendorext}{DW\-\_MACINFO\-\_vendor\-\_ext}&0xff \\
2181 \section{Call Frame Information}
2182 \label{datarep:callframeinformation}
2184 In the 32\dash bit DWARF format, the value of the CIE id in the
2185 CIE header is 0xffffffff; in the 64\dash bit DWARF format, the
2186 value is 0xffffffffffffffff.
2188 The value of the CIE \addtoindexi{version number}{version number!call frame information}
2189 is 4 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
2191 Call frame instructions are encoded in one or more bytes. The
2192 primary opcode is encoded in the high order two bits of
2193 the first byte (that is, opcode = byte >> 6). An operand
2194 or extended opcode may be encoded in the low order 6
2195 bits. Additional operands are encoded in subsequent bytes.
2196 The instructions and their encodings are presented in
2197 Table \refersec{tab:callframeinstructionencodings}.
2200 \setlength{\extrarowheight}{0.1cm}
2201 \begin{longtable}{l|c|c|l|l}
2202 \caption{Call frame instruction encodings} \label{tab:callframeinstructionencodings} \\
2203 \hline &\bfseries High 2 &\bfseries Low 6 & & \\
2204 \bfseries Instruction&\bfseries Bits &\bfseries Bits &\bfseries Operand 1 &\bfseries Operand 2\\ \hline
2206 & \bfseries High 2 &\bfseries Low 6 & &\\
2207 \bfseries Instruction&\bfseries Bits &\bfseries Bits &\bfseries Operand 1 &\bfseries Operand 2\\ \hline
2209 \hline \emph{Continued on next page}
2214 \livelink{chap:DWCFAadvanceloc}{DW\-\_CFA\-\_advance\-\_loc}&0x1&delta & \\
2215 \livelink{chap:DWCFAoffset}{DW\-\_CFA\-\_offset}&0x2®ister&ULEB128 offset \\
2216 \livelink{chap:DWCFArestore}{DW\-\_CFA\-\_restore}&0x3®ister & & \\
2217 \livelink{chap:DWCFAnop}{DW\-\_CFA\-\_nop}&0&0 & & \\
2218 \livelink{chap:DWCFAsetloc}{DW\-\_CFA\-\_set\-\_loc}&0&0x01&address & \\
2219 \livelink{chap:DWCFAadvanceloc1}{DW\-\_CFA\-\_advance\-\_loc1}&0&0x02&1\dash byte delta & \\
2220 \livelink{chap:DWCFAadvanceloc2}{DW\-\_CFA\-\_advance\-\_loc2}&0&0x03&2\dash byte delta & \\
2221 \livelink{chap:DWCFAadvanceloc4}{DW\-\_CFA\-\_advance\-\_loc4}&0&0x04&4\dash byte delta & \\
2222 \livelink{chap:DWCFAoffsetextended}{DW\-\_CFA\-\_offset\-\_extended}&0&0x05&ULEB128 register&ULEB128 offset \\
2223 \livelink{chap:DWCFArestoreextended}{DW\-\_CFA\-\_restore\-\_extended}&0&0x06&ULEB128 register & \\
2224 \livelink{chap:DWCFAundefined}{DW\-\_CFA\-\_undefined}&0&0x07&ULEB128 register & \\
2225 \livelink{chap:DWCFAsamevalue}{DW\-\_CFA\-\_same\-\_value}&0&0x08 &ULEB128 register & \\
2226 \livelink{chap:DWCFAregister}{DW\-\_CFA\-\_register}&0&0x09&ULEB128 register &ULEB128 offset \\
2227 \livelink{chap:DWCFArememberstate}{DW\-\_CFA\-\_remember\-\_state}&0&0x0a & & \\
2228 \livelink{chap:DWCFArestorestate}{DW\-\_CFA\-\_restore\-\_state}&0&0x0b & & \\
2229 \livelink{chap:DWCFAdefcfa}{DW\-\_CFA\-\_def\-\_cfa}&0&0x0c &ULEB128 register&ULEB128 offset \\
2230 \livelink{chap:DWCFAdefcfaregister}{DW\-\_CFA\-\_def\-\_cfa\-\_register}&0&0x0d&ULEB128 register & \\
2231 \livelink{chap:DWCFAdefcfaoffset}{DW\-\_CFA\-\_def\-\_cfa\-\_offset}&0&0x0e &ULEB128 offset & \\
2232 \livelink{chap:DWCFAdefcfaexpression}{DW\-\_CFA\-\_def\-\_cfa\-\_expression}&0&0x0f &BLOCK \\
2233 \livelink{chap:DWCFAexpression}{DW\-\_CFA\-\_expression}&0&0x10&ULEB128 register & BLOCK \\
2235 \livelink{chap:DWCFAoffsetextendedsf}{DW\-\_CFA\-\_offset\-\_extended\-\_sf}&0&0x11&ULEB128 register&SLEB128 offset \\
2236 \livelink{chap:DWCFAdefcfasf}{DW\-\_CFA\-\_def\-\_cfa\-\_sf}&0&0x12&ULEB128 register&SLEB128 offset \\
2237 \livelink{chap:DWCFAdefcfaoffsetsf}{DW\-\_CFA\-\_def\-\_cfa\-\_offset\-\_sf}&0&0x13&SLEB128 offset & \\
2238 \livelink{chap:DWCFAvaloffset}{DW\-\_CFA\-\_val\-\_offset}&0&0x14&ULEB128&ULEB128 \\
2239 \livelink{chap:DWCFAvaloffsetsf}{DW\-\_CFA\-\_val\-\_offset\-\_sf}&0&0x15&ULEB128&SLEB128 \\
2240 \livelink{chap:DWCFAvalexpression}{DW\-\_CFA\-\_val\-\_expression}&0&0x16&ULEB128&BLOCK \\
2241 \livetarg{chap:DWCFAlouser}{DW\-\_CFA\-\_lo\-\_user}&0&0x1c & & \\
2242 \livetarg{chap:DWCFAhiuser}{DW\-\_CFA\-\_hi\-\_user}&0&0x3f & & \\
2246 \section{Non-contiguous Address Ranges}
2247 \label{datarep:noncontiguousaddressranges}
2249 Each entry in a \addtoindex{range list}
2250 (see Section \refersec{chap:noncontiguousaddressranges})
2252 \addtoindexx{base address selection entry!in range list}
2254 \addtoindexx{range list}
2255 a base address selection entry, or an end
2258 A \addtoindex{range list} entry consists of two relative addresses. The
2259 addresses are the same size as addresses on the target machine.
2261 A base address selection entry and an
2262 \addtoindex{end of list entry!in range list}
2263 end of list entry each
2264 \addtoindexx{base address selection entry!in range list}
2265 consist of two (constant or relocated) addresses. The two
2266 addresses are the same size as addresses on the target machine.
2268 For a \addtoindex{range list} to be specified, the base address of the
2269 \addtoindexx{base address selection entry!in range list}
2270 corresponding compilation unit must be defined
2271 (see Section \refersec{chap:normalandpartialcompilationunitentries}).
2274 \section{Dependencies and Constraints}
2275 \label{datarep:dependenciesandconstraints}
2277 The debugging information in this format is intended to
2279 \addtoindexx{DWARF section names!list of}
2281 the \addtoindex{.debug\_abbrev},
2282 \addtoindex{.debug\_aranges},
2283 \addtoindex{.debug\_frame},
2284 \addtoindex{.debug\_info},
2285 \addtoindex{.debug\_line},
2286 \addtoindex{.debug\_loc},
2287 \addtoindex{.debug\_macinfo},
2288 \addtoindex{.debug\_pubnames},
2289 \addtoindex{.debug\_pubtypes},
2290 \addtoindex{.debug\_ranges},
2291 \addtoindex{.debug\_str}
2293 \addtoindex{.debug\_types}
2294 sections of an object file, or equivalent
2295 separate file or database. The information is not
2296 word\dash aligned. Consequently: •
2299 \item For the 32\dash bit DWARF format and a target architecture with
2300 32\dash bit addresses, an assembler or compiler must provide a way
2301 to produce 2\dash byte and 4\dash byte quantities without alignment
2302 restrictions, and the linker must be able to relocate a
2303 4\dash byte address or
2304 \addtoindexx{section offset!alignment of}
2305 section offset that occurs at an arbitrary
2308 \item For the 32\dash bit DWARF format and a target architecture with
2309 64\dash bit addresses, an assembler or compiler must provide a
2310 way to produce 2\dash byte, 4\dash byte and 8\dash byte quantities without
2311 alignment restrictions, and the linker must be able to relocate
2312 an 8\dash byte address or 4\dash byte
2313 \addtoindexx{section offset!alignment of}
2314 section offset that occurs at an
2315 arbitrary alignment.
2317 \item For the 64\dash bit DWARF format and a target architecture with
2318 32\dash bit addresses, an assembler or compiler must provide a
2319 way to produce 2\dash byte, 4\dash byte and 8\dash byte quantities without
2320 alignment restrictions, and the linker must be able to relocate
2321 a 4\dash byte address or 8\dash byte
2322 \addtoindexx{section offset!alignment of}
2323 section offset that occurs at an
2324 arbitrary alignment.
2326 \textit{It is expected that this will be required only for very large
2327 32\dash bit programs or by those architectures which support
2328 a mix of 32\dash bit and 64\dash bit code and data within the same
2331 \item For the 64\dash bit DWARF format and a target architecture with
2332 64\dash bit addresses, an assembler or compiler must provide a
2333 way to produce 2\dash byte, 4\dash byte and 8\dash byte quantities without
2334 alignment restrictions, and the linker must be able to
2335 relocate an 8\dash byte address or
2336 \addtoindexx{section offset!alignment of}
2337 section offset that occurs at
2338 an arbitrary alignment.
2341 \section{Integer Representation Names}
2342 \label{datarep:integerrepresentationnames}
2344 The sizes of the integers used in the lookup by name, lookup
2345 by address, line number and call frame information sections
2347 Table 41 \refersec{tab:integerrepresentationnames}.
2350 \setlength{\extrarowheight}{0.1cm}
2351 \begin{longtable}{c|l}
2352 \caption{Integer Representation Names} \label{tab:integerrepresentationnames}\\
2353 \hline \bfseries Representation Name&\bfseries Representation \\ \hline
2355 \bfseries Representation Name&\bfseries Representation\\ \hline
2357 \hline \emph{Continued on next page}
2362 \addtoindex{sbyte}& signed, 1\dash byte integer \\
2363 \addtoindex{ubyte}&unsigned, 1\dash byte integer \\
2364 \addtoindex{uhalf}&unsigned, 2\dash byte integer \\
2365 \addtoindex{uword}&unsigned, 4\dash byte integer \\
2370 \section{Type Signature Computation}
2371 \label{datarep:typesignaturecomputation}
2373 A type signature is computed only by the DWARF producer;
2374 \addtoindexx{type signature computation}
2375 it is used by a DWARF consumer to resolve type references to
2376 the type definitions that are contained in
2377 \addtoindexx{type unit}
2380 The type signature for a type T0 is formed from the
2381 \addtoindex{MD5 hash}
2382 of a flattened description of the type. The flattened
2383 description of the type is a byte sequence derived from the
2384 DWARF encoding of the type as follows:
2386 \begin{enumerate}[1.]
2388 \item Start with an empty sequence S and a list V of visited
2389 types, where V is initialized to a list containing the type
2390 T0 as its single element. Elements in V are indexed from 1,
2393 \item If the debugging information entry represents a type that
2394 is nested inside another type or a namespace, append to S
2395 the type’s context as follows: For each surrounding type
2396 or namespace, beginning with the outermost such construct,
2397 append the letter 'C', the DWARF tag of the construct, and
2398 the name (taken from
2399 \addtoindexx{name attribute}
2400 the \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute) of the type
2401 \addtoindexx{name attribute}
2402 or namespace (including its trailing null byte).
2404 \item Append to S the letter 'D', followed by the DWARF tag of
2405 the debugging information entry.
2407 \item For each of the following attributes that are present in
2408 the debugging information entry, in the order listed below,
2409 append to S a marker letter (see below), the DWARF attribute
2410 code, and the attribute value.
2413 \item \livelink{chap:DWATname}{DW\-\_AT\-\_name}
2414 \item \livelink{chap:DWATaccessibility}{DW\-\_AT\-\_accessibility}
2415 \item \livelink{chap:DWATaddressclass}{DW\-\_AT\-\_address\-\_class}
2416 \item \livelink{chap:DWATallocated}{DW\-\_AT\-\_allocated}
2417 \item \livelink{chap:DWATartificial}{DW\-\_AT\-\_artificial}
2418 \item \livelink{chap:DWATassociated}{DW\-\_AT\-\_associated}
2419 \item \livelink{chap:DWATbinaryscale}{DW\-\_AT\-\_binary\-\_scale}
2420 \item \livelink{chap:DWATbitoffset}{DW\-\_AT\-\_bit\-\_offset}
2421 \item \livelink{chap:DWATbitsize}{DW\-\_AT\-\_bit\-\_size}
2422 \item \livelink{chap:DWATbitstride}{DW\-\_AT\-\_bit\-\_stride}
2423 \item \livelink{chap:DWATbytesize}{DW\-\_AT\-\_byte\-\_size}
2424 \item \livelink{chap:DWATbytestride}{DW\-\_AT\-\_byte\-\_stride}
2425 \item \livelink{chap:DWATconstexpr}{DW\-\_AT\-\_const\-\_expr}
2426 \item \livelink{chap:DWATconstvalue}{DW\-\_AT\-\_const\-\_value}
2427 \item \livelink{chap:DWATcontainingtype}{DW\-\_AT\-\_containing\-\_type}
2428 \item \livelink{chap:DWATcount}{DW\-\_AT\-\_count}
2429 \item \livelink{chap:DWATdatabitoffset}{DW\-\_AT\-\_data\-\_bit\-\_offset}
2430 \item \livelink{chap:DWATdatalocation}{DW\-\_AT\-\_data\-\_location}
2431 \item \livelink{chap:DWATdatamemberlocation}{DW\-\_AT\-\_data\-\_member\-\_location}
2432 \item \livelink{chap:DWATdecimalscale}{DW\-\_AT\-\_decimal\-\_scale}
2433 \item \livelink{chap:DWATdecimalsign}{DW\-\_AT\-\_decimal\-\_sign}
2434 \item \livelink{chap:DWATdefaultvalue}{DW\-\_AT\-\_default\-\_value}
2435 \item \livelink{chap:DWATdigitcount}{DW\-\_AT\-\_digit\-\_count}
2436 \item \livelink{chap:DWATdiscr}{DW\-\_AT\-\_discr}
2437 \item \livelink{chap:DWATdiscrlist}{DW\-\_AT\-\_discr\-\_list}
2438 \item \livelink{chap:DWATdiscrvalue}{DW\-\_AT\-\_discr\-\_value}
2439 \item \livelink{chap:DWATencoding}{DW\-\_AT\-\_encoding}
2440 \item \livelink{chap:DWATenumclass}{DW\-\_AT\-\_enum\-\_class}
2441 \item \livelink{chap:DWATendianity}{DW\-\_AT\-\_endianity}
2442 \item \livelink{chap:DWATexplicit}{DW\-\_AT\-\_explicit}
2443 \item \livelink{chap:DWATisoptional}{DW\-\_AT\-\_is\-\_optional}
2444 \item \livelink{chap:DWATlocation}{DW\-\_AT\-\_location}
2445 \item \livelink{chap:DWATlowerbound}{DW\-\_AT\-\_lower\-\_bound}
2446 \item \livelink{chap:DWATmutable}{DW\-\_AT\-\_mutable}
2447 \item \livelink{chap:DWATordering}{DW\-\_AT\-\_ordering}
2448 \item \livelink{chap:DWATpicturestring}{DW\-\_AT\-\_picture\-\_string}
2449 \item \livelink{chap:DWATprototyped}{DW\-\_AT\-\_prototyped}
2450 \item \livelink{chap:DWATsmall}{DW\-\_AT\-\_small}
2451 \item \livelink{chap:DWATsegment}{DW\-\_AT\-\_segment}
2452 \item \livelink{chap:DWATstringlength}{DW\-\_AT\-\_string\-\_length}
2453 \item \livelink{chap:DWATthreadsscaled}{DW\-\_AT\-\_threads\-\_scaled}
2454 \item \livelink{chap:DWATupperbound}{DW\-\_AT\-\_upper\-\_bound}
2455 \item \livelink{chap:DWATuselocation}{DW\-\_AT\-\_use\-\_location}
2456 \item \livelink{chap:DWATuseUTF8}{DW\-\_AT\-\_use\-\_UTF8}
2457 \item \livelink{chap:DWATvariableparameter}{DW\-\_AT\-\_variable\-\_parameter}
2458 \item \livelink{chap:DWATvirtuality}{DW\-\_AT\-\_virtuality}
2459 \item \livelink{chap:DWATvisibility}{DW\-\_AT\-\_visibility}
2460 \item \livelink{chap:DWATvtableelemlocation}{DW\-\_AT\-\_vtable\-\_elem\-\_location}
2463 Note that except for the initial
2464 \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute,
2465 \addtoindexx{name attribute}
2466 attributes are appended in order according to the alphabetical
2467 spelling of their identifier.
2469 If an implementation defines any vendor-specific attributes,
2470 any such attributes that are essential to the definition of
2471 the type should also be included at the end of the above list,
2472 in their own alphabetical suborder.
2474 An attribute that refers to another type entry T is processed
2475 as follows: (a) If T is in the list V at some V[x], use the
2476 letter 'R' as the marker and use the unsigned LEB128 encoding
2477 of x as the attribute value; otherwise, (b) use the letter 'T'
2478 as the marker, process the type T recursively by performing
2479 Steps 2 through 7, and use the result as the attribute value.
2481 Other attribute values use the letter 'A' as the marker, and
2482 the value consists of the form code (encoded as an unsigned
2483 LEB128 value) followed by the encoding of the value according
2484 to the form code. To ensure reproducibility of the signature,
2485 the set of forms used in the signature computation is limited
2486 to the following: \livelink{chap:DWFORMsdata}{DW\-\_FORM\-\_sdata},
2487 \livelink{chap:DWFORMflag}{DW\-\_FORM\-\_flag},
2488 \livelink{chap:DWFORMstring}{DW\-\_FORM\-\_string},
2489 and \livelink{chap:DWFORMblock}{DW\-\_FORM\-\_block}.
2491 \item If the tag in Step 3 is one of \livelink{chap:DWTAGpointertype}{DW\-\_TAG\-\_pointer\-\_type},
2492 \livelink{chap:DWTAGreferencetype}{DW\-\_TAG\-\_reference\-\_type},
2493 \livelink{chap:DWTAGrvaluereferencetype}{DW\-\_TAG\-\_rvalue\-\_reference\-\_type},
2494 \livelink{chap:DWTAGptrtomembertype}{DW\-\_TAG\-\_ptr\-\_to\-\_member\-\_type},
2495 or \livelink{chap:DWTAGfriend}{DW\-\_TAG\-\_friend}, and the referenced
2496 type (via the \livelink{chap:DWATtype}{DW\-\_AT\-\_type} or
2497 \livelink{chap:DWATfriend}{DW\-\_AT\-\_friend} attribute) has a
2498 \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute, append to S the letter 'N', the DWARF
2499 attribute code (\livelink{chap:DWATtype}{DW\-\_AT\-\_type} or
2500 \livelink{chap:DWATfriend}{DW\-\_AT\-\_friend}), the context of
2501 the type (according to the method in Step 2), the letter 'E',
2502 and the name of the type. For \livelink{chap:DWTAGfriend}{DW\-\_TAG\-\_friend}, if the referenced
2503 entry is a \livelink{chap:DWTAGsubprogram}{DW\-\_TAG\-\_subprogram}, the context is omitted and the
2504 name to be used is the ABI-specific name of the subprogram
2505 (e.g., the mangled linker name).
2508 \item 6.If the tag in Step 3 is not one of \livelink{chap:DWTAGpointertype}{DW\-\_TAG\-\_pointer\-\_type},
2509 \livelink{chap:DWTAGreferencetype}{DW\-\_TAG\-\_reference\-\_type},
2510 \livelink{chap:DWTAGrvaluereferencetype}{DW\-\_TAG\-\_rvalue\-\_reference\-\_type},
2511 \livelink{chap:DWTAGptrtomembertype}{DW\-\_TAG\-\_ptr\-\_to\-\_member\-\_type}, or
2512 \livelink{chap:DWTAGfriend}{DW\-\_TAG\-\_friend}, but has
2513 a \livelink{chap:DWATtype}{DW\-\_AT\-\_type} attribute, or if the referenced type (via
2514 the \livelink{chap:DWATtype}{DW\-\_AT\-\_type} or
2515 \livelink{chap:DWATfriend}{DW\-\_AT\-\_friend} attribute) does not have a
2516 \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute, the attribute is processed according to
2517 the method in Step 4 for an attribute that refers to another
2521 \item Visit each child C of the debugging information
2522 entry as follows: If C is a nested type entry or a member
2523 function entry, and has
2524 a \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute, append to
2525 \addtoindexx{name attribute}
2526 S the letter 'S', the tag of C, and its name; otherwise,
2527 process C recursively by performing Steps 3 through 7,
2528 appending the result to S. Following the last child (or if
2529 there are no children), append a zero byte.
2534 For the purposes of this algorithm, if a debugging information
2536 \livelink{chap:DWATspecification}{DW\-\_AT\-\_specification}
2537 attribute that refers to
2538 another entry D (which has a
2539 \livelink{chap:DWATdeclaration}{DW\-\_AT\-\_declaration}
2541 then S inherits the attributes and children of D, and S is
2542 processed as if those attributes and children were present in
2543 the entry S. Exception: if a particular attribute is found in
2544 both S and D, the attribute in S is used and the corresponding
2545 one in D is ignored.
2547 DWARF tag and attribute codes are appended to the sequence
2548 as unsigned LEB128 values, using the values defined earlier
2551 \textit{A grammar describing this computation may be found in
2552 Appendix \refersec{app:typesignaturecomputationgrammar}.
2555 \textit{An attribute that refers to another type entry should
2556 be recursively processed or replaced with the name of the
2557 referent (in Step 4, 5 or 6). If neither treatment applies to
2558 an attribute that references another type entry, the entry
2559 that contains that attribute should not be considered for a
2560 separate \addtoindex{type unit}.}
2562 \textit{If a debugging information entry contains an attribute from
2563 the list above that would require an unsupported form, that
2564 entry should not be considered for a separate
2565 \addtoindex{type unit}.}
2567 \textit{A type should be considered for a separate
2568 \addtoindex{type unit} only
2569 if all of the type entries that it contains or refers to in
2570 Steps 6 and 7 can themselves each be considered for a separate
2571 \addtoindex{type unit}.}
2573 Where the DWARF producer may reasonably choose two or more
2574 different forms for a given attribute, it should choose
2575 the simplest possible form in computing the signature. (For
2576 example, a constant value should be preferred to a location
2577 expression when possible.)
2579 Once the string S has been formed from the DWARF encoding,
2580 an \addtoindex{MD5 hash} is computed for the string and the lower 64 bits
2581 are taken as the type signature.
2583 \textit{The string S is intended to be a flattened representation of
2584 the type that uniquely identifies that type (i.e., a different
2585 type is highly unlikely to produce the same string).}
2587 \textit{A debugging information entry should not be placed in a
2588 separate \addtoindex{type unit}
2589 if any of the following apply:}
2593 \item \textit{The entry has an attribute whose value is a location
2594 expression, and the location expression contains a reference to
2595 another debugging information entry (e.g., a \livelink{chap:DWOPcallref}{DW\-\_OP\-\_call\-\_ref}
2596 operator), as it is unlikely that the entry will remain
2597 identical across compilation units.}
2599 \item \textit{The entry has an attribute whose value refers
2600 to a code location or a \addtoindex{location list}.}
2602 \item \textit{The entry has an attribute whose value refers
2603 to another debugging information entry that does not represent
2608 \textit{Certain attributes are not included in the type signature:}
2611 \item \textit{The \livelink{chap:DWATdeclaration}{DW\-\_AT\-\_declaration} attribute is not included because it
2612 indicates that the debugging information entry represents an
2613 incomplete declaration, and incomplete declarations should
2615 \addtoindexx{type unit}
2616 separate type units.}
2618 \item \textit{The \livelink{chap:DWATdescription}{DW\-\_AT\-\_description} attribute is not included because
2619 it does not provide any information unique to the defining
2620 declaration of the type.}
2622 \item \textit{The \livelink{chap:DWATdeclfile}{DW\-\_AT\-\_decl\-\_file},
2623 \livelink{chap:DWATdeclline}{DW\-\_AT\-\_decl\-\_line}, and
2624 \livelink{chap:DWATdeclcolumn}{DW\-\_AT\-\_decl\-\_column} attributes are not included because they
2625 may vary from one source file to the next, and would prevent
2626 two otherwise identical type declarations from producing the
2627 \addtoindexx{MD5 hash}
2630 \item \textit{The \livelink{chap:DWATobjectpointer}{DW\-\_AT\-\_object\-\_pointer} attribute is not included
2631 because the information it provides is not necessary for the
2632 computation of a unique type signature.}
2636 \textit{Nested types and some types referred to by a debugging
2637 information entry are encoded by name rather than by recursively
2638 encoding the type to allow for cases where a complete definition
2639 of the type might not be available in all compilation units.}
2641 \textit{If a type definition contains the definition of a member function,
2642 it cannot be moved as is into a type unit, because the member function
2643 contains attributes that are unique to that compilation unit.
2644 Such a type definition can be moved to a type unit by rewriting the DIE tree,
2645 moving the member function declaration into a separate declaration tree,
2646 and replacing the function definition in the type with a non-defining
2647 declaration of the function (as if the function had been defined out of
2650 An example that illustrates the computation of an MD5 hash may be found in
2651 Appendix \refersec{app:usingtypeunits}.