1 \chapter{Data Representation}
2 \label{datarep:datarepresentation}
4 This section describes the binary representation of the
5 debugging information entry itself, of the attribute types
6 and of other fundamental elements described above.
9 \section{Vendor Extensibility}
10 \label{datarep:vendorextensibility}
11 \addtoindexx{vendor extensibility}
12 \addtoindexx{vendor specific extensions|see{vendor extensibility}}
15 \addtoindexx{extensibility|see{vendor extensibility}}
16 reserve a portion of the DWARF name space and ranges of
17 enumeration values for use for vendor specific extensions,
18 special labels are reserved for tag names, attribute names,
19 base type encodings, location operations, language names,
20 calling conventions and call frame instructions.
22 The labels denoting the beginning and end of the reserved
23 value range for vendor specific extensions consist of the
24 appropriate prefix (DW\-\_TAG, DW\-\_AT, DW\-\_END, DW\-\_ATE, DW\-\_OP,
25 DW\-\_LANG, DW\-\_LNE, DW\-\_CC or DW\-\_CFA respectively) followed by
26 \_lo\_user or \_hi\_user.
27 \textit{For example, for entry tags, the special
28 labels are \livetarg{chap:DWTAGlouser}{DW\-\_TAG\-\_lo\-\_user} and
29 \livetarg{chap:DWTAGhiuser}{DW\-\_TAG\-\_hi\-\_user}.}
31 range between \textit{prefix}\_lo\_user and \textit{prefix}\_hi\_user inclusive,
32 are reserved for vendor specific extensions. Vendors may
33 use values in this range without conflicting with current or
34 future system\dash defined values. All other values are reserved
35 for use by the system.
37 \textit{There may also be codes for vendor specific extensions
38 between the number of standard line number opcodes and
39 the first special line number opcode. However, since the
40 number of standard opcodes varies with the DWARF version,
41 the range for extensions is also version dependent. Thus,
42 \livetarg{chap:DWLNSlouser}{DW\-\_LNS\-\_lo\-\_user} and
43 \livetarg{chap:DWLNShiuser}{DW\-\_LNS\-\_hi\-\_user} symbols are not defined.
46 Vendor defined tags, attributes, base type encodings, location
47 atoms, language names, line number actions, calling conventions
48 and call frame instructions, conventionally use the form
49 \text{prefix\_vendor\_id\_name}, where
50 \textit{vendor\_id}\addtoindexx{vendor id} is some identifying
51 character sequence chosen so as to avoid conflicts with
54 To ensure that extensions added by one vendor may be safely
55 ignored by consumers that do not understand those extensions,
56 the following rules should be followed:
59 \item New attributes should be added in such a way that a
60 debugger may recognize the format of a new attribute value
61 without knowing the content of that attribute value.
63 \item The semantics of any new attributes should not alter
64 the semantics of previously existing attributes.
66 \item The semantics of any new tags should not conflict with
67 the semantics of previously existing tags.
69 \item Do not add any new forms of attribute value.
74 \section{Reserved Values}
75 \label{datarep:reservedvalues}
76 \subsection{Error Values}
77 \label{datarep:errorvalues}
78 \addtoindexx{reserved values!error}
81 \addtoindexx{error value}
82 a convenience for consumers of DWARF information, the value
83 0 is reserved in the encodings for attribute names, attribute
84 forms, base type encodings, location operations, languages,
85 line number program opcodes, macro information entries and tag
86 names to represent an error condition or unknown value. DWARF
87 does not specify names for these reserved values, since they
88 do not represent valid encodings for the given type and should
89 not appear in DWARF debugging information.
92 \subsection{Initial Length Values}
93 \label{datarep:initiallengthvalues}
94 \addtoindexx{reserved values!initial length}
96 An \addtoindex{initial length field} is one of the length fields that occur
98 of those DWARF sections that
100 (\addtoindex{.debug\_aranges},
101 \addtoindex{.debug\_info},
102 \addtoindex{.debug\_types},
103 \addtoindex{.debug\_line},
104 \addtoindex{.debug\_pubnames}, and
105 \addtoindex{.debug\_pubtypes}) or the length field
106 that occurs at the beginning of the CIE and FDE structures
107 in the \addtoindex{.debug\_frame} section.
109 In an \addtoindex{initial length field}, the values 0xfffffff0 through
110 0xffffffff are reserved by DWARF to indicate some form of
111 extension relative to \addtoindex{DWARF Version 2}; such values must not
112 be interpreted as a length field. The use of one such value,
113 0xffffffff, is defined below
114 (see Section \refersec{datarep:32bitand64bitdwarfformats});
116 the other values is reserved for possible future extensions.
120 \section{Executable Objects and Shared Objects}
121 \label{datarep:executableobjectsandsharedobjects}
123 The relocated addresses in the debugging information for an
124 executable object are virtual addresses and the relocated
125 addresses in the debugging information for a shared object
126 are offsets relative to the start of the lowest region of
127 memory loaded from that shared object.
129 \textit{This requirement makes the debugging information for
130 shared objects position independent. Virtual addresses in a
131 shared object may be calculated by adding the offset to the
132 base address at which the object was attached. This offset
133 is available in the run\dash time linker’s data structures.}
137 \section{32-Bit and 64-Bit DWARF Formats}
138 \label{datarep:32bitand64bitdwarfformats}
140 \addtoindexx{32-bit DWARF format}
141 \addtoindexx{64-bit DWARF format}
142 There are two closely related file formats. In the 32\dash bit DWARF
143 format, all values that represent lengths of DWARF sections
144 and offsets relative to the beginning of DWARF sections are
145 represented using 32\dash bits. In the 64\dash bit DWARF format, all
146 values that represent lengths of DWARF sections and offsets
147 relative to the beginning of DWARF sections are represented
148 using 64\dash bits. A special convention applies to the initial
149 length field of certain DWARF sections, as well as the CIE and
150 FDE structures, so that the 32\dash bit and 64\dash bit DWARF formats
151 can coexist and be distinguished within a single linked object.
153 The differences between the 32\dash\ and 64\dash bit
155 detailed in the following:
158 \begin{enumerate}[1.]
160 \item In the 32\dash bit DWARF format, an
161 \addtoindex{initial length field}
163 \addtoindex{initial length field!encoding}
164 Section \refersec{datarep:initiallengthvalues})
165 is an unsigned 32\dash bit integer (which
166 must be less than 0xfffffff0); in the 64\dash bit DWARF format,
167 an \addtoindex{initial length field} is 96 bits in size,
170 \item The first 32\dash bits have the value 0xffffffff.
172 \item The following 64\dash bits contain the actual length
173 represented as an unsigned 64\dash bit integer.
176 \textit{This representation allows a DWARF consumer to dynamically
177 detect that a DWARF section contribution is using the 64\dash bit
178 format and to adapt its processing accordingly.}
180 \item Section offset and section length
181 \addtoindexx{section length!use in headers}
183 \addtoindexx{section offset!use in headers}
184 in the headers of DWARF sections (other
185 \addtoindex{initial length field}
187 \addtoindex{initial length}
188 fields) are listed following. In the 32\dash bit DWARF format these
189 are 32\dash bit unsigned integer values; in the 64\dash bit DWARF format,
191 \addtoindexx{section length!in .debug\_aranges header}
193 \addtoindexx{section length!in .debug\_pubnames header}
195 \addtoindexx{section length!in .debug\_pubtypes header}
196 unsigned integer values.
200 Section &Name & Role \\ \hline
201 \addtoindex{.debug\_ranges} & \addtoindex{debug\_info\_offset} & offset in \addtoindex{.debug\_info} \\
202 \addtoindex{.debug\_frame}/CIE & \addtoindex{CIE\_id} & CIE distinguished value \\
203 \addtoindex{.debug\_frame}/FDE & \addtoindex{CIE\_pointer} & offset in \addtoindex{.debug\_frame} \\
204 \addtoindex{.debug\_info} & \addtoindex{debug\_abbrev\_offset} & offset in \addtoindex{.debug\_abbrev} \\
205 \addtoindex{.debug\_line} & \addtoindex{header\_length} & length of header itself \\
206 \addtoindex{.debug\_pubnames} & \addtoindex{debug\_info\_offset} & offset in \addtoindex{.debug\_info} \\
207 & \addtoindex{debug\_info\_length} & length of \addtoindex{.debug\_info} \\
209 \addtoindex{.debug\_pubtypes} & \addtoindex{debug\_info\_offset} & offset in \addtoindex{.debug\_info} \\
210 & \addtoindex{debug\_info\_length} & length of \addtoindex{.debug\_info} \\
212 \addtoindex{.debug\_types} & \addtoindex{debug\_abbrev\_offset} & offset in \addtoindex{.debug\_info} \\
213 & \addtoindex{type\_offset} & offset in of \addtoindex{.debug\_types} \\
218 \textit{The CIE\_id field in a CIE structure must be 64 bits because
219 it overlays the CIE\_pointer in a FDE structure; this implicit
220 union must be accessed to distinguish whether a CIE or FDE is
221 present, consequently, these two fields must exactly overlay
222 each other (both offset and size).}
224 \item Within the body of the \addtoindex{.debug\_info} or \addtoindex{.debug\_types}
225 section, certain forms of attribute value depend on the choice
226 of DWARF format as follows. For the 32\dash bit DWARF format,
227 the value is a 32\dash bit unsigned integer; for the 64\dash bit DWARF
228 format, the value is a 64\dash bit unsigned integer.
231 Form & Role \\ \hline
232 \livelink{chap:DWFORMrefaddr}{DW\-\_FORM\-\_ref\-\_addr}& offset in \addtoindex{.debug\_info} \\
233 \livetarg{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}& offset in a section other than \addtoindex{.debug\_info} or \addtoindex{.debug\_str} \\
234 \livelink{chap:DWFORMstrp}{DW\-\_FORM\-\_strp}&offset in \addtoindex{.debug\_str} \\
235 \livelink{chap:DWOPcallref}{DW\-\_OP\-\_call\-\_ref}&offset in \addtoindex{.debug\_info} \\
239 \item Within the body of the \addtoindex{.debug\_pubnames} and
240 \addtoindex{.debug\_pubtypes}
241 sections, the representation of the first field
242 of each tuple (which represents an offset in the
243 \addtoindex{.debug\_info}
244 section) depends on the DWARF format as follows: in the
245 32\dash bit DWARF format, this field is a 32\dash bit unsigned integer;
246 in the 64\dash bit DWARF format, it is a 64\dash bit unsigned integer.
251 The 32\dash bit and 64\dash bit DWARF format conventions must not be
252 intermixed within a single compilation unit.
254 \textit{Attribute values and section header fields that represent
255 addresses in the target program are not affected by these
258 A DWARF consumer that supports the 64\dash bit DWARF format must
259 support executables in which some compilation units use the
260 32\dash bit format and others use the 64\dash bit format provided that
261 the combination links correctly (that is, provided that there
262 are no link\dash time errors due to truncation or overflow). (An
263 implementation is not required to guarantee detection and
264 reporting of all such errors.)
266 \textit{It is expected that DWARF producing compilers will not use
267 the 64\dash bit format by default. In most cases, the division of
268 even very large applications into a number of executable and
269 shared objects will suffice to assure that the DWARF sections
270 within each individual linked object are less than 4 GBytes
271 in size. However, for those cases where needed, the 64\dash bit
272 format allows the unusual case to be handled as well. Even
273 in this case, it is expected that only application supplied
274 objects will need to be compiled using the 64\dash bit format;
275 separate 32\dash bit format versions of system supplied shared
276 executable libraries can still be used.}
280 \section{Format of Debugging Information}
281 \label{datarep:formatofdebugginginformation}
283 For each compilation unit compiled with a DWARF producer,
284 a contribution is made to the \addtoindex{.debug\_info} section of
285 the object file. Each such contribution consists of a
286 compilation unit header
287 (see Section \refersec{datarep:compilationunitheader})
289 single \livelink{chap:DWTAGcompileunit}{DW\-\_TAG\-\_compile\-\_unit} or \livelink{chap:DWTAGpartialunit}{DW\-\_TAG\-\_partial\-\_unit} debugging
290 information entry, together with its children.
292 For each type defined in a compilation unit, a contribution may
293 be made to the \addtoindex{.debug\_types}
294 section of the object file. Each
295 such contribution consists of a type unit header
296 (see Section \refersec{datarep:typeunitheader})
297 followed by a \livelink{chap:DWTAGtypeunit}{DW\-\_TAG\-\_type\-\_unit} entry, together with
300 Each debugging information entry begins with a code that
301 represents an entry in a separate
302 \addtoindex{abbreviations table}. This
303 code is followed directly by a series of attribute values.
305 The appropriate entry in the
306 \addtoindex{abbreviations table} guides the
307 interpretation of the information contained directly in the
308 \addtoindex{.debug\_info} or
309 \addtoindex{.debug\_types} section.
311 Multiple debugging information entries may share the same
312 abbreviation table entry. Each compilation unit is associated
313 with a particular abbreviation table, but multiple compilation
314 units may share the same table.
315 \subsection{Unit Headers}
316 \label{datarep:unitheaders}
318 \subsubsection{Compilation Unit Header}
319 \label{datarep:compilationunitheader}
321 \begin{enumerate}[1.]
323 \item unit\_length (initial length) \\
324 A 4\dash byte or 12\dash byte
325 \addtoindexx{initial length}
326 unsigned integer representing the length
327 of the \addtoindex{.debug\_info}
328 contribution for that compilation unit,
329 not including the length field itself. In the 32\dash bit DWARF
330 format, this is a 4\dash byte unsigned integer (which must be less
331 than 0xfffffff0); in the 64\dash bit DWARF format, this consists
332 of the 4\dash byte value 0xffffffff followed by an 8\dash byte unsigned
333 integer that gives the actual length
334 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
336 \item version (uhalf)
337 A 2\dash byte unsigned integer representing the version of the
338 DWARF information for the compilation unit\addtoindexx{version number!compilation unit}
339 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
340 The value in this field is 4.
342 \item \addtoindex{debug\_abbrev\_offset} (section offset) \\
344 \addtoindexx{section offset!in .debug\_info header}
345 4\dash byte or 8\dash byte unsigned offset into the
346 \addtoindex{.debug\_abbrev}
347 section. This offset associates the compilation unit with a
348 particular set of debugging information entry abbreviations. In
349 the 32\dash bit DWARF format, this is a 4\dash byte unsigned length;
350 in the 64\dash bit DWARF format, this is an 8\dash byte unsigned length
351 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
353 \item address\_size (ubyte) \\
354 A 1\dash byte unsigned integer representing the size in bytes of
355 \addtoindexx{address\_size}
356 an address on the target architecture. If the system uses
357 \addtoindexx{address space!segmented}
358 segmented addressing, this value represents the size of the
359 offset portion of an address.
366 \subsubsection{Type Unit Header}
367 \label{datarep:typeunitheader}
369 The header for the series of debugging information entries
370 contributing to the description of a type that has been
371 placed in its own type unit, within the
372 \addtoindex{.debug\_types} section,
373 consists of the following information:
375 \begin{enumerate}[1.]
377 \item unit\_length (initial 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 (uhalf)
390 A 2\dash byte unsigned integer representing the version of the
391 DWARF information for the compilation unit\addtoindexx{version number!type unit}
392 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
393 The value in this field is 4.
395 \item \addtoindex{debug\_abbrev\_offset} (section offset) \\
397 \addtoindexx{section offset!in .debug\_types header}
398 4\dash byte or 8\dash byte unsigned offset into the
399 \addtoindex{.debug\_abbrev}
400 section. This offset associates the compilation unit with a
401 particular set of debugging information entry abbreviations. In
402 the 32\dash bit DWARF format, this is a 4\dash byte unsigned length;
403 in the 64\dash bit DWARF format, this is an 8\dash byte unsigned length
404 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
406 \item address\_size (ubyte) \\
407 A 1\dash byte unsigned integer representing the size
408 \addtoindexx{size of an address}
410 \addtoindexx{address\_size}
411 an address on the target architecture. If the system uses
412 \addtoindexx{address space!segmented}
413 segmented addressing, this value represents the size of the
414 offset portion of an address.
417 \item type\_signature (8\dash byte unsigned integer) \\
418 A 64\dash bit unique signature of the type described in this type
421 \textit{An attribute that refers(using \livelink{chap:DWFORMrefsig8}{DW\-\_FORM\-\_ref\-\_sig8}) to
422 the primary type contained in this type unit uses this value.}
425 \item type\_offset (section offset) \\
426 A 4\dash byte or 8\dash byte unsigned offset
427 \addtoindexx{section offset!in .debug\_types header}
428 relative to the beginning
429 of the type unit header. This offset refers to the debugging
430 information entry that describes the type. Because the type
431 may be nested inside a namespace or other structures, and may
432 contain references to other types that have not been placed in
433 separate type units, it is not necessarily either the first or
434 the only entry in the type unit. In the 32\dash bit DWARF format,
435 this is a 4\dash byte unsigned length; in the 64\dash bit DWARF format,
436 this is an 8\dash byte unsigned length
437 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
441 \subsection{Debugging Information Entry}
442 \label{datarep:debugginginformationentry}
444 Each debugging information entry begins with an unsigned LEB128
445 number containing the abbreviation code for the entry. This
446 code represents an entry within the abbreviations table
447 associated with the compilation unit containing this entry. The
448 abbreviation code is followed by a series of attribute values.
450 On some architectures, there are alignment constraints on
451 section boundaries. To make it easier to pad debugging
452 information sections to satisfy such constraints, the
453 abbreviation code 0 is reserved. Debugging information entries
454 consisting of only the abbreviation code 0 are considered
457 \subsection{Abbreviations Tables}
458 \label{datarep:abbreviationstables}
460 The abbreviations tables for all compilation units
461 are contained in a separate object file section called
462 \addtoindex{.debug\_abbrev}.
463 As mentioned before, multiple compilation
464 units may share the same abbreviations table.
466 The abbreviations table for a single compilation unit consists
467 of a series of abbreviation declarations. Each declaration
468 specifies the tag and attributes for a particular form of
469 debugging information entry. Each declaration begins with
470 an unsigned LEB128 number representing the abbreviation
471 code itself. It is this code that appears at the beginning
472 of a debugging information entry in the
473 \addtoindex{.debug\_info} or
474 \addtoindex{.debug\_types}
475 section. As described above, the abbreviation
476 code 0 is reserved for null debugging information entries. The
477 abbreviation code is followed by another unsigned LEB128
478 number that encodes the entry’s tag. The encodings for the
479 tag names are given in
480 Table \refersec{tab:tagencodings}.
482 Following the tag encoding is a 1\dash byte value that determines
483 whether a debugging information entry using this abbreviation
484 has child entries or not. If the value is
485 \livetarg{chap:DWCHILDRENyes}{DW\-\_CHILDREN\-\_yes},
486 the next physically succeeding entry of any debugging
487 information entry using this abbreviation is the first
488 child of that entry. If the 1\dash byte value following the
489 abbreviation’s tag encoding is
490 \livetarg{chap:DWCHILDRENno}{DW\-\_CHILDREN\-\_no}, the next
491 physically succeeding entry of any debugging information entry
492 using this abbreviation is a sibling of that entry. (Either
493 the first child or sibling entries may be null entries). The
494 encodings for the child determination byte are given in
495 Table \refersec{tab:childdeterminationencodings}
497 Section \refersec{chap:relationshipofdebugginginformationentries},
499 sibling entries is terminated by a null entry.)
501 Finally, the child encoding is followed by a series of
502 attribute specifications. Each attribute specification
503 consists of two parts. The first part is an unsigned LEB128
504 number representing the attribute’s name. The second part
505 is an unsigned LEB128 number representing the attribute’s
506 form. The series of attribute specifications ends with an
507 entry containing 0 for the name and 0 for the form.
510 \livetarg{chap:DWFORMindirect}{DW\-\_FORM\-\_indirect} is a special case. For
511 attributes with this form, the attribute value itself in the
512 \addtoindex{.debug\_info} or
513 \addtoindex{.debug\_types}
514 section begins with an unsigned
515 LEB128 number that represents its form. This allows producers
516 to choose forms for particular attributes
517 \addtoindexx{abbreviations table!dynamic forms in}
519 without having to add a new entry to the abbreviations table.
521 The abbreviations for a given compilation unit end with an
522 entry consisting of a 0 byte for the abbreviation code.
525 Appendix \refersec{app:compilationunitsandabbreviationstableexample}
526 for a depiction of the organization of the
527 debugging information.
529 \subsection{Attribute Encodings}
530 \label{datarep:attributeencodings}
532 The encodings for the attribute names are given in
533 Table \refersec{tab:attributeencodings}.
535 The attribute form governs how the value of the attribute is
536 encoded. There are nine classes of form, listed below. Each
537 class is a set of forms which have related representations
538 and which are given a common interpretation according to the
539 attribute in which the form is used.
541 Form \livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}
543 \addtoindexx{rangelistptr class}
545 \addtoindexx{macptr class}
547 \addtoindexx{loclistptr class}
549 \addtoindexx{lineptr class}
550 namely \livelink{chap:lineptr}{lineptr},
551 \livelink{chap:loclistptr}{loclistptr},
552 \livelink{chap:macptr}{macptr} or
553 \livelink{chap:rangelistptr}{rangelistptr}; the list
554 of classes allowed by the applicable attribute in
555 Table \refersec{tab:attributeencodings}
556 determines the class of the form.
558 \textit{In DWARF V3 the forms \livelink{chap:DWFORMdata4}{DW\-\_FORM\-\_data4} and \livelink{chap:DWFORMdata8}{DW\-\_FORM\-\_data8} were
559 \addtoindexx{lineptr class}
561 \addtoindexx{rangelistptr class}
563 \addtoindexx{macptr class}
565 \addtoindexx{loclistptr class}
566 class constant \addtoindexx{constant class}
567 or one of the classes
568 \livelink{chap:lineptr}{lineptr},
569 \livelink{chap:loclistptr}{loclistptr},
570 \livelink{chap:macptr}{macptr} or
571 \livelink{chap:rangelistptr}{rangelistptr}, depending on context. In
573 \livelink{chap:DWFORMdata4}{DW\-\_FORM\-\_data4} and
574 \livelink{chap:DWFORMdata8}{DW\-\_FORM\-\_data8} are members of class
575 constant in all cases.
577 \livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset} replaces
578 their usage for the other classes.}
580 Each possible form belongs to one or more of the following classes:
583 \item \livelinki{chap:DWATaddressclass}{address}{address class} \\
584 Represented as an object of appropriate size to hold an
585 address on the target machine
586 (\livetarg{chap:DWFORMaddr}{DW\-\_FORM\-\_addr}).
588 encoded in the compilation unit header
589 (see Section \refersec{datarep:compilationunitheader}).
590 This address is relocatable in a relocatable object file and
591 is relocated in an executable file or shared object.
593 \item \livelink{chap:block}{block} \\
594 Blocks come in four forms:
596 \begin{myindentpara}{1cm}
597 A 1\dash byte length followed by 0 to 255 contiguous information
598 bytes (\livetarg{chap:DWFORMblock1}{DW\-\_FORM\-\_block1}).
601 \begin{myindentpara}{1cm}
602 A 2\dash byte length followed by 0 to 65,535 contiguous information
603 bytes (\livetarg{chap:DWFORMblock2}{DW\-\_FORM\-\_block2}).
607 \begin{myindentpara}{1cm}
608 A 4\dash byte length followed by 0 to 4,294,967,295 contiguous
609 information bytes (\livetarg{chap:DWFORMblock4}{DW\-\_FORM\-\_block4}).
613 \begin{myindentpara}{1cm}
614 An unsigned LEB128 length followed by the number of bytes
615 specified by the length (\livetarg{chap:DWFORMblock}{DW\-\_FORM\-\_block}).
618 In all forms, the length is the number of information bytes
619 that follow. The information bytes may contain any mixture
620 of relocated (or relocatable) addresses, references to other
621 debugging information entries or data bytes.
624 There are six forms of constants. There are fixed length
625 constant data forms for one, two, four and eight byte values
627 \livetarg{chap:DWFORMdata1}{DW\-\_FORM\-\_data1},
628 \livetarg{chap:DWFORMdata2}{DW\-\_FORM\-\_data2},
629 \livetarg{chap:DWFORMdata4}{DW\-\_FORM\-\_data4},
630 and \livetarg{chap:DWFORMdata8}{DW\-\_FORM\-\_data8}).
631 There are also variable length constant
632 data forms encoded using LEB128 numbers (see below). Both
633 signed (\livetarg{chap:DWFORMsdata}{DW\-\_FORM\-\_sdata}) and unsigned
634 (\livetarg{chap:DWFORMudata}{DW\-\_FORM\-\_udata}) variable
635 length constants are available
637 The data in \livelink{chap:DWFORMdata1}{DW\-\_FORM\-\_data1},
638 \livelink{chap:DWFORMdata2}{DW\-\_FORM\-\_data2},
639 \livelink{chap:DWFORMdata4}{DW\-\_FORM\-\_data4} and
640 \livelink{chap:DWFORMdata8}{DW\-\_FORM\-\_data8}
641 can be anything. Depending on context, it may
642 be a signed integer, an unsigned integer, a floating\dash point
643 constant, or anything else. A consumer must use context to
644 know how to interpret the bits, which if they are target
645 machine data (such as an integer or floating point constant)
646 will be in target machine byte\dash order.
648 \textit{If one of the \livetarg{chap:DWFORMdata}{DW\-\_FORM\-\_data}<n> forms is used to represent a
649 signed or unsigned integer, it can be hard for a consumer
650 to discover the context necessary to determine which
651 interpretation is intended. Producers are therefore strongly
652 encouraged to use \livelink{chap:DWFORMsdata}{DW\-\_FORM\-\_sdata} or
653 \livelink{chap:DWFORMudata}{DW\-\_FORM\-\_udata} for signed and
654 unsigned integers respectively, rather than
655 \livelink{chap:DWFORMdata}{DW\-\_FORM\-\_data} \textless n \textgreater.}
658 \item \livelink{chap:exprloc}{exprloc} \\
659 This is an unsigned LEB128 length followed by the
660 number of information bytes specified by the length
661 (\livetarg{chap:DWFORMexprloc}{DW\-\_FORM\-\_exprloc}).
662 The information bytes contain a DWARF
664 (see Section \refersec{chap:dwarfexpressions})
665 or location description
666 (see Section \refersec{chap:locationdescriptions}).
668 \item \livelink{chap:flag}{flag} \\
669 A flag \addtoindexx{flag class}
670 is represented explicitly as a single byte of data
671 (\livetarg{chap:DWFORMflag}{DW\-\_FORM\-\_flag}) or
672 implicitly (\livetarg{chap:DWFORMflagpresent}{DW\-\_FORM\-\_flag\-\_present}).
674 first case, if the \nolink{flag} has value zero, it indicates the
675 absence of the attribute; if the \nolink{flag} has a non\dash zero value,
676 it indicates the presence of the attribute. In the second
677 case, the attribute is implicitly indicated as present, and
678 no value is encoded in the debugging information entry itself.
680 \item \livelink{chap:lineptr}{lineptr} \\
681 This is an offset into
682 \addtoindexx{section offset!in class lineptr value}
684 \addtoindex{.debug\_line} section
685 (\livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}).
686 It consists of an offset from the
688 \addtoindex{.debug\_line}
689 section to the first byte of
690 the data making up the line number list for the compilation
692 It is relocatable in a relocatable object file, and
693 relocated in an executable or shared object. In the 32\dash bit
694 DWARF format, this offset is a 4\dash byte unsigned value;
695 in the 64\dash bit DWARF format, it is an 8\dash byte unsigned value
696 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
699 \item \livelink{chap:loclistptr}{loclistptr} \\
700 This is an offset into the
701 \addtoindex{.debug\_loc}
703 (\livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}).
704 It consists of an offset from the
705 \addtoindexx{section offset!in class loclistptr value}
707 \addtoindex{.debug\_loc}
708 section to the first byte of
709 the data making up the
710 \addtoindex{location list} for the compilation
712 It is relocatable in a relocatable object file, and
713 relocated in an executable or shared object. In the 32\dash bit
714 DWARF format, this offset is a 4\dash byte unsigned value;
715 in the 64\dash bit DWARF format, it is an 8\dash byte unsigned value
716 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
719 \item \livelink{chap:macptr}{macptr} \\
721 \addtoindexx{section offset!in class macptr value}
723 \addtoindex{.debug\_macinfo} section
724 (\livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}). It consists of an offset from the
725 beginning of the \addtoindex{.debug\_macinfo}
726 section to the first byte of
727 the data making up the macro information list for the compilation
729 It is relocatable in a relocatable object file, and
730 relocated in an executable or shared object. In the 32\dash bit
731 DWARF format, this offset is a 4\dash byte unsigned value;
732 in the 64\dash bit DWARF format, it is an 8\dash byte unsigned value
733 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
735 \item \livelink{chap:rangelistptr}{rangelistptr} \\
737 \addtoindexx{section offset!in class rangelistptr value}
738 offset into the \addtoindex{.debug\_ranges} section
739 (\livelink{chap:DWFORMsecoffset}{DW\-\_FORM\-\_sec\-\_offset}).
741 offset from the beginning of the
742 \addtoindex{.debug\_ranges} section
743 to the beginning of the non\dash contiguous address ranges
744 information for the referencing entity.
746 a relocatable object file, and relocated in an executable or
747 shared object. In the 32\dash bit DWARF format, this offset
748 is a 4\dash byte unsigned value; in the 64\dash bit DWARF
749 format, it is an 8\dash byte unsigned value (see Section
750 \refersec{datarep:32bitand64bitdwarfformats}).
753 \textit{Because classes \livelink{chap:lineptr}{lineptr}, \livelink{chap:loclistptr}{loclistptr}, \livelink{chap:macptr}{macptr} and \livelink{chap:rangelistptr}{rangelistptr}
754 share a common representation, it is not possible for an
755 attribute to allow more than one of these classes}
760 There are three types of reference.
763 \addtoindexx{reference class}
764 first type of reference can identify any debugging
765 information entry within the containing unit.
768 \addtoindexx{section offset!in class reference value}
769 offset from the first byte of the compilation
770 header for the compilation unit containing the reference. There
771 are five forms for this type of reference. There are fixed
772 length forms for one, two, four and eight byte offsets
773 (respectively, \livetarg{chap:DWFORMref1}{DW\-\_FORM\-\_ref1},
774 \livetarg{chap:DWFORMref2}{DW\-\_FORM\-\_ref2},
775 \livetarg{chap:DWFORMref4}{DW\-\_FORM\-\_ref4},
776 and \livetarg{chap:DWFORMref8}{DW\-\_FORM\-\_ref8}).
777 There is also an unsigned variable
778 length offset encoded form that uses unsigned LEB128 numbers
779 (\livetarg{chap:DWFORMrefudata}{DW\-\_FORM\-\_ref\-\_udata}).
780 Because this type of reference is within
781 the containing compilation unit no relocation of the value
784 The second type of reference can identify any debugging
785 information entry within a
786 \addtoindex{.debug\_info} section; in particular,
787 it may refer to an entry in a different compilation unit
788 from the unit containing the reference, and may refer to an
789 entry in a different shared object. This type of reference
790 (\livetarg{chap:DWFORMrefaddr}{DW\-\_FORM\-\_ref\-\_addr}) is an offset from the beginning of the
791 \addtoindex{.debug\_info}
792 section of the target executable or shared object;
793 it is relocatable in a relocatable object file and frequently
794 relocated in an executable file or shared object. For
795 references from one shared object or static executable file
796 to another, the relocation and identification of the target
797 object must be performed by the consumer. In the 32\dash bit DWARF
798 format, this offset is a 4\dash byte unsigned value;
799 in the 64\dash bit DWARF format, it is an 8\dash byte
801 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
803 A debugging information entry that may be referenced by
804 another compilation unit using \livelink{chap:DWFORMrefaddr}{DW\-\_FORM\-\_ref\-\_addr} must have a
805 global symbolic name.
807 For a reference from one executable or shared object to
808 another, the reference is resolved by the debugger to identify
809 the shared object or executable and the offset into that
810 object’s \addtoindex{.debug\_info}
811 section in the same fashion as the run
812 time loader, either when the debug information is first read,
813 or when the reference is used.
815 The third type of reference can identify any debugging
816 information type entry that has been placed in its own
817 type unit. This type of
818 reference (\livetarg{chap:DWFORMrefsig8}{DW\-\_FORM\-\_ref\-\_sig8}) is the
819 64\dash bit type signature
820 (see Section \refersec{datarep:typesignaturecomputation})
824 The use of compilation unit relative references will reduce the
825 number of link\dash time relocations and so speed up linking. The
826 use of the second and third type of reference allows for the
827 sharing of information, such as types, across compilation
830 A reference to any kind of compilation unit identifies the
831 debugging information entry for that unit, not the preceding
835 A string is a sequence of contiguous non\dash null bytes followed by
837 \addtoindexx{string class}
838 A string may be represented immediately in the
839 debugging information entry itself
840 (\livetarg{chap:DWFORMstring}{DW\-\_FORM\-\_string}), or may
842 \addtoindexx{section offset!in class string value}
843 offset into a string table contained in
844 the \addtoindex{.debug\_str} section of the object file
845 (\livetarg{chap:DWFORMstrp}{DW\-\_FORM\-\_strp}). In
846 the 32\dash bit DWARF format, the representation of a
847 \livelink{chap:DWFORMstrp}{DW\-\_FORM\-\_strp}
848 value is a 4\dash byte unsigned offset; in the 64\dash bit DWARF format,
849 it is an 8\dash byte unsigned offset
850 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
852 If the \livelink{chap:DWATuseUTF8}{DW\-\_AT\-\_use\-\_UTF8} attribute is specified for the
853 compilation unit entry, string values are encoded using the
854 UTF\dash 8 (Unicode Transformation Format\dash 8) from the Universal
855 Character Set standard (ISO/IEC 10646\dash 1:1993). Otherwise,
856 the string representation is unspecified.
858 The Unicode Standard Version 3 is fully compatible with
859 ISO/IEC 10646\dash 1:1993. It contains all the same characters
860 and encoding points as ISO/IEC 10646, as well as additional
861 information about the characters and their use.
863 Earlier versions of DWARF did not specify the representation
864 of strings; for compatibility, this version also does
865 not. However, the UTF\dash 8 representation is strongly recommended.
869 In no case does an attribute use
870 \addtoindexx{rangelistptr class}
872 \addtoindexx{loclistptr class}
874 \addtoindexx{lineptr class}
876 \addtoindexx{macptr class}
877 classes \livelink{chap:lineptr}{lineptr},
878 \livelink{chap:loclistptr}{loclistptr}, \livelink{chap:macptr}{macptr} or \livelink{chap:rangelistptr}{rangelistptr} to point into either the
879 \addtoindex{.debug\_info} or \addtoindex{.debug\_str} section.
881 The form encodings are listed in
882 Table \refersec{tab:attributeformencodings}.
885 \setlength{\extrarowheight}{0.1cm}
886 \begin{longtable}{l|l}
887 \caption{Tag encodings} \label{tab:tagencodings} \\
888 \hline \\ \bfseries Tag name&\bfseries Value\\ \hline
890 \bfseries Tag name&\bfseries Value \\ \hline
892 \hline \emph{Continued on next page}
896 \livelink{chap:DWTAGarraytype}{DW\-\_TAG\-\_array\-\_type} &0x01 \\
897 \livelink{chap:DWTAGclasstype}{DW\-\_TAG\-\_class\-\_type}&0x02 \\
898 \livelink{chap:DWTAGentrypoint}{DW\-\_TAG\-\_entry\-\_point}&0x03 \\
899 \livelink{chap:DWTAGenumerationtype}{DW\-\_TAG\-\_enumeration\-\_type}&0x04 \\
900 \livelink{chap:DWTAGformalparameter}{DW\-\_TAG\-\_formal\-\_parameter}&0x05 \\
901 \livelink{chap:DWTAGimporteddeclaration}{DW\-\_TAG\-\_imported\-\_declaration}&0x08 \\
902 \livelink{chap:DWTAGlabel}{DW\-\_TAG\-\_label}&0x0a \\
903 \livelink{chap:DWTAGlexicalblock}{DW\-\_TAG\-\_lexical\-\_block}&0x0b \\
904 \livelink{chap:DWTAGmember}{DW\-\_TAG\-\_member}&0x0d \\
905 \livelink{chap:DWTAGpointertype}{DW\-\_TAG\-\_pointer\-\_type}&0x0f \\
906 \livelink{chap:DWTAGreferencetype}{DW\-\_TAG\-\_reference\-\_type}&0x10 \\
907 \livelink{chap:DWTAGcompileunit}{DW\-\_TAG\-\_compile\-\_unit}&0x11 \\
908 \livelink{chap:DWTAGstringtype}{DW\-\_TAG\-\_string\-\_type}&0x12 \\
909 \livelink{chap:DWTAGstructuretype}{DW\-\_TAG\-\_structure\-\_type}&0x13 \\
910 \livelink{chap:DWTAGsubroutinetype}{DW\-\_TAG\-\_subroutine\-\_type}&0x15 \\
911 \livelink{chap:DWTAGtypedef}{DW\-\_TAG\-\_typedef}&0x16 \\
912 \livelink{chap:DWTAGuniontype}{DW\-\_TAG\-\_union\-\_type}&0x17 \\
913 \livelink{chap:DWTAGunspecifiedparameters}{DW\-\_TAG\-\_unspecified\-\_parameters}&0x18 \\
914 \livelink{chap:DWTAGvariant}{DW\-\_TAG\-\_variant}&0x19 \\
915 \livelink{chap:DWTAGcommonblock}{DW\-\_TAG\-\_common\-\_block}&0x1a \\
916 \livelink{chap:DWTAGcommoninclusion}{DW\-\_TAG\-\_common\-\_inclusion}&0x1b \\
917 \livelink{chap:DWTAGinheritance}{DW\-\_TAG\-\_inheritance}&0x1c \\
918 \livelink{chap:DWTAGinlinedsubroutine}{DW\-\_TAG\-\_inlined\-\_subroutine}&0x1d \\
919 \livelink{chap:DWTAGmodule}{DW\-\_TAG\-\_module}&0x1e \\
920 \livelink{chap:DWTAGptrtomembertype}{DW\-\_TAG\-\_ptr\-\_to\-\_member\-\_type}&0x1f \\
921 \livelink{chap:DWTAGsettype}{DW\-\_TAG\-\_set\-\_type}&0x20 \\
922 \livelink{chap:DWTAGsubrangetype}{DW\-\_TAG\-\_subrange\-\_type}&0x21 \\
923 \livelink{chap:DWTAGwithstmt}{DW\-\_TAG\-\_with\-\_stmt}&0x22 \\
924 \livelink{chap:DWTAGaccessdeclaration}{DW\-\_TAG\-\_access\-\_declaration}&0x23 \\
925 \livelink{chap:DWTAGbasetype}{DW\-\_TAG\-\_base\-\_type}&0x24 \\
926 \livelink{chap:DWTAGcatchblock}{DW\-\_TAG\-\_catch\-\_block}&0x25 \\
927 \livelink{chap:DWTAGconsttype}{DW\-\_TAG\-\_const\-\_type}&0x26 \\
928 \livelink{chap:DWTAGconstant}{DW\-\_TAG\-\_constant}&0x27 \\
929 \livelink{chap:DWTAGenumerator}{DW\-\_TAG\-\_enumerator}&0x28 \\
930 \livelink{chap:DWTAGfiletype}{DW\-\_TAG\-\_file\-\_type}&0x29 \\
931 \livelink{chap:DWTAGfriend}{DW\-\_TAG\-\_friend}&0x2a \\
932 \livelink{chap:DWTAGnamelist}{DW\-\_TAG\-\_namelist}&0x2b \\
933 \livelink{chap:DWTAGnamelistitem}{DW\-\_TAG\-\_namelist\-\_item}&0x2c \\
934 \livelink{chap:DWTAGpackedtype}{DW\-\_TAG\-\_packed\-\_type}&0x2d \\
935 \livelink{chap:DWTAGsubprogram}{DW\-\_TAG\-\_subprogram}&0x2e \\
936 \livelink{chap:DWTAGtemplatetypeparameter}{DW\-\_TAG\-\_template\-\_type\-\_parameter}&0x2f \\
937 \livelink{chap:DWTAGtemplatevalueparameter}{DW\-\_TAG\-\_template\-\_value\-\_parameter}&0x30 \\
938 \livelink{chap:DWTAGthrowntype}{DW\-\_TAG\-\_thrown\-\_type}&0x31 \\
939 \livelink{chap:DWTAGtryblock}{DW\-\_TAG\-\_try\-\_block}&0x32 \\
940 \livelink{chap:DWTAGvariantpart}{DW\-\_TAG\-\_variant\-\_part}&0x33 \\
941 \livelink{chap:DWTAGvariable}{DW\-\_TAG\-\_variable}&0x34 \\
942 \livelink{chap:DWTAGvolatiletype}{DW\-\_TAG\-\_volatile\-\_type}&0x35 \\
943 \livelink{chap:DWTAGdwarfprocedure}{DW\-\_TAG\-\_dwarf\-\_procedure}&0x36 \\
944 \livelink{chap:DWTAGrestricttype}{DW\-\_TAG\-\_restrict\-\_type}&0x37 \\
945 \livelink{chap:DWTAGinterfacetype}{DW\-\_TAG\-\_interface\-\_type}&0x38 \\
946 \livelink{chap:DWTAGnamespace}{DW\-\_TAG\-\_namespace}&0x39 \\
947 \livelink{chap:DWTAGimportedmodule}{DW\-\_TAG\-\_imported\-\_module}&0x3a \\
948 \livelink{chap:DWTAGunspecifiedtype}{DW\-\_TAG\-\_unspecified\-\_type}&0x3b \\
949 \livelink{chap:DWTAGpartialunit}{DW\-\_TAG\-\_partial\-\_unit}&0x3c \\
950 \livelink{chap:DWTAGimportedunit}{DW\-\_TAG\-\_imported\-\_unit}&0x3d \\
951 \livelink{chap:DWTAGcondition}{DW\-\_TAG\-\_condition}&0x3f \\
952 \livelink{chap:DWTAGsharedtype}{DW\-\_TAG\-\_shared\-\_type}&0x40 \\
953 \livelink{chap:DWTAGtypeunit}{DW\-\_TAG\-\_type\-\_unit} \ddag &0x41 \\
954 \livelink{chap:DWTAGrvaluereferencetype}{DW\-\_TAG\-\_rvalue\-\_reference\-\_type} \ddag &0x42 \\
955 \livelink{chap:DWTAGtemplatealias}{DW\-\_TAG\-\_template\-\_alias} \ddag &0x43 \\
956 \livelink{chap:DWTAGlouser}{DW\-\_TAG\-\_lo\-\_user}&0x4080 \\
957 \livelink{chap:DWTAGhiuser}{DW\-\_TAG\-\_hi\-\_user}&0xffff \\
959 \ddag TAG new in \addtoindex{DWARF Version 4}
965 \setlength{\extrarowheight}{0.1cm}
966 \caption{Child determination encodings}
967 \label{tab:childdeterminationencodings}
968 \begin{tabular}{l|l} \hline
969 Child determination name& Value\\ \hline
970 \livelink{chap:DWCHILDRENno}{DW\-\_CHILDREN\-\_no}&0x00 \\
971 \livelink{chap:DWCHILDRENyes}{DW\-\_CHILDREN\-\_yes}&0x01 \\ \hline
977 \setlength{\extrarowheight}{0.1cm}
978 \begin{longtable}{l|l|l}
979 \caption{Attribute encodings} \label{tab:attributeencodings} \addtoindexx{attribute encodings} \\
980 \hline \\ \bfseries Attribute name&\bfseries Value &\bfseries Classes \\ \hline
982 \bfseries Attribute name&\bfseries Value &\bfseries Classes\\ \hline
984 \hline \emph{Continued on next page}
988 \livelink{chap:DWATsibling}{DW\-\_AT\-\_sibling}&0x01&reference
989 \addtoindexx{sibling attribute!encoding} \\
990 \livelink{chap:DWATlocation}{DW\-\_AT\-\_location}&0x02&\livelink{chap:exprloc}{exprloc},
991 \livelink{chap:loclistptr}{loclistptr}\addtoindex{location attribute!encoding} \\
992 \livelink{chap:DWATname}{DW\-\_AT\-\_name}&0x03&string
993 \addtoindexx{name attribute!encoding} \\
994 \livelink{chap:DWATordering}{DW\-\_AT\-\_ordering}&0x09&constant
995 \addtoindexx{ordering attribute!encoding} \\
996 \livelink{chap:DWATbytesize}{DW\-\_AT\-\_byte\-\_size}&0x0b&constant, \livelink{chap:exprloc}{exprloc},
997 reference \addtoindexx{byte size attribute!encoding} \\
998 \livelink{chap:DWATbitoffset}{DW\-\_AT\-\_bit\-\_offset}&0x0c&constant,
999 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{bit offset attribute!encoding} \\
1000 \livelink{chap:DWATbitsize}{DW\-\_AT\-\_bit\-\_size}&0x0d&constant,
1001 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{bit size attribute!encoding} \\
1002 \livelink{chap:DWATstmtlist}{DW\-\_AT\-\_stmt\-\_list}&0x10&\livelink{chap:lineptr}{lineptr}
1003 \addtoindex{statement list attribute!encoding} \\
1004 \livelink{chap:DWATlowpc}{DW\-\_AT\-\_low\-\_pc}&0x11&address
1005 \addtoindexx{low PC attribute!encoding} \\
1006 \livelink{chap:DWAThighpc}{DW\-\_AT\-\_high\-\_pc}&0x12&address, constant
1007 \addtoindexx{high PC attribute!encoding} \\
1008 \livelink{chap:DWATlanguage}{DW\-\_AT\-\_language}&0x13&constant
1009 \addtoindexx{language attribute!encoding} \\
1010 \livelink{chap:DWATdiscr}{DW\-\_AT\-\_discr}&0x15&reference
1011 \addtoindexx{discriminant attribute!encoding} \\
1012 \livelink{chap:DWATdiscrvalue}{DW\-\_AT\-\_discr\-\_value}&0x16&constant
1013 \addtoindexx{discriminant value attribute!encoding} \\
1014 \livelink{chap:DWATvisibility}{DW\-\_AT\-\_visibility}&0x17&constant
1015 \addtoindexx{visibility attribute!encoding} \\
1016 \livelink{chap:DWATimport}{DW\-\_AT\-\_import}&0x18&reference
1017 \addtoindexx{import attribute!encoding} \\
1018 \livelink{chap:DWATstringlength}{DW\-\_AT\-\_string\-\_length}&0x19&\livelink{chap:exprloc}{exprloc},
1019 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{string length attribute!encoding} \\
1020 \livelink{chap:DWATcommonreference}{DW\-\_AT\-\_common\-\_reference}&0x1a&reference
1021 \addtoindexx{common reference attribute!encoding} \\
1022 \livelink{chap:DWATcompdir}{DW\-\_AT\-\_comp\-\_dir}&0x1b&string
1023 \addtoindexx{compilation directory attribute!encoding} \\
1024 \livelink{chap:DWATconstvalue}{DW\-\_AT\-\_const\-\_value}&0x1c&\livelink{chap:block}{block}, constant, string
1025 \addtoindexx{constant value attribute!encoding} \\
1026 \livelink{chap:DWATcontainingtype}{DW\-\_AT\-\_containing\-\_type}&0x1d&reference
1027 \addtoindexx{containing type attribute!encoding} \\
1028 \livelink{chap:DWATdefaultvalue}{DW\-\_AT\-\_default\-\_value}&0x1e&reference
1029 \addtoindexx{default value attribute!encoding} \\
1030 \livelink{chap:DWATinline}{DW\-\_AT\-\_inline}&0x20&constant
1031 \addtoindexx{inline attribute!encoding} \\
1032 \livelink{chap:DWATisoptional}{DW\-\_AT\-\_is\-\_optional}&0x21&\livelink{chap:flag}{flag}
1033 \addtoindexx{is optional attribute!encoding} \\
1034 \livelink{chap:DWATlowerbound}{DW\-\_AT\-\_lower\-\_bound}&0x22&constant,
1035 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{lower bound attribute!encoding} \\
1036 \livelink{chap:DWATproducer}{DW\-\_AT\-\_producer}&0x25&string \addtoindexx{producer attribute!encoding} \\
1037 \livelink{chap:DWATprototyped}{DW\-\_AT\-\_prototyped}&0x27&\livelink{chap:flag}{flag}
1038 \addtoindexx{prototyped attribute!encoding} \\
1039 \livelink{chap:DWATreturnaddr}{DW\-\_AT\-\_return\-\_addr}&0x2a&\livelink{chap:exprloc}{exprloc},
1040 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{return address attribute!encoding} \\
1041 % FIXME: lower case , not Constant
1042 \livelink{chap:DWATstartscope}{DW\-\_AT\-\_start\-\_scope}&0x2c&Constant,
1043 \livelink{chap:rangelistptr}{rangelistptr} \addtoindexx{start scope attribute!encoding} \\
1044 \livelink{chap:DWATbitstride}{DW\-\_AT\-\_bit\-\_stride}&0x2e&constant,
1045 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{bit stride attribute!encoding} \\
1046 \livelink{chap:DWATupperbound}{DW\-\_AT\-\_upper\-\_bound}&0x2f&constant,
1047 \livelink{chap:exprloc}{exprloc}, reference \addtoindexx{upper bound attribute!encoding} \\
1048 \livelink{chap:DWATabstractorigin}{DW\-\_AT\-\_abstract\-\_origin}&0x31&reference
1049 \addtoindexx{abstract origin attribute!encoding} \\
1050 \livelink{chap:DWATaccessibility}{DW\-\_AT\-\_accessibility}&0x32&constant
1051 \addtoindexx{accessibility attribute!encoding} \\
1052 \livelink{chap:DWATaddressclass}{DW\-\_AT\-\_address\-\_class}&0x33&constant
1053 \addtoindexx{address class atribute!encoding} \\
1054 \livelink{chap:DWATartificial}{DW\-\_AT\-\_artificial}&0x34&\livelink{chap:flag}{flag}
1055 \addtoindexx{artificial attribute!encoding} \\
1056 \livelink{chap:DWATbasetypes}{DW\-\_AT\-\_base\-\_types}&0x35&reference
1057 \addtoindexx{base types attribute!encoding} \\
1058 \livelink{chap:DWATcallingconvention}{DW\-\_AT\-\_calling\-\_convention}&0x36&constant
1059 \addtoindexx{calling convention attribute!encoding} \\
1060 \livelink{chap:DWATcount}{DW\-\_AT\-\_count}&0x37&constant, \livelink{chap:exprloc}{exprloc}, reference
1061 \addtoindexx{count attribute!encoding} \\
1062 \livelink{chap:DWATdatamemberlocation}{DW\-\_AT\-\_data\-\_member\-\_location}&0x38&constant,
1063 \livelink{chap:exprloc}{exprloc}, \livelink{chap:loclistptr}{loclistptr}
1064 \addtoindexx{data member attribute!encoding} \\
1065 \livelink{chap:DWATdeclcolumn}{DW\-\_AT\-\_decl\-\_column}&0x39&constant
1066 \addtoindexx{declaration column attribute!encoding} \\
1067 \livelink{chap:DWATdeclfile}{DW\-\_AT\-\_decl\-\_file}&0x3a&constant
1068 \addtoindexx{declaration file attribute!encoding} \\
1069 \livelink{chap:DWATdeclline}{DW\-\_AT\-\_decl\-\_line}&0x3b&constant
1070 \addtoindexx{declaration line attribute!encoding} \\
1071 \livelink{chap:DWATdeclaration}{DW\-\_AT\-\_declaration}&0x3c&\livelink{chap:flag}{flag}
1072 \addtoindexx{declaration attribute!encoding} \\
1073 \livelink{chap:DWATdiscrlist}{DW\-\_AT\-\_discr\-\_list}&0x3d&\livelink{chap:block}{block}
1074 \addtoindexx{discriminant list attribute!encoding} \\
1075 \livelink{chap:DWATencoding}{DW\-\_AT\-\_encoding}&0x3e&constant
1076 \addtoindexx{encoding attribute!encoding} \\
1077 \livelink{chap:DWATexternal}{DW\-\_AT\-\_external}&0x3f&\livelink{chap:flag}{flag}
1078 \addtoindexx{external attribute!encoding} \\
1079 \livelink{chap:DWATframebase}{DW\-\_AT\-\_frame\-\_base}&0x40&\livelink{chap:exprloc}{exprloc},
1080 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{frame base attribute!encoding} \\
1081 \livelink{chap:DWATfriend}{DW\-\_AT\-\_friend}&0x41&reference
1082 \addtoindexx{friend attribute!encoding} \\
1083 \livelink{chap:DWATidentifiercase}{DW\-\_AT\-\_identifier\-\_case}&0x42&constant
1084 \addtoindexx{identifier case attribute!encoding} \\
1085 \livelink{chap:DWATmacroinfo}{DW\-\_AT\-\_macro\-\_info}&0x43&\livelink{chap:macptr}{macptr}
1086 \addtoindexx{macro information attribute!encoding} \\
1087 \livelink{chap:DWATnamelistitem}{DW\-\_AT\-\_namelist\-\_item}&0x44&reference
1088 \addtoindexx{name list item attribute!encoding} \\
1089 \livelink{chap:DWATpriority}{DW\-\_AT\-\_priority}&0x45&reference
1090 \addtoindexx{priority attribute!encoding} \\
1091 \livelink{chap:DWATsegment}{DW\-\_AT\-\_segment}&0x46&\livelink{chap:exprloc}{exprloc},
1092 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{segment attribute!encoding} \\
1093 \livelink{chap:DWATspecification}{DW\-\_AT\-\_specification}&0x47&reference
1094 \addtoindexx{specification attribute!encoding} \\
1095 \livelink{chap:DWATstaticlink}{DW\-\_AT\-\_static\-\_link}&0x48&\livelink{chap:exprloc}{exprloc},
1096 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{static link attribute!encoding} \\
1097 \livelink{chap:DWATtype}{DW\-\_AT\-\_type}&0x49&reference
1098 \addtoindexx{type attribute!encoding} \\
1099 \livelink{chap:DWATuselocation}{DW\-\_AT\-\_use\-\_location}&0x4a&\livelink{chap:exprloc}{exprloc},
1100 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{location list attribute!encoding} \\
1101 \livelink{chap:DWATvariableparameter}{DW\-\_AT\-\_variable\-\_parameter}&0x4b&\livelink{chap:flag}{flag}
1102 \addtoindexx{variable parameter attribute!encoding} \\
1103 \livelink{chap:DWATvirtuality}{DW\-\_AT\-\_virtuality}&0x4c&constant
1104 \addtoindexx{virtuality attribute!encoding} \\
1105 \livelink{chap:DWATvtableelemlocation}{DW\-\_AT\-\_vtable\-\_elem\-\_location}&0x4d&\livelink{chap:exprloc}{exprloc},
1106 \livelink{chap:loclistptr}{loclistptr} \addtoindexx{vtable element location attribute!encoding} \\
1108 \livelink{chap:DWATallocated}{DW\-\_AT\-\_allocated}&0x4e&constant, \livelink{chap:exprloc}{exprloc},
1109 reference \addtoindexx{allocated attribute!encoding} \\
1110 \livelink{chap:DWATassociated}{DW\-\_AT\-\_associated}&0x4f&constant, \livelink{chap:exprloc}{exprloc},
1111 reference \addtoindexx{associated attribute!encoding} \\
1112 \livelink{chap:DWATdatalocation}{DW\-\_AT\-\_data\-\_location}&0x50&\livelink{chap:exprloc}{exprloc}
1113 \addtoindexx{data location attribute!encoding} \\
1114 \livelink{chap:DWATbytestride}{DW\-\_AT\-\_byte\-\_stride}&0x51&constant, \livelink{chap:exprloc}{exprloc},
1115 reference \addtoindexx{byte stride attribute!encoding} \\
1116 \livelink{chap:DWATentrypc}{DW\-\_AT\-\_entry\-\_pc}&0x52&address
1117 \addtoindexx{entry pc attribute!encoding} \\
1118 \livelink{chap:DWATuseUTF8}{DW\-\_AT\-\_use\-\_UTF8}&0x53&\livelink{chap:flag}{flag}
1119 \addtoindexx{use UTF8 attribute!encoding} \\
1120 \livelink{chap:DWATextension}{DW\-\_AT\-\_extension}&0x54&reference
1121 \addtoindexx{extension attribute!encoding} \\
1122 \livelink{chap:DWATranges}{DW\-\_AT\-\_ranges}&0x55&\livelink{chap:rangelistptr}{rangelistptr}
1123 \addtoindexx{ranges attribute!encoding} \\
1124 \livelink{chap:DWATtrampoline}{DW\-\_AT\-\_trampoline}&0x56&address, \livelink{chap:flag}{flag},
1125 reference, string \addtoindexx{trampoline attribute!encoding} \\
1126 \livelink{chap:DWATcallcolumn}{DW\-\_AT\-\_call\-\_column}&0x57&constant
1127 \addtoindexx{call column attribute!encoding} \\
1128 \livelink{chap:DWATcallfile}{DW\-\_AT\-\_call\-\_file}&0x58&constant
1129 \addtoindexx{call file attribute!encoding} \\
1130 \livelink{chap:DWATcallline}{DW\-\_AT\-\_call\-\_line}&0x59&constant
1131 \addtoindexx{call line attribute!encoding} \\
1132 \livelink{chap:DWATdescription}{DW\-\_AT\-\_description}&0x5a&string
1133 \addtoindexx{description attribute!encoding} \\
1134 \livelink{chap:DWATbinaryscale}{DW\-\_AT\-\_binary\-\_scale}&0x5b&constant
1135 \addtoindexx{binary scale attribute!encoding} \\
1136 \livelink{chap:DWATdecimalscale}{DW\-\_AT\-\_decimal\-\_scale}&0x5c&constant
1137 \addtoindexx{decimal scale attribute!encoding} \\
1138 \livelink{chap:DWATsmall}{DW\-\_AT\-\_small} &0x5d&reference
1139 \addtoindexx{small attribute!encoding} \\
1140 \livelink{chap:DWATdecimalsign}{DW\-\_AT\-\_decimal\-\_sign}&0x5e&constant
1141 \addtoindexx{decimal scale attribute!encoding} \\
1142 \livelink{chap:DWATdigitcount}{DW\-\_AT\-\_digit\-\_count}&0x5f&constant
1143 \addtoindexx{digit count attribute!encoding} \\
1144 \livelink{chap:DWATpicturestring}{DW\-\_AT\-\_picture\-\_string}&0x60&string
1145 \addtoindexx{picture string attribute!encoding} \\
1146 \livelink{chap:DWATmutable}{DW\-\_AT\-\_mutable}&0x61&\livelink{chap:flag}{flag}
1147 \addtoindexx{mutable attribute!encoding} \\
1149 \livelink{chap:DWATthreadsscaled}{DW\-\_AT\-\_threads\-\_scaled}&0x62&\livelink{chap:flag}{flag}
1150 \addtoindexx{thread scaled attribute!encoding} \\
1151 \livelink{chap:DWATexplicit}{DW\-\_AT\-\_explicit}&0x63&\livelink{chap:flag}{flag}
1152 \addtoindexx{explicit attribute!encoding} \\
1153 \livelink{chap:DWATobjectpointer}{DW\-\_AT\-\_object\-\_pointer}&0x64&reference
1154 \addtoindexx{object pointer attribute!encoding} \\
1155 \livelink{chap:DWATendianity}{DW\-\_AT\-\_endianity}&0x65&constant
1156 \addtoindexx{endianity attribute!encoding} \\
1157 \livelink{chap:DWATelemental}{DW\-\_AT\-\_elemental}&0x66&\livelink{chap:flag}{flag}
1158 \addtoindexx{elemental attribute!encoding} \\
1159 \livelink{chap:DWATpure}{DW\-\_AT\-\_pure}&0x67&\livelink{chap:flag}{flag}
1160 \addtoindexx{pure attribute!encoding} \\
1161 \livelink{chap:DWATrecursive}{DW\-\_AT\-\_recursive}&0x68&\livelink{chap:flag}{flag}
1162 \addtoindexx{recursive attribute!encoding} \\
1163 \livelink{chap:DWATsignature}{DW\-\_AT\-\_signature} \ddag &0x69&reference
1164 \addtoindexx{signature attribute!encoding} \\
1165 \livelink{chap:DWATmainsubprogram}{DW\-\_AT\-\_main\-\_subprogram} \ddag &0x6a&\livelink{chap:flag}{flag}
1166 \addtoindexx{main subprogram attribute!encoding} \\
1167 \livelink{chap:DWATdatabitoffset}{DW\-\_AT\-\_data\-\_bit\-\_offset} \ddag &0x6b&constant
1168 \addtoindexx{data bit offset attribute!encoding} \\
1169 \livelink{chap:DWATconstexpr}{DW\-\_AT\-\_const\-\_expr} \ddag &0x6c&\livelink{chap:flag}{flag}
1170 \addtoindexx{constant expression attribute!encoding} \\
1171 \livelink{chap:DWATenumclass}{DW\-\_AT\-\_enum\-\_class} \ddag &0x6d&\livelink{chap:flag}{flag}
1172 \addtoindexx{enumeration class attribute!encoding} \\
1173 \livelink{chap:DWATlinkagename}{DW\-\_AT\-\_linkage\-\_name} \ddag &0x6e&string
1174 \addtoindexx{linkage name attribute!encoding} \\
1175 \livetarg{chap:DWATlouser}{DW\-\_AT\-\_lo\-\_user}&0x2000 & --- \addtoindexx{low user attribute encoding} \\
1176 \livetarg{chap:DWAThiuser}{DW\-\_AT\-\_hi\-\_user}&0x3fff& --- \addtoindexx{high user attribute encoding} \\
1179 \ddag Attribute new in \addtoindex{DWARF Version 4}
1183 \setlength{\extrarowheight}{0.1cm}
1184 \begin{longtable}{l|l|l}
1185 \caption{Attribute form encodings} \label{tab:attributeformencodings} \\
1186 \hline \\ \bfseries Form name&\bfseries Value &\bfseries Classes \\ \hline
1188 \bfseries Form name&\bfseries Value &\bfseries Classes\\ \hline
1190 \hline \emph{Continued on next page}
1194 \livelink{chap:DWFORMaddr}{DW\-\_FORM\-\_addr}&0x01&address \\
1195 \livelink{chap:DWFORMblock2}{DW\-\_FORM\-\_block2}&0x03&\livelink{chap:block}{block} \\
1196 \livelink{chap:DWFORMblock4}{DW\-\_FORM\-\_block4}&0x04&\livelink{chap:block}{block} \\
1197 \livelink{chap:DWFORMdata2}{DW\-\_FORM\-\_data2}&0x05&constant \\
1198 \livelink{chap:DWFORMdata4}{DW\-\_FORM\-\_data4}&0x06&constant \\
1199 \livelink{chap:DWFORMdata8}{DW\-\_FORM\-\_data8}&0x07&constant \\
1200 \livelink{chap:DWFORMstring}{DW\-\_FORM\-\_string}&0x08&string \\
1201 \livelink{chap:DWFORMblock}{DW\-\_FORM\-\_block}&0x09&\livelink{chap:block}{block} \\
1202 \livelink{chap:DWFORMblock1}{DW\-\_FORM\-\_block1}&0x0a&\livelink{chap:block}{block} \\
1203 \livelink{chap:DWFORMdata1}{DW\-\_FORM\-\_data1}&0x0b&constant \\
1204 \livelink{chap:DWFORMflag}{DW\-\_FORM\-\_flag}&0x0c&\livelink{chap:flag}{flag} \\
1205 \livelink{chap:DWFORMsdata}{DW\-\_FORM\-\_sdata}&0x0d&constant \\
1206 \livelink{chap:DWFORMstrp}{DW\-\_FORM\-\_strp}&0x0e&string \\
1207 \livelink{chap:DWFORMudata}{DW\-\_FORM\-\_udata}&0x0f&constant \\
1208 \livelink{chap:DWFORMrefaddr}{DW\-\_FORM\-\_ref\-\_addr}&0x10&reference \\
1209 \livelink{chap:DWFORMref1}{DW\-\_FORM\-\_ref1}&0x11&reference \\
1210 \livelink{chap:DWFORMref2}{DW\-\_FORM\-\_ref2}&0x12&reference \\
1211 \livelink{chap:DWFORMref4}{DW\-\_FORM\-\_ref4}&0x13&reference \\
1212 \livelink{chap:DWFORMref8}{DW\-\_FORM\-\_ref8}&0x14&reference \\
1213 \livelink{chap:DWFORMrefudata}{DW\-\_FORM\-\_ref\-\_udata}&0x15&reference \\
1214 \livelink{chap:DWFORMindirect}{DW\-\_FORM\-\_indirect}&0x16&(see Section \refersec{datarep:abbreviationstables}) \\
1215 \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} \\
1216 \livelink{chap:DWFORMexprloc}{DW\-\_FORM\-\_exprloc} \ddag &0x18&\livelink{chap:exprloc}{exprloc} \\
1217 \livelink{chap:DWFORMflagpresent}{DW\-\_FORM\-\_flag\-\_present} \ddag &0x19&\livelink{chap:flag}{flag} \\
1218 \livelink{chap:DWFORMrefsig8}{DW\-\_FORM\-\_ref\-\_sig8} \ddag &0x20&reference \\
1221 \ddag FORM new in \addtoindex{DWARF Version 4}
1224 \section{Variable Length Data}
1225 \label{datarep:variablelengthdata}
1226 \addtoindexx{variable length data|see {LEB128}}
1228 \addtoindexx{Little Endian Base 128|see{LEB128}}
1229 encoded using ``Little Endian Base 128''
1230 \addtoindexx{little-endian encoding|see{endian attribute}}
1232 \addtoindexx{LEB128}
1233 LEB128 is a scheme for encoding integers
1234 densely that exploits the assumption that most integers are
1237 This encoding is equally suitable whether the target machine
1238 architecture represents data in big\dash\ endian or little\dash endian
1239 order. It is ``little\dash endian'' only in the sense that it
1240 avoids using space to represent the ``big'' end of an
1241 unsigned integer, when the big end is all zeroes or sign
1244 Unsigned LEB128 (ULEB128) numbers are encoded as follows:
1245 \addtoindexx{LEB128!unsigned, encoding as}
1246 start at the low order end of an unsigned integer and chop
1247 it into 7\dash bit chunks. Place each chunk into the low order 7
1248 bits of a byte. Typically, several of the high order bytes
1249 will be zero; discard them. Emit the remaining bytes in a
1250 stream, starting with the low order byte; set the high order
1251 bit on each byte except the last emitted byte. The high bit
1252 of zero on the last byte indicates to the decoder that it
1253 has encountered the last byte.
1255 The integer zero is a special case, consisting of a single
1258 Table \refersec{tab:examplesofunsignedleb128encodings}
1259 gives some examples of unsigned LEB128 numbers. The
1260 0x80 in each case is the high order bit of the byte, indicating
1261 that an additional byte follows.
1264 The encoding for signed, two’s complement LEB128 (SLEB128)
1265 \addtoindexx{LEB128!signed, encoding as}
1266 numbers is similar, except that the criterion for discarding
1267 high order bytes is not whether they are zero, but whether
1268 they consist entirely of sign extension bits. Consider the
1269 32\dash bit integer -2. The three high level bytes of the number
1270 are sign extension, thus LEB128 would represent it as a single
1271 byte containing the low order 7 bits, with the high order
1272 bit cleared to indicate the end of the byte stream. Note
1273 that there is nothing within the LEB128 representation that
1274 indicates whether an encoded number is signed or unsigned. The
1275 decoder must know what type of number to expect.
1276 Table \refersec{tab:examplesofunsignedleb128encodings}
1277 gives some examples of unsigned LEB128 numbers and
1278 Table \refersec{tab:examplesofsignedleb128encodings}
1279 gives some examples of signed LEB128
1282 Appendix \refersec{app:variablelengthdataencodingdecodinginformative}
1283 \addtoindexx{LEB128!examples}
1284 gives algorithms for encoding and decoding these forms.
1288 \setlength{\extrarowheight}{0.1cm}
1289 \begin{longtable}{l|l|l}
1290 \caption{Examples of unsigned LEB128 encodings} \label{tab:examplesofunsignedleb128encodings} \\
1291 \hline \\ \bfseries Number&\bfseries First byte &\bfseries Second byte \\ \hline
1293 \bfseries Number&\bfseries First Byte &\bfseries Second byte\\ \hline
1295 \hline \emph{Continued on next page}
1301 128& 0 + 0x80 & 1 \\
1302 129& 1 + 0x80 & 1 \\
1303 130& 2 + 0x80 & 1 \\
1304 12857& 57 + 0x80 & 100 \\
1305 \addtoindex{LEB128 encoding!examples}
1312 \setlength{\extrarowheight}{0.1cm}
1313 \begin{longtable}{l|l|l}
1314 \caption{Examples of signed LEB128 encodings} \label{tab:examplesofsignedleb128encodings} \\
1315 \hline \\ \bfseries Number&\bfseries First byte &\bfseries Second byte \\ \hline
1317 \bfseries Number&\bfseries First Byte &\bfseries Second byte\\ \hline
1319 \hline \emph{Continued on next page}
1325 127& 127 + 0x80 & 0 \\
1326 -127& 1 + 0x80 & 0x7f \\
1327 128& 0 + 0x80 & 1 \\
1328 -128& 0 + 0x80 & 0x7f \\
1329 129& 1 + 0x80 & 1 \\
1330 -129& -x7f + 0x80 & 0xtc \\
1337 \section{DWARF Expressions and Location Descriptions}
1338 \label{datarep:dwarfexpressionsandlocationdescriptions}
1339 \subsection{DWARF Expressions}
1340 \label{datarep:dwarfexpressions}
1343 \addtoindexx{DWARF Expression!operator encoding}
1344 DWARF expression is stored in a \nolink{block} of contiguous
1345 bytes. The bytes form a sequence of operations. Each operation
1346 is a 1\dash byte code that identifies that operation, followed by
1347 zero or more bytes of additional data. The encodings for the
1348 operations are described in
1349 Table \refersec{tab:dwarfoperationencodings}.
1352 \setlength{\extrarowheight}{0.1cm}
1353 \begin{longtable}{l|l|l|l}
1354 \caption{DWARF operation encodings} \label{tab:dwarfoperationencodings} \\
1355 \hline \\ & &\bfseries No. of &\\
1356 \bfseries Operation&\bfseries Code &\bfseries Operands &\bfseries Notes\\ \hline
1358 & &\bfseries No. of &\\
1359 \bfseries Operation&\bfseries Code &\bfseries Operands &\bfseries Notes\\ \hline
1361 \hline \emph{Continued on next page}
1366 \livelink{chap:DWOPaddr}{DW\-\_OP\-\_addr}&0x03&1 & constant address \\
1367 & & &(size target specific) \\
1369 \livelink{chap:DWOPderef}{DW\-\_OP\-\_deref}&0x06&0 & \\
1372 \livelink{chap:DWOPconst1u}{DW\-\_OP\-\_const1u}&0x08&1&1\dash byte constant \\
1373 \livelink{chap:DWOPconst1s}{DW\-\_OP\-\_const1s}&0x09&1&1\dash byte constant \\
1374 \livelink{chap:DWOPconst2u}{DW\-\_OP\-\_const2u}&0x0a&1&2\dash byte constant \\
1375 \livelink{chap:DWOPconst2s}{DW\-\_OP\-\_const2s}&0x0b&1&2\dash byte constant \\
1376 \livelink{chap:DWOPconst4u}{DW\-\_OP\-\_const4u}&0x0c&1&4\dash byte constant \\
1377 \livelink{chap:DWOPconst4s}{DW\-\_OP\-\_const4s}&0x0d&1&4\dash byte constant \\
1378 \livelink{chap:DWOPconst8u}{DW\-\_OP\-\_const8u}&0x0e&1&8\dash byte constant \\
1379 \livelink{chap:DWOPconst8s}{DW\-\_OP\-\_const8s}&0x0f&1&8\dash byte constant \\
1380 \livelink{chap:DWOPconstu}{DW\-\_OP\-\_constu}&0x10&1&ULEB128 constant \\
1381 \livelink{chap:DWOPconsts}{DW\-\_OP\-\_consts}&0x11&1&SLEB128 constant \\
1382 \livelink{chap:DWOPdup}{DW\-\_OP\-\_dup}&0x12&0 & \\
1383 \livelink{chap:DWOPdrop}{DW\-\_OP\-\_drop}&0x13&0 & \\
1384 \livelink{chap:DWOPover}{DW\-\_OP\-\_over}&0x14&0 & \\
1385 \livelink{chap:DWOPpick}{DW\-\_OP\-\_pick}&0x15&1&1\dash byte stack index \\
1386 \livelink{chap:DWOPswap}{DW\-\_OP\-\_swap}&0x16&0 & \\
1387 \livelink{chap:DWOProt}{DW\-\_OP\-\_rot}&0x17&0 & \\
1388 \livelink{chap:DWOPxderef}{DW\-\_OP\-\_xderef}&0x18&0 & \\
1389 \livelink{chap:DWOPabs}{DW\-\_OP\-\_abs}&0x19&0 & \\
1390 \livelink{chap:DWOPand}{DW\-\_OP\-\_and}&0x1a&0 & \\
1391 \livelink{chap:DWOPdiv}{DW\-\_OP\-\_div}&0x1b&0 & \\
1395 \livelink{chap:DWOPminus}{DW\-\_OP\-\_minus}&0x1c&0 & \\
1396 \livelink{chap:DWOPmod}{DW\-\_OP\-\_mod}&0x1d&0 & \\
1397 \livelink{chap:DWOPmul}{DW\-\_OP\-\_mul}&0x1e&0 & \\
1398 \livelink{chap:DWOPneg}{DW\-\_OP\-\_neg}&0x1f&0 & \\
1399 \livelink{chap:DWOPnot}{DW\-\_OP\-\_not}&0x20&0 & \\
1400 \livelink{chap:DWOPor}{DW\-\_OP\-\_or}&0x21&0 & \\
1401 \livelink{chap:DWOPplus}{DW\-\_OP\-\_plus}&0x22&0 & \\
1402 \livelink{chap:DWOPplusuconst}{DW\-\_OP\-\_plus\-\_uconst}&0x23&1&ULEB128 addend \\
1403 \livelink{chap:DWOPshl}{DW\-\_OP\-\_shl}&0x24&0 & \\
1404 \livelink{chap:DWOPshr}{DW\-\_OP\-\_shr}&0x25&0 & \\
1405 \livelink{chap:DWOPshra}{DW\-\_OP\-\_shra}&0x26&0 & \\
1406 \livelink{chap:DWOPxor}{DW\-\_OP\-\_xor}&0x27&0 & \\
1407 \livelink{chap:DWOPskip}{DW\-\_OP\-\_skip}&0x2f&1&signed 2\dash byte constant \\
1408 \livelink{chap:DWOPbra}{DW\-\_OP\-\_bra}&0x28&1 & signed 2\dash byte constant \\
1409 \livelink{chap:DWOPeq}{DW\-\_OP\-\_eq}&0x29&0 & \\
1410 \livelink{chap:DWOPge}{DW\-\_OP\-\_ge}&0x2a&0 & \\
1411 \livelink{chap:DWOPgt}{DW\-\_OP\-\_gt}&0x2b&0 & \\
1412 \livelink{chap:DWOPle}{DW\-\_OP\-\_le}&0x2c&0 & \\
1413 \livelink{chap:DWOPlt}{DW\-\_OP\-\_lt}&0x2d&0 & \\
1414 \livelink{chap:DWOPne}{DW\-\_OP\-\_ne}&0x2e&0 & \\ \hline
1418 \livelink{chap:DWOPlit0}{DW\-\_OP\-\_lit0}&0x30 & 0 & \\
1420 \livelink{chap:DWOPlit1}{DW\-\_OP\-\_lit1}&0x31 & 0& literals 0 .. 31 = \\
1421 \ldots & & & (\livelink{chap:DWOPlit0}{DW\-\_OP\-\_lit0} + literal) \\
1422 \livelink{chap:DWOPlit31}{DW\-\_OP\-\_lit31}&0x4f & 0 & \\ \hline
1424 \livelink{chap:DWOPreg0}{DW\-\_OP\-\_reg0} & 0x50 & 0 & \\
1425 \livelink{chap:DWOPreg1}{DW\-\_OP\-\_reg1} & 0x51 & 0® 0 .. 31 = \\
1426 \ldots & & & (\livelink{chap:DWOPreg0}{DW\-\_OP\-\_reg0} + regnum) \\
1427 \livelink{chap:DWOPreg31}{DW\-\_OP\-\_reg31} & 0x6f & 0 & \\ \hline
1429 \livelink{chap:DWOPbreg0}{DW\-\_OP\-\_breg0} & 0x70 &1 & SLEB128 offset \\
1430 \livelink{chap:DWOPbreg1}{DW\-\_OP\-\_breg1} & 0x71 & 1 &base register 0 .. 31 = \\
1431 ... & & &(\livelink{chap:DWOPbreg0}{DW\-\_OP\-\_breg0} + regnum) \\
1432 \livelink{chap:DWOPbreg31}{DW\-\_OP\-\_breg31} & 0x8f & 1 & \\ \hline
1434 \livelink{chap:DWOPregx}{DW\-\_OP\-\_regx} & 0x90 &1&ULEB128 register \\
1435 \livelink{chap:DWOPfbreg}{DW\-\_OP\-\_fbreg} & 0x91&1&SLEB128 offset \\
1436 \livelink{chap:DWOPbregx}{DW\-\_OP\-\_bregx} & 0x92&2 &ULEB128 register followed \\
1437 & & & by SLEB128 offset \\
1438 \livelink{chap:DWOPpiece}{DW\-\_OP\-\_piece} & 0x93 &1& ULEB128 size of piece addressed \\
1439 \livelink{chap:DWOPderefsize}{DW\-\_OP\-\_deref\-\_size} & 0x94 &1& 1-byte size of data retrieved \\
1440 \livelink{chap:DWOPxderefsize}{DW\-\_OP\-\_xderef\-\_size} & 0x95&1&1-byte size of data retrieved \\
1441 \livelink{chap:DWOPnop}{DW\-\_OP\-\_nop} & 0x96 &0& \\
1444 \livelink{chap:DWOPpushobjectaddress}{DW\-\_OP\-\_push\-\_object\-\_address}&0x97&0 & \\
1445 \livelink{chap:DWOPcall2}{DW\-\_OP\-\_call2}&0x98&1& 2\dash byte offset of DIE \\
1446 \livelink{chap:DWOPcall4}{DW\-\_OP\-\_call4}&0x99&1& 4\dash byte offset of DIE \\
1447 \livelink{chap:DWOPcallref}{DW\-\_OP\-\_call\-\_ref}&0x9a&1& 4\dash\ or 8\dash byte\\
1448 &&& offset of DIE \\
1449 \livelink{chap:DWOPformtlsaddress}{DW\-\_OP\-\_form\-\_tls\-\_address}&0x9b &0& \\
1450 \livelink{chap:DWOPcallframecfa}{DW\-\_OP\-\_call\-\_frame\-\_cfa} &0x9c &0& \\
1451 \livelink{chap:DWOPbitpiece}{DW\-\_OP\-\_bit\-\_piece}&0x9d &2&ULEB128 size followed by \\
1453 \livelink{chap:DWOPimplicitvalue}{DW\-\_OP\-\_implicit\-\_value}&0x9e &2&ULEB128 size followed by \\
1454 &&&\nolink{block} of that size\\
1455 \livelink{chap:DWOPstackvalue}{DW\-\_OP\-\_stack\-\_value} &0x9f &0& \\
1456 \livetarg{chap:DWOPlouser}{DW\-\_OP\-\_lo\-\_user} &0xe0 && \\
1457 \livetarg{chap:DWOPhiuser}{DW\-\_OP\-\_hi\-\_user} &0xff && \\
1463 \subsection{Location Descriptions}
1464 \label{datarep:locationdescriptions}
1466 A location description is used to compute the
1467 location of a variable or other entity.
1469 \subsection{Location Lists}
1470 \label{datarep:locationlists}
1472 Each entry in a \addtoindex{location list} is either a location list entry,
1473 a base address selection entry, or an
1474 \addtoindex{end of list entry!in location list}
1477 A \addtoindex{location list} entry consists of two address offsets followed
1478 by a 2\dash byte length, followed by a block of contiguous bytes
1479 that contains a DWARF location description. The length
1480 specifies the number of bytes in that block. The two offsets
1481 are the same size as an address on the target machine.
1483 A base address selection entry and an
1484 \addtoindex{end of list entry!in location list}
1485 end of list entry each
1486 consist of two (constant or relocated) address offsets. The two
1487 offsets are the same size as an address on the target machine.
1489 For a \addtoindex{location list} to be specified, the base address of
1490 \addtoindexx{base address selection entry!in location list}
1491 the corresponding compilation unit must be defined
1492 (see Section \refersec{chap:normalandpartialcompilationunitentries}).
1494 \section{Base Type Attribute Encodings}
1495 \label{datarep:basetypeattributeencodings}
1497 The encodings of the
1498 \hypertarget{chap:DWATencodingencodingofbasetype}
1500 \addtoindexx{encoding attribute!encoding}
1502 \livelink{chap:DWATencoding}{DW\-\_AT\-\_encoding}
1503 attribute are given in
1504 Table \refersec{tab:basetypeencodingvalues}
1507 \setlength{\extrarowheight}{0.1cm}
1508 \begin{longtable}{l|c}
1509 \caption{Base type encoding values} \label{tab:basetypeencodingvalues} \\
1510 \hline \\ \bfseries Base type encoding code name&\bfseries Value \\ \hline
1512 \bfseries Base type encoding code name&\bfseries Value\\ \hline
1514 \hline \emph{Continued on next page}
1519 \livelink{chap:DWATEaddress}{DW\-\_ATE\-\_address}&0x01 \\
1520 \livelink{chap:DWATEboolean}{DW\-\_ATE\-\_boolean}&0x02 \\
1521 \livelink{chap:DWATEcomplexfloat}{DW\-\_ATE\-\_complex\-\_float}&0x03 \\
1522 \livelink{chap:DWATEfloat}{DW\-\_ATE\-\_float}&0x04 \\
1523 \livelink{chap:DWATEsigned}{DW\-\_ATE\-\_signed}&0x05 \\
1524 \livelink{chap:DWATEsignedchar}{DW\-\_ATE\-\_signed\-\_char}&0x06 \\
1525 \livelink{chap:DWATEunsigned}{DW\-\_ATE\-\_unsigned}&0x07 \\
1526 \livelink{chap:DWATEunsignedchar}{DW\-\_ATE\-\_unsigned\-\_char}&0x08 \\
1527 \livelink{chap:DWATEimaginaryfloat}{DW\-\_ATE\-\_imaginary\-\_float}&0x09 \\
1528 \livelink{chap:DWATEpackeddecimal}{DW\-\_ATE\-\_packed\-\_decimal}&0x0a \\
1529 \livelink{chap:DWATEnumericstring}{DW\-\_ATE\-\_numeric\-\_string}&0x0b \\
1530 \livelink{chap:DWATEedited}{DW\-\_ATE\-\_edited}&0x0c \\
1531 \livelink{chap:DWATEsignedfixed}{DW\-\_ATE\-\_signed\-\_fixed}&0x0d \\
1532 \livelink{chap:DWATEunsignedfixed}{DW\-\_ATE\-\_unsigned\-\_fixed}&0x0e \\
1533 \livelink{chap:DWATEdecimalfloat}{DW\-\_ATE\-\_decimal\-\_float} & 0x0f \\
1534 \livelink{chap:DWATEUTF}{DW\-\_ATE\-\_UTF} \ddag & 0x10 \\
1535 \livetarg{chap:DWATElouser}{DW\-\_ATE\-\_lo\-\_user} & 0x80 \\
1536 \livetarg{chap:DWATEhiuser}{DW\-\_ATE\-\_hi\-\_user} & 0xff \\
1539 \ddag Base type encoding new in \addtoindex{DWARF Version 4}
1543 The encodings of the constants used in the
1544 \livelink{chap:DWATdecimalsign}{DW\-\_AT\-\_decimal\-\_sign} attribute
1546 Table \refersec{tab:decimalsignencodings}.
1550 \setlength{\extrarowheight}{0.1cm}
1551 \begin{longtable}{l|c}
1552 \caption{Decimal sign encodings} \label{tab:decimalsignencodings} \\
1553 \hline \\ \bfseries Decimal sign code name&\bfseries Value \\ \hline
1555 \bfseries Decimal sign code name&\bfseries Value\\ \hline
1557 \hline \emph{Continued on next page}
1562 \livelink{chap:DWDSunsigned}{DW\-\_DS\-\_unsigned} & 0x01 \\
1563 \livelink{chap:DWDSleadingoverpunch}{DW\-\_DS\-\_leading\-\_overpunch} & 0x02 \\
1564 \livelink{chap:DWDStrailingoverpunch}{DW\-\_DS\-\_trailing\-\_overpunch} & 0x03 \\
1565 \livelink{chap:DWDSleadingseparate}{DW\-\_DS\-\_leading\-\_separate} & 0x04 \\
1566 \livelink{chap:DWDStrailingseparate}{DW\-\_DS\-\_trailing\-\_separate} & 0x05 \\
1571 The encodings of the constants used in the
1572 \livelink{chap:DWATendianity}{DW\-\_AT\-\_endianity} attribute are given in
1573 Table \refersec{tab:endianityencodings}.
1576 \setlength{\extrarowheight}{0.1cm}
1577 \begin{longtable}{l|c}
1578 \caption{Endianity encodings} \label{tab:endianityencodings}\\
1579 \hline \\ \bfseries Endian code name&\bfseries Value \\ \hline
1581 \bfseries Endian code name&\bfseries Value\\ \hline
1583 \hline \emph{Continued on next page}
1588 \livelink{chap:DWENDdefault}{DW\-\_END\-\_default} & 0x00 \\
1589 \livelink{chap:DWENDbig}{DW\-\_END\-\_big} & 0x01 \\
1590 \livelink{chap:DWENDlittle}{DW\-\_END\-\_little} & 0x02 \\
1591 \livetarg{chap:DWENDlouser}{DW\-\_END\-\_lo\-\_user} & 0x40 \\
1592 \livetarg{chap:DWENDhiuser}{DW\-\_END\-\_hi\-\_user} & 0xff \\
1597 \section{Accessibility Codes}
1598 \label{datarep:accessibilitycodes}
1599 The encodings of the constants used in the
1600 \livelink{chap:DWATaccessibility}{DW\-\_AT\-\_accessibility}
1602 \addtoindexx{accessibility attribute!encoding}
1604 Table \refersec{tab:accessibilityencodings}.
1607 \setlength{\extrarowheight}{0.1cm}
1608 \begin{longtable}{l|c}
1609 \caption{Accessibility encodings} \label{tab:accessibilityencodings}\\
1610 \hline \\ \bfseries Accessibility code name&\bfseries Value \\ \hline
1612 \bfseries Accessibility code name&\bfseries Value\\ \hline
1614 \hline \emph{Continued on next page}
1619 \livelink{chap:DWACCESSpublic}{DW\-\_ACCESS\-\_public}&0x01 \\
1620 \livelink{chap:DWACCESSprotected}{DW\-\_ACCESS\-\_protected}&0x02 \\
1621 \livelink{chap:DWACCESSprivate}{DW\-\_ACCESS\-\_private}&0x03 \\
1627 \section{Visibility Codes}
1628 \label{datarep:visibilitycodes}
1629 The encodings of the constants used in the
1630 \livelink{chap:DWATvisibility}{DW\-\_AT\-\_visibility} attribute are given in
1631 Table \refersec{tab:visibilityencodings}.
1634 \setlength{\extrarowheight}{0.1cm}
1635 \begin{longtable}{l|c}
1636 \caption{Visibility encodings} \label{tab:visibilityencodings}\\
1637 \hline \\ \bfseries Visiibility code name&\bfseries Value \\ \hline
1639 \bfseries Visibility code name&\bfseries Value\\ \hline
1641 \hline \emph{Continued on next page}
1646 \livelink{chap:DWVISlocal}{DW\-\_VIS\-\_local}&0x01 \\
1647 \livelink{chap:DWVISexported}{DW\-\_VIS\-\_exported}&0x02 \\
1648 \livelink{chap:DWVISqualified}{DW\-\_VIS\-\_qualified}&0x03 \\
1653 \section{Virtuality Codes}
1654 \label{datarep:vitualitycodes}
1656 The encodings of the constants used in the
1657 \livelink{chap:DWATvirtuality}{DW\-\_AT\-\_virtuality} attribute are given in
1658 Table \refersec{tab:virtualityencodings}.
1661 \setlength{\extrarowheight}{0.1cm}
1662 \begin{longtable}{l|c}
1663 \caption{Virtuality encodings} \label{tab:virtualityencodings}\\
1664 \hline \\ \bfseries Virtuality code name&\bfseries Value \\ \hline
1666 \bfseries Virtuality code name&\bfseries Value\\ \hline
1668 \hline \emph{Continued on next page}
1673 \livelink{chap:DWVIRTUALITYnone}{DW\-\_VIRTUALITY\-\_none}&0x00 \\
1674 \livelink{chap:DWVIRTUALITYvirtual}{DW\-\_VIRTUALITY\-\_virtual}&0x01 \\
1675 \livelink{chap:DWVIRTUALITYpurevirtual}{DW\-\_VIRTUALITY\-\_pure\-\_virtual}&0x02 \\
1683 \livelink{chap:DWVIRTUALITYnone}{DW\-\_VIRTUALITY\-\_none} is equivalent to the absence of the
1684 \livelink{chap:DWATvirtuality}{DW\-\_AT\-\_virtuality}
1687 \section{Source Languages}
1688 \label{datarep:sourcelanguages}
1690 The encodings of the constants used
1691 \addtoindexx{language attribute, encoding}
1693 \addtoindexx{language name encoding}
1695 \livelink{chap:DWATlanguage}{DW\-\_AT\-\_language}
1696 attribute are given in
1697 Table \refersec{tab:languageencodings}.
1699 % If we don't force a following space it looks odd
1701 and their associated values are reserved, but the
1702 languages they represent are not well supported.
1703 Table \refersec{tab:languageencodings}
1705 \addtoindexx{lower bound attribute!default}
1706 default lower bound, if any, assumed for
1707 an omitted \livelink{chap:DWATlowerbound}{DW\-\_AT\-\_lower\-\_bound} attribute in the context of a
1708 \livelink{chap:DWTAGsubrangetype}{DW\-\_TAG\-\_subrange\-\_type} debugging information entry for each
1712 \setlength{\extrarowheight}{0.1cm}
1713 \begin{longtable}{l|c|c}
1714 \caption{Language encodings} \label{tab:languageencodings}\\
1715 \hline \\ \bfseries Language name&\bfseries Value &\bfseries Default Lower Bound \\ \hline
1717 \bfseries Language name&\bfseries Value &\bfseries Default Lower Bound\\ \hline
1719 \hline \emph{Continued on next page}
1724 \livelink{chap:DWLANGC89}{DW\-\_LANG\-\_C89}&0x0001&0 \\
1725 \livelink{chap:DWLANGC}{DW\-\_LANG\-\_C}&0x0002&0 \\
1726 \livelink{chap:DWLANGAda83}{DW\-\_LANG\-\_Ada83} \dag &0x0003&1 \addtoindexx{Ada} \\
1727 \livelink{chap:DWLANGCplusplus}{DW\-\_LANG\-\_C\-\_plus\-\_plus} &0x0004&0 \\
1728 \livelink{chap:DWLANGCobol74}{DW\-\_LANG\-\_Cobol74} \dag &0x0005&1 \\
1729 \livelink{chap:DWLANGCobol85}{DW\-\_LANG\-\_Cobol85} \dag &0x0006&1 \\
1730 \livelink{chap:DWLANGFortran77}{DW\-\_LANG\-\_Fortran77}&0x0007&1 \\
1731 \livelink{chap:DWLANGFortran90}{DW\-\_LANG\-\_Fortran90}&0x0008&1 \\
1732 \livelink{chap:DWLANGPascal83}{DW\-\_LANG\-\_Pascal83}&0x0009&1 \\
1733 \livelink{chap:DWLANGModula2}{DW\-\_LANG\-\_Modula2}&0x000a&1 \\
1734 \livelink{chap:DWLANGJava}{DW\-\_LANG\-\_Java}&0x000b&0 \\
1735 \livelink{chap:DWLANGC99}{DW\-\_LANG\-\_C99}&0x000c&0 \\
1736 \livelink{chap:DWLANGAda95}{DW\-\_LANG\-\_Ada95} \dag &0x000d&1 \addtoindexx{Ada} \\
1737 \livelink{chap:DWLANGFortran95}{DW\-\_LANG\-\_Fortran95} &0x000e&1 \\
1738 \livelink{chap:DWLANGPLI}{DW\-\_LANG\-\_PLI} \dag &0x000f&1 \\
1739 \livelink{chap:DWLANGObjC}{DW\-\_LANG\-\_ObjC}&0x0010&0 \\
1740 \livelink{chap:DWLANGObjCplusplus}{DW\-\_LANG\-\_ObjC\-\_plus\-\_plus}&0x0011&0 \\
1741 \livelink{chap:DWLANGUPC}{DW\-\_LANG\-\_UPC}&0x0012&0 \\
1742 \livelink{chap:DWLANGD}{DW\-\_LANG\-\_D}&0x0013&0 \\
1743 \livelink{chap:DWLANGPython}{DW\-\_LANG\-\_Python} \dag &0x0014&0 \\
1744 \livetarg{chap:DWLANGlouser}{DW\-\_LANG\-\_lo\-\_user}&0x8000 & \\
1745 \livetarg{chap:DWLANGhiuser}{DW\-\_LANG\-\_hi\-\_user}&0xffff & \\
1751 \section{Address Class Encodings}
1752 \label{datarep:addressclassencodings}
1754 The value of the common
1755 \addtoindexi{address}{address class!attribute encoding}
1757 \livelink{chap:DWADDRnone}{DW\-\_ADDR\-\_none} is 0.
1760 \section{Identifier Case}
1761 \label{datarep:identifiercase}
1763 The encodings of the constants used in the
1764 \livelink{chap:DWATidentifiercase}{DW\-\_AT\-\_identifier\-\_case} attribute are given in
1765 Table \refersec{tab:identifiercaseencodings}.
1768 \setlength{\extrarowheight}{0.1cm}
1769 \begin{longtable}{l|c}
1770 \caption{Identifier case encodings} \label{tab:identifiercaseencodings}\\
1771 \hline \\ \bfseries Identifier case name&\bfseries Value \\ \hline
1773 \bfseries Identifier case name&\bfseries Value\\ \hline
1775 \hline \emph{Continued on next page}
1779 \livelink{chap:DWIDcasesensitive}{DW\-\_ID\-\_case\-\_sensitive}&0x00 \\
1780 \livelink{chap:DWIDupcase}{DW\-\_ID\-\_up\-\_case}&0x01 \\
1781 \livelink{chap:DWIDdowncase}{DW\-\_ID\-\_down\-\_case}&0x02 \\
1782 \livelink{chap:DWIDcaseinsensitive}{DW\-\_ID\-\_case\-\_insensitive}&0x03 \\
1786 \section{Calling Convention Encodings}
1787 \label{datarep:callingconventionencodings}
1788 The encodings of the constants used in the
1789 \livelink{chap:DWATcallingconvention}{DW\-\_AT\-\_calling\-\_convention} attribute are given in
1790 Table \refersec{tab:callingconventionencodings}.
1793 \setlength{\extrarowheight}{0.1cm}
1794 \begin{longtable}{l|c}
1795 \caption{Calling convention encodings} \label{tab:callingconventionencodings}\\
1796 \hline \\ \bfseries Calling Convention name&\bfseries Value \\ \hline
1798 \bfseries Calling Convention name&\bfseries Value\\ \hline
1800 \hline \emph{Continued on next page}
1805 \livelink{chap:DWCCnormal}{DW\-\_CC\-\_normal}&0x01 \\
1806 \livelink{chap:DWCCprogram}{DW\-\_CC\-\_program}&0x02 \\
1807 \livelink{chap:DWCCnocall}{DW\-\_CC\-\_nocall}&0x03 \\
1808 \livetarg{chap:DWCClouser}{DW\-\_CC\-\_lo\-\_user}&0x40 \\
1809 \livetarg{chap:DWCChiuser}{DW\-\_CC\-\_hi\-\_user}&0xff \\
1814 \section{Inline Codes}
1815 \label{datarep:inlinecodes}
1817 The encodings of the constants used in
1818 \addtoindexx{inline attribute!encoding}
1820 \livelink{chap:DWATinline}{DW\-\_AT\-\_inline} attribute are given in
1821 Table \refersec{tab:inlineencodings}.
1824 \setlength{\extrarowheight}{0.1cm}
1825 \begin{longtable}{l|c}
1826 \caption{Inline encodings} \label{tab:inlineencodings}\\
1827 \hline \\ \bfseries Iline Code name&\bfseries Value \\ \hline
1829 \bfseries Iline Code name&\bfseries Value\\ \hline
1831 \hline \emph{Continued on next page}
1836 \livelink{chap:DWINLnotinlined}{DW\-\_INL\-\_not\-\_inlined}&0x00 \\
1837 \livelink{chap:DWINLinlined}{DW\-\_INL\-\_inlined}&0x01 \\
1838 \livelink{chap:DWINLdeclarednotinlined}{DW\-\_INL\-\_declared\-\_not\-\_inlined}&0x02 \\
1839 \livelink{chap:DWINLdeclaredinlined}{DW\-\_INL\-\_declared\-\_inlined}&0x03 \\
1844 % this clearpage is ugly, but the following table came
1845 % out oddly without it.
1847 \section{Array Ordering}
1848 \label{datarep:arrayordering}
1850 The encodings of the constants used in the
1851 \livelink{chap:DWATordering}{DW\-\_AT\-\_ordering} attribute are given in
1852 Table \refersec{tab:orderingencodings}.
1855 \setlength{\extrarowheight}{0.1cm}
1856 \begin{longtable}{l|c}
1857 \caption{Ordering encodings} \label{tab:orderingencodings}\\
1858 \hline \\ \bfseries Ordering name&\bfseries Value \\ \hline
1860 \bfseries Ordering name&\bfseries Value\\ \hline
1862 \hline \emph{Continued on next page}
1867 \livelink{chap:DWORDrowmajor}{DW\-\_ORD\-\_row\-\_major}&0x00 \\
1868 \livelink{chap:DWORDcolmajor}{DW\-\_ORD\-\_col\-\_major}&0x01 \\
1874 \section{Discriminant Lists}
1875 \label{datarep:discriminantlists}
1877 The descriptors used in
1878 \addtoindexx{discriminant list attribute!encoding}
1880 \livelink{chap:DWATdiscrlist}{DW\-\_AT\-\_discr\-\_list} attribute are
1881 encoded as 1\dash byte constants. The
1882 defined values are given in
1883 Table \refersec{tab:discriminantdescriptorencodings}.
1885 % Odd that the 'Name' field captalized here, it is not caps elsewhere.
1887 \setlength{\extrarowheight}{0.1cm}
1888 \begin{longtable}{l|c}
1889 \caption{Discriminant descriptor encodings} \label{tab:discriminantdescriptorencodings}\\
1890 \hline \\ \bfseries Descriptor Name&\bfseries Value \\ \hline
1892 \bfseries Descriptor Name&\bfseries Value\\ \hline
1894 \hline \emph{Continued on next page}
1899 \livetarg{chap:DWDSClabel}{DW\-\_DSC\-\_label}&0x00 \\
1900 \livetarg{chap:DWDSCrange}{DW\-\_DSC\-\_range}&0x01 \\
1905 \section{Name Lookup Tables}
1906 \label{datarep:namelookuptables}
1908 Each set of entries in the table of global names contained
1909 in the \addtoindex{.debug\_pubnames} and
1910 \addtoindex{.debug\_pubtypes} sections begins
1911 with a header consisting of:
1914 \begin{enumerate}[1.]
1915 \item unit\_length (initial length) \\
1916 A 4\dash byte or 12\dash byte unsigned integer
1917 \addtoindexx{initial length}
1918 representing the length
1919 of the \addtoindex{.debug\_info}
1920 contribution for that compilation unit,
1921 not including the length field itself. In the 32\dash bit DWARF
1922 format, this is a 4\dash byte unsigned integer (which must be less
1923 than 0xfffffff0); in the 64\dash bit DWARF format, this consists
1924 of the 4\dash byte value 0xffffffff followed by an 8\dash byte unsigned
1925 integer that gives the actual length
1926 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
1928 \item version (uhalf)
1929 A 2\dash byte unsigned integer representing the version of the
1930 DWARF information\addtoindexx{version number!compilation unit} for the compilation unit
1931 \addtoindexx{version number!name lookup table}
1932 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
1933 The value in this field is 4.
1935 % Some say unsigned offset this just says offset: FIXME
1936 \item \addtoindex{debug\_info\_offset} (section offset) \\
1938 \addtoindexx{section offset!in name lookup table set of entries}
1939 4\dash byte or 8\dash byte
1941 \addtoindex{.debug\_info}
1942 section of the compilation unit header.
1944 the 32\dash bit DWARF format, this is a 4\dash byte unsigned offset;
1945 in the 64\dash bit DWARF format, this is an 8\dash byte unsigned offsets
1946 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
1948 \item \addtoindex{debug\_info\_length} (section length) \\
1949 \addtoindexx{section length!in .debug\_pubnames header}
1951 \addtoindexx{section length!in .debug\_pubtypes header}
1952 4\dash byte or 8\dash byte length containing the size in bytes of the
1953 contents of the \addtoindex{.debug\_info}
1954 section generated to represent
1955 this compilation unit. In the 32\dash bit DWARF format, this is
1956 a 4\dash byte unsigned length; in the 64\dash bit DWARF format, this
1957 is an 8-byte unsigned length
1958 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
1963 This header is followed by a series of tuples. Each tuple
1964 consists of a 4\dash byte or 8\dash byte offset followed by a string
1965 of non\dash null bytes terminated by one null byte.
1967 DWARF format, this is a 4\dash byte offset; in the 64\dash bit DWARF
1968 format, it is an 8\dash byte offset.
1969 Each set is terminated by an
1970 offset containing the value 0.
1973 \section{Address Range Table}
1974 \label{datarep:addrssrangetable}
1976 Each set of entries in the table of address ranges contained
1977 in the \addtoindex{.debug\_aranges}
1978 section begins with a header containing:
1980 \begin{enumerate}[1.]
1981 % FIXME The unit length text is not fully consistent across
1984 \item unit\_length (initial length) \\
1985 A 4-byte or 12-byte length containing the length of the
1986 \addtoindexx{initial length}
1987 set of entries for this compilation unit, not including the
1988 length field itself. In the 32-bit DWARF format, this is a
1989 4-byte unsigned integer (which must be less than 0xfffffff0);
1990 in the 64-bit DWARF format, this consists of the 4-byte value
1991 0xffffffff followed by an 8-byte unsigned integer that gives
1993 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
1995 \item version (uhalf) \\
1996 A 2\dash byte version identifier
1997 \addtoindexx{version number!address range table} containing the value 2
1998 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
2000 \item debug\_info\_offset (section offset) \\
2002 \addtoindexx{section offset!in .debug\_aranges header}
2003 4\dash byte or 8\dash byte offset into the
2004 \addtoindex{.debug\_info} section of
2005 the compilation unit header. In the 32\dash bit DWARF format,
2006 this is a 4\dash byte unsigned offset; in the 64\dash bit DWARF format,
2007 this is an 8\dash byte unsigned offset
2008 (see Section \refersec{datarep:32bitand64bitdwarfformats}).
2010 \item address\_size (ubyte) \\
2011 A 1\dash byte unsigned integer containing the size in bytes of an
2012 \addtoindexx{address\_size}
2014 \addtoindexx{size of an address}
2015 (or the offset portion of an address for segmented
2016 \addtoindexx{address space!segmented}
2017 addressing) on the target system.
2019 \item segment\_size (ubyte) \\
2021 \addtoindexx{segment\_size}
2022 1\dash byte unsigned integer containing the size in bytes of a
2023 segment selector on the target system.
2027 This header is followed by a series of tuples. Each tuple
2028 consists of a segment, an address and a length.
2030 size is given by the \addtoindex{segment\_size} field of the header; the
2031 address and length size are each given by the address\_size
2032 field of the header.
2033 The first tuple following the header in
2034 each set begins at an offset that is a multiple of the size
2035 of a single tuple (that is, the size of a segment selector
2036 plus twice the \addtoindex{size of an address}).
2037 The header is padded, if
2038 necessary, to that boundary. Each set of tuples is terminated
2039 by a 0 for the segment, a 0 for the address and 0 for the
2040 length. If the \addtoindex{segment\_size} field in the header is zero,
2041 the segment selectors are omitted from all tuples, including
2042 the terminating tuple.
2045 \section{Line Number Information}
2046 \label{datarep:linenumberinformation}
2048 The \addtoindexi{version number}{version number!line number information}
2049 in the line number program header is 4
2050 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
2052 The boolean values ``true'' and ``false''
2053 used by the line number information program are encoded
2054 as a single byte containing the value 0
2055 for ``false,'' and a non-zero value for ``true.''
2057 The encodings for the standard opcodes are given in
2058 \addtoindexx{line number opcodes!standard opcode encoding}
2059 Table \refersec{tab:linenumberstandardopcodeencodings}.
2061 % Odd that the 'Name' field captalized here, it is not caps elsewhere.
2063 \setlength{\extrarowheight}{0.1cm}
2064 \begin{longtable}{l|c}
2065 \caption{Line Number Standard Opcode encodings} \label{tab:linenumberstandardopcodeencodings}\\
2066 \hline \\ \bfseries Opcode Name&\bfseries Value \\ \hline
2068 \bfseries Opcode Name&\bfseries Value\\ \hline
2070 \hline \emph{Continued on next page}
2075 \livelink{chap:DWLNScopy}{DW\-\_LNS\-\_copy}&0x01 \\
2076 \livelink{chap:DWLNSadvancepc}{DW\-\_LNS\-\_advance\-\_pc}&0x02 \\
2077 \livelink{chap:DWLNSadvanceline}{DW\-\_LNS\-\_advance\-\_line}&0x03 \\
2078 \livelink{chap:DWLNSsetfile}{DW\-\_LNS\-\_set\-\_file}&0x04 \\
2079 \livelink{chap:DWLNSsetcolumn}{DW\-\_LNS\-\_set\-\_column}&0x05 \\
2080 \livelink{chap:DWLNSnegatestmt}{DW\-\_LNS\-\_negate\-\_stmt}&0x06 \\
2081 \livelink{chap:DWLNSsetbasicblock}{DW\-\_LNS\-\_set\-\_basic\-\_block}&0x07 \\
2082 \livelink{chap:DWLNSconstaddpc}{DW\-\_LNS\-\_const\-\_add\-\_pc}*0x08 \\
2083 \livelink{chap:DWLNSfixedadvancepc}{DW\-\_LNS\-\_fixed\-\_advance\-\_pc}&0x09 \\
2084 \livelink{chap:DWLNSsetprologueend}{DW\-\_LNS\-\_set\-\_prologue\-\_end}&0x0a \\
2085 \livelink{chap:DWLNSsetepiloguebegin}{DW\-\_LNS\-\_set\-\_epilogue\-\_begin}&0x0b \\
2086 \livelink{chap:DWLNSsetisa}{DW\-\_LNS\-\_set\-\_isa}&0x0c \\
2092 The encodings for the extended opcodes are given in
2093 \addtoindexx{line number opcodes!extended opcode encoding}
2094 Table \refersec{tab:linenumberextendedopcodeencodings}.
2097 \setlength{\extrarowheight}{0.1cm}
2098 \begin{longtable}{l|c}
2099 \caption{Line Number Extended Opcode encodings} \label{tab:linenumberextendedopcodeencodings}\\
2100 \hline \\ \bfseries Opcode Name&\bfseries Value \\ \hline
2102 \bfseries Opcode Name&\bfseries Value\\ \hline
2104 \hline \emph{Continued on next page}
2109 \livelink{chap:DWLNEendsequence}{DW\-\_LNE\-\_end\-\_sequence}&0x01 \\
2110 \livelink{chap:DWLNEsetaddress}{DW\-\_LNE\-\_set\-\_address}&0x02\\
2111 \livelink{chap:DWLNEdefinefile}{DW\-\_LNE\-\_define\-\_file}&0x03\\
2112 \livelink{chap:DWLNEsetdiscriminator}{DW\-\_LNE\-\_set\-\_discriminator} \ddag &0x04 \\
2113 \livetarg{chap:DWLNElouser}{DW\-\_LNE\-\_lo\-\_user}&0x80 \\
2114 \livetarg{chap:DWLNEhiuser}{DW\-\_LNE\-\_hi\-\_user}&0xff \\
2117 \ddag Extended opcode new in \addtoindex{DWARF Version 4}.
2120 \section{Macro Information}
2121 \label{datarep:macroinformation}
2123 The source line numbers and source file indices encoded in the
2124 macro information section are represented as unsigned LEB128
2125 numbers as are the constants in a
2126 \livelink{chap:DWMACINFOvendorext}{DW\-\_MACINFO\-\_vendor\-\_ext} entry.
2128 The macinfo type is encoded as a single byte.
2130 \addtoindexx{macinfo types!encoding}
2132 Table \refersec{tab:macinfotypeencodings}.
2136 \setlength{\extrarowheight}{0.1cm}
2137 \begin{longtable}{l|c}
2138 \caption{Macinfo Type Encodings} \label{tab:macinfotypeencodings}\\
2139 \hline \\ \bfseries Macinfo Type Name&\bfseries Value \\ \hline
2141 \bfseries Macinfo Type Name&\bfseries Value\\ \hline
2143 \hline \emph{Continued on next page}
2148 \livelink{chap:DWMACINFOdefine}{DW\-\_MACINFO\-\_define}&0x01 \\
2149 \livelink{chap:DWMACINFOundef}{DW\-\_MACINFO\-\_undef}&0x02 \\
2150 \livelink{chap:DWMACINFOstartfile}{DW\-\_MACINFO\-\_start\-\_file}&0x03 \\
2151 \livelink{chap:DWMACINFOendfile}{DW\-\_MACINFO\-\_end\-\_file}&0x04 \\
2152 \livelink{chap:DWMACINFOvendorext}{DW\-\_MACINFO\-\_vendor\-\_ext}&0xff \\
2157 \section{Call Frame Information}
2158 \label{datarep:callframeinformation}
2160 In the 32\dash bit DWARF format, the value of the CIE id in the
2161 CIE header is 0xffffffff; in the 64\dash bit DWARF format, the
2162 value is 0xffffffffffffffff.
2164 The value of the CIE \addtoindexi{version number}{version number!call frame information}
2165 is 4 (see Appendix \refersec{app:dwarfsectionversionnumbersinformative}).
2167 Call frame instructions are encoded in one or more bytes. The
2168 primary opcode is encoded in the high order two bits of
2169 the first byte (that is, opcode = byte >> 6). An operand
2170 or extended opcode may be encoded in the low order 6
2171 bits. Additional operands are encoded in subsequent bytes.
2172 The instructions and their encodings are presented in
2173 Table \refersec{tab:callframeinstructionencodings}.
2176 \setlength{\extrarowheight}{0.1cm}
2177 \begin{longtable}{l|c|c|l|l}
2178 \caption{Call frame instruction encodings} \label{tab:callframeinstructionencodings} \\
2179 \hline \\ &\bfseries High 2 &\bfseries Low 6 & & \\
2180 \bfseries Instruction&\bfseries Bits &\bfseries Bits &\bfseries Operand 1 &\bfseries Operand 2\\ \hline
2182 & \bfseries High 2 &\bfseries Low 6 & &\\
2183 \bfseries Instruction&\bfseries Bits &\bfseries Bits &\bfseries Operand 1 &\bfseries Operand 2\\ \hline
2185 \hline \emph{Continued on next page}
2190 \livelink{chap:DWCFAadvanceloc}{DW\-\_CFA\-\_advance\-\_loc}&0x1&delta & \\
2191 \livelink{chap:DWCFAoffset}{DW\-\_CFA\-\_offset}&0x2®ister&ULEB128 offset \\
2192 \livelink{chap:DWCFArestore}{DW\-\_CFA\-\_restore}&0x3®ister & & \\
2193 \livelink{chap:DWCFAnop}{DW\-\_CFA\-\_nop}&0&0 & & \\
2194 \livelink{chap:DWCFAsetloc}{DW\-\_CFA\-\_set\-\_loc}&0&0x01&address & \\
2195 \livelink{chap:DWCFAadvanceloc1}{DW\-\_CFA\-\_advance\-\_loc1}&0&0x02&1\dash byte delta & \\
2196 \livelink{chap:DWCFAadvanceloc2}{DW\-\_CFA\-\_advance\-\_loc2}&0&0x03&2\dash byte delta & \\
2197 \livelink{chap:DWCFAadvanceloc4}{DW\-\_CFA\-\_advance\-\_loc4}&0&0x04&4\dash byte delta & \\
2198 \livelink{chap:DWCFAoffsetextended}{DW\-\_CFA\-\_offset\-\_extended}&0&0x05&ULEB128 register&ULEB128 offset \\
2199 \livelink{chap:DWCFArestoreextended}{DW\-\_CFA\-\_restore\-\_extended}&0&0x06&ULEB128 register & \\
2200 \livelink{chap:DWCFAundefined}{DW\-\_CFA\-\_undefined}&0&0x07&ULEB128 register & \\
2201 \livelink{chap:DWCFAsamevalue}{DW\-\_CFA\-\_same\-\_value}&0&0x08 &ULEB128 register & \\
2202 \livelink{chap:DWCFAregister}{DW\-\_CFA\-\_register}&0&0x09&ULEB128 register &ULEB128 offset \\
2203 \livelink{chap:DWCFArememberstate}{DW\-\_CFA\-\_remember\-\_state}&0&0x0a & & \\
2204 \livelink{chap:DWCFArestorestate}{DW\-\_CFA\-\_restore\-\_state}&0&0x0b & & \\
2205 \livelink{chap:DWCFAdefcfa}{DW\-\_CFA\-\_def\-\_cfa}&0&0x0c &ULEB128 register&ULEB128 offset \\
2206 \livelink{chap:DWCFAdefcfaregister}{DW\-\_CFA\-\_def\-\_cfa\-\_register}&0&0x0d&ULEB128 register & \\
2207 \livelink{chap:DWCFAdefcfaoffset}{DW\-\_CFA\-\_def\-\_cfa\-\_offset}&0&0x0e &ULEB128 offset & \\
2208 \livelink{chap:DWCFAdefcfaexpression}{DW\-\_CFA\-\_def\-\_cfa\-\_expression}&0&0x0f &BLOCK \\
2209 \livelink{chap:DWCFAexpression}{DW\-\_CFA\-\_expression}&0&0x10&ULEB128 register & BLOCK \\
2211 \livelink{chap:DWCFAoffsetextendedsf}{DW\-\_CFA\-\_offset\-\_extended\-\_sf}&0&0x11&ULEB128 register&SLEB128 offset \\
2212 \livelink{chap:DWCFAdefcfasf}{DW\-\_CFA\-\_def\-\_cfa\-\_sf}&0&0x12&ULEB128 register&SLEB128 offset \\
2213 \livelink{chap:DWCFAdefcfaoffsetsf}{DW\-\_CFA\-\_def\-\_cfa\-\_offset\-\_sf}&0&0x13&SLEB128 offset & \\
2214 \livelink{chap:DWCFAvaloffset}{DW\-\_CFA\-\_val\-\_offset}&0&0x14&ULEB128&ULEB128 \\
2215 \livelink{chap:DWCFAvaloffsetsf}{DW\-\_CFA\-\_val\-\_offset\-\_sf}&0&0x15&ULEB128&SLEB128 \\
2216 \livelink{chap:DWCFAvalexpression}{DW\-\_CFA\-\_val\-\_expression}&0&0x16&ULEB128&BLOCK \\
2217 \livetarg{chap:DWCFAlouser}{DW\-\_CFA\-\_lo\-\_user}&0&0x1c & & \\
2218 \livetarg{chap:DWCFAhiuser}{DW\-\_CFA\-\_hi\-\_user}&0&0x3f & & \\
2222 \section{Non-continguous Address Ranges}
2223 \label{datarep:noncontiguousaddressranges}
2225 Each entry in a \addtoindex{range list}
2226 (see Section \refersec{chap:noncontiguousaddressranges})
2228 \addtoindexx{base address selection entry!in range list}
2230 \addtoindexx{range list}
2231 a base address selection entry, or an end
2234 A \addtoindex{range list} entry consists of two relative addresses. The
2235 addresses are the same size as addresses on the target machine.
2237 A base address selection entry and an
2238 \addtoindex{end of list entry!in range list}
2239 end of list entry each
2240 \addtoindexx{base address selection entry!in range list}
2241 consist of two (constant or relocated) addresses. The two
2242 addresses are the same size as addresses on the target machine.
2244 For a \addtoindex{range list} to be specified, the base address of the
2245 \addtoindexx{base address selection entry!in range list}
2246 corresponding compilation unit must be defined
2247 (see Section \refersec{chap:normalandpartialcompilationunitentries}).
2250 \section{Dependencies and Constraints}
2251 \label{datarep:dependenciesandconstraints}
2253 The debugging information in this format is intended to
2255 \addtoindexx{DWARF section names!list of}
2257 the \addtoindex{.debug\_abbrev},
2258 \addtoindex{.debug\_aranges},
2259 \addtoindex{.debug\_frame},
2260 \addtoindex{.debug\_info},
2261 \addtoindex{.debug\_line},
2262 \addtoindex{.debug\_loc},
2263 \addtoindex{.debug\_macinfo},
2264 \addtoindex{.debug\_pubnames},
2265 \addtoindex{.debug\_pubtypes},
2266 \addtoindex{.debug\_ranges},
2267 \addtoindex{.debug\_str}
2269 \addtoindex{.debug\_types}
2270 sections of an object file, or equivalent
2271 separate file or database. The information is not
2272 word\dash aligned. Consequently: •
2275 \item For the 32\dash bit DWARF format and a target architecture with
2276 32\dash bit addresses, an assembler or compiler must provide a way
2277 to produce 2\dash byte and 4\dash byte quantities without alignment
2278 restrictions, and the linker must be able to relocate a
2279 4\dash byte address or
2280 \addtoindexx{section offset!alignment of}
2281 section offset that occurs at an arbitrary
2284 \item For the 32\dash bit DWARF format and a target architecture with
2285 64\dash bit addresses, an assembler or compiler must provide a
2286 way to produce 2\dash byte, 4\dash byte and 8\dash byte quantities without
2287 alignment restrictions, and the linker must be able to relocate
2288 an 8\dash byte address or 4\dash byte
2289 \addtoindexx{section offset!alignment of}
2290 section offset that occurs at an
2291 arbitrary alignment.
2293 \item For the 64\dash bit DWARF format and a target architecture with
2294 32\dash bit addresses, an assembler or compiler must provide a
2295 way to produce 2\dash byte, 4\dash byte and 8\dash byte quantities without
2296 alignment restrictions, and the linker must be able to relocate
2297 a 4\dash byte address or 8\dash byte
2298 \addtoindexx{section offset!alignment of}
2299 section offset that occurs at an
2300 arbitrary alignment.
2302 \textit{It is expected that this will be required only for very large
2303 32\dash bit programs or by those architectures which support
2304 a mix of 32\dash bit and 64\dash bit code and data within the same
2307 \item For the 64\dash bit DWARF format and a target architecture with
2308 64\dash bit addresses, an assembler or compiler must provide a
2309 way to produce 2\dash byte, 4\dash byte and 8\dash byte quantities without
2310 alignment restrictions, and the linker must be able to
2311 relocate an 8\dash byte address or
2312 \addtoindexx{section offset!alignment of}
2313 section offset that occurs at
2314 an arbitrary alignment.
2317 \section{Integer Representation Names}
2318 \label{datarep:integerrepresentationnames}
2320 The sizes of the integers used in the lookup by name, lookup
2321 by address, line number and call frame information sections
2323 Table 41 \refersec{tab:integerrepresentationnames}.
2326 \setlength{\extrarowheight}{0.1cm}
2327 \begin{longtable}{c|l}
2328 \caption{Integer Representation Names} \label{tab:integerrepresentationnames}\\
2329 \hline \\ \bfseries Representation Name&\bfseries Representation \\ \hline
2331 \bfseries Representation Name&\bfseries Representation\\ \hline
2333 \hline \emph{Continued on next page}
2338 \addtoindex{sbyte}& signed, 1\dash byte integer \\
2339 \addtoindex{ubyte}&unsigned, 1\dash byte integer \\
2340 \addtoindex{uhalf}&unsigned, 2\dash byte integer \\
2341 \addtoindex{uword}&unsigned, 4\dash byte integer \\
2346 \section{Type Signature Computation}
2347 \label{datarep:typesignaturecomputation}
2349 A type signature is computed only by the DWARF producer;
2350 it is used by a DWARF consumer to resolve type references to
2351 the type definitions that are contained in type units.
2353 The type signature for a type T0 is formed from the
2354 \addtoindex{MD5 hash}
2355 of a flattened description of the type. The flattened
2356 description of the type is a byte sequence derived from the
2357 DWARF encoding of the type as follows:
2359 \begin{enumerate}[1.]
2361 \item Start with an empty sequence S and a list V of visited
2362 types, where V is initialized to a list containing the type
2363 T0 as its single element. Elements in V are indexed from 1,
2366 \item If the debugging information entry represents a type that
2367 is nested inside another type or a namespace, append to S
2368 the type’s context as follows: For each surrounding type
2369 or namespace, beginning with the outermost such construct,
2370 append the letter 'C', the DWARF tag of the construct, and
2371 the name (taken from
2372 \addtoindexx{name attribute}
2373 the \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute) of the type
2374 \addtoindexx{name attribute}
2375 or namespace (including its trailing null byte).
2377 \item Append to S the letter 'D', followed by the DWARF tag of
2378 the debugging information entry.
2380 \item For each of the following attributes that are present in
2381 the debugging information entry, in the order listed below,
2382 append to S a marker letter (see below), the DWARF attribute
2383 code, and the attribute value.
2386 \item \livelink{chap:DWATname}{DW\-\_AT\-\_name}
2387 \item \livelink{chap:DWATaccessibility}{DW\-\_AT\-\_accessibility}
2388 \item \livelink{chap:DWATaddressclass}{DW\-\_AT\-\_address\-\_class}
2389 \item \livelink{chap:DWATallocated}{DW\-\_AT\-\_allocated}
2390 \item \livelink{chap:DWATartificial}{DW\-\_AT\-\_artificial}
2391 \item \livelink{chap:DWATassociated}{DW\-\_AT\-\_associated}
2392 \item \livelink{chap:DWATbinaryscale}{DW\-\_AT\-\_binary\-\_scale}
2393 \item \livelink{chap:DWATbitoffset}{DW\-\_AT\-\_bit\-\_offset}
2394 \item \livelink{chap:DWATbitsize}{DW\-\_AT\-\_bit\-\_size}
2395 \item \livelink{chap:DWATbitstride}{DW\-\_AT\-\_bit\-\_stride}
2396 \item \livelink{chap:DWATbytesize}{DW\-\_AT\-\_byte\-\_size}
2397 \item \livelink{chap:DWATbytestride}{DW\-\_AT\-\_byte\-\_stride}
2398 \item \livelink{chap:DWATconstexpr}{DW\-\_AT\-\_const\-\_expr}
2399 \item \livelink{chap:DWATconstvalue}{DW\-\_AT\-\_const\-\_value}
2400 \item \livelink{chap:DWATcontainingtype}{DW\-\_AT\-\_containing\-\_type}
2401 \item \livelink{chap:DWATcount}{DW\-\_AT\-\_count}
2402 \item \livelink{chap:DWATdatabitoffset}{DW\-\_AT\-\_data\-\_bit\-\_offset}
2403 \item \livelink{chap:DWATdatalocation}{DW\-\_AT\-\_data\-\_location}
2404 \item \livelink{chap:DWATdatamemberlocation}{DW\-\_AT\-\_data\-\_member\-\_location}
2405 \item \livelink{chap:DWATdecimalscale}{DW\-\_AT\-\_decimal\-\_scale}
2406 \item \livelink{chap:DWATdecimalsign}{DW\-\_AT\-\_decimal\-\_sign}
2407 \item \livelink{chap:DWATdefaultvalue}{DW\-\_AT\-\_default\-\_value}
2408 \item \livelink{chap:DWATdigitcount}{DW\-\_AT\-\_digit\-\_count}
2409 \item \livelink{chap:DWATdiscr}{DW\-\_AT\-\_discr}
2410 \item \livelink{chap:DWATdiscrlist}{DW\-\_AT\-\_discr\-\_list}
2411 \item \livelink{chap:DWATdiscrvalue}{DW\-\_AT\-\_discr\-\_value}
2412 \item \livelink{chap:DWATencoding}{DW\-\_AT\-\_encoding}
2413 \item \livelink{chap:DWATenumclass}{DW\-\_AT\-\_enum\-\_class}
2414 \item \livelink{chap:DWATendianity}{DW\-\_AT\-\_endianity}
2415 \item \livelink{chap:DWATexplicit}{DW\-\_AT\-\_explicit}
2416 \item \livelink{chap:DWATisoptional}{DW\-\_AT\-\_is\-\_optional}
2417 \item \livelink{chap:DWATlocation}{DW\-\_AT\-\_location}
2418 \item \livelink{chap:DWATlowerbound}{DW\-\_AT\-\_lower\-\_bound}
2419 \item \livelink{chap:DWATmutable}{DW\-\_AT\-\_mutable}
2420 \item \livelink{chap:DWATordering}{DW\-\_AT\-\_ordering}
2421 \item \livelink{chap:DWATpicturestring}{DW\-\_AT\-\_picture\-\_string}
2422 \item \livelink{chap:DWATprototyped}{DW\-\_AT\-\_prototyped}
2423 \item \livelink{chap:DWATsmall}{DW\-\_AT\-\_small}
2424 \item \livelink{chap:DWATsegment}{DW\-\_AT\-\_segment}
2425 \item \livelink{chap:DWATstringlength}{DW\-\_AT\-\_string\-\_length}
2426 \item \livelink{chap:DWATthreadsscaled}{DW\-\_AT\-\_threads\-\_scaled}
2427 \item \livelink{chap:DWATupperbound}{DW\-\_AT\-\_upper\-\_bound}
2428 \item \livelink{chap:DWATuselocation}{DW\-\_AT\-\_use\-\_location}
2429 \item \livelink{chap:DWATuseUTF8}{DW\-\_AT\-\_use\-\_UTF8}
2430 \item \livelink{chap:DWATvariableparameter}{DW\-\_AT\-\_variable\-\_parameter}
2431 \item \livelink{chap:DWATvirtuality}{DW\-\_AT\-\_virtuality}
2432 \item \livelink{chap:DWATvisibility}{DW\-\_AT\-\_visibility}
2433 \item \livelink{chap:DWATvtableelemlocation}{DW\-\_AT\-\_vtable\-\_elem\-\_location}
2436 Note that except for the initial
2437 \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute,
2438 \addtoindexx{name attribute}
2439 attributes are appended in order according to the alphabetical
2440 spelling of their identifier.
2442 If an implementation defines any vendor-specific attributes,
2443 any such attributes that are essential to the definition of
2444 the type should also be included at the end of the above list,
2445 in their own alphabetical suborder.
2447 An attribute that refers to another type entry T is processed
2448 as follows: (a) If T is in the list V at some V[x], use the
2449 letter 'R' as the marker and use the unsigned LEB128 encoding
2450 of x as the attribute value; otherwise, (b) use the letter 'T'
2451 as the marker, process the type T recursively by performing
2452 Steps 2 through 7, and use the result as the attribute value.
2454 Other attribute values use the letter 'A' as the marker, and
2455 the value consists of the form code (encoded as an unsigned
2456 LEB128 value) followed by the encoding of the value according
2457 to the form code. To ensure reproducibility of the signature,
2458 the set of forms used in the signature computation is limited
2459 to the following: \livelink{chap:DWFORMsdata}{DW\-\_FORM\-\_sdata},
2460 \livelink{chap:DWFORMflag}{DW\-\_FORM\-\_flag},
2461 \livelink{chap:DWFORMstring}{DW\-\_FORM\-\_string},
2462 and \livelink{chap:DWFORMblock}{DW\-\_FORM\-\_block}.
2464 \item If the tag in Step 3 is one of \livelink{chap:DWTAGpointertype}{DW\-\_TAG\-\_pointer\-\_type},
2465 \livelink{chap:DWTAGreferencetype}{DW\-\_TAG\-\_reference\-\_type},
2466 \livelink{chap:DWTAGrvaluereferencetype}{DW\-\_TAG\-\_rvalue\-\_reference\-\_type},
2467 \livelink{chap:DWTAGptrtomembertype}{DW\-\_TAG\-\_ptr\-\_to\-\_member\-\_type},
2468 or \livelink{chap:DWTAGfriend}{DW\-\_TAG\-\_friend}, and the referenced
2469 type (via the \livelink{chap:DWATtype}{DW\-\_AT\-\_type} or
2470 \livelink{chap:DWATfriend}{DW\-\_AT\-\_friend} attribute) has a
2471 \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute, append to S the letter 'N', the DWARF
2472 attribute code (\livelink{chap:DWATtype}{DW\-\_AT\-\_type} or
2473 \livelink{chap:DWATfriend}{DW\-\_AT\-\_friend}), the context of
2474 the type (according to the method in Step 2), the letter 'E',
2475 and the name of the type. For \livelink{chap:DWTAGfriend}{DW\-\_TAG\-\_friend}, if the referenced
2476 entry is a \livelink{chap:DWTAGsubprogram}{DW\-\_TAG\-\_subprogram}, the context is omitted and the
2477 name to be used is the ABI-specific name of the subprogram
2478 (e.g., the mangled linker name).
2481 \item 6.If the tag in Step 3 is not one of \livelink{chap:DWTAGpointertype}{DW\-\_TAG\-\_pointer\-\_type},
2482 \livelink{chap:DWTAGreferencetype}{DW\-\_TAG\-\_reference\-\_type},
2483 \livelink{chap:DWTAGrvaluereferencetype}{DW\-\_TAG\-\_rvalue\-\_reference\-\_type},
2484 \livelink{chap:DWTAGptrtomembertype}{DW\-\_TAG\-\_ptr\-\_to\-\_member\-\_type}, or
2485 \livelink{chap:DWTAGfriend}{DW\-\_TAG\-\_friend}, but has
2486 a \livelink{chap:DWATtype}{DW\-\_AT\-\_type} attribute, or if the referenced type (via
2487 the \livelink{chap:DWATtype}{DW\-\_AT\-\_type} or
2488 \livelink{chap:DWATfriend}{DW\-\_AT\-\_friend} attribute) does not have a
2489 \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute, the attribute is processed according to
2490 the method in Step 4 for an attribute that refers to another
2494 \item Visit each child C of the debugging information
2495 entry as follows: If C is a nested type entry or a member
2496 function entry, and has
2497 a \livelink{chap:DWATname}{DW\-\_AT\-\_name} attribute, append to
2498 \addtoindexx{name attribute}
2499 S the letter 'S', the tag of C, and its name; otherwise,
2500 process C recursively by performing Steps 3 through 7,
2501 appending the result to S. Following the last child (or if
2502 there are no children), append a zero byte.
2507 For the purposes of this algorithm, if a debugging information
2509 \livelink{chap:DWATspecification}{DW\-\_AT\-\_specification}
2510 attribute that refers to
2511 another entry D (which has a
2512 \livelink{chap:DWATdeclaration}{DW\-\_AT\-\_declaration}
2514 then S inherits the attributes and children of D, and S is
2515 processed as if those attributes and children were present in
2516 the entry S. Exception: if a particular attribute is found in
2517 both S and D, the attribute in S is used and the corresponding
2518 one in D is ignored.
2520 DWARF tag and attribute codes are appended to the sequence
2521 as unsigned LEB128 values, using the values defined earlier
2524 \textit{A grammar describing this computation may be found in
2525 Appendix \refersec{app:typesignaturecomputationgrammar}.
2528 \textit{An attribute that refers to another type entry should
2529 be recursively processed or replaced with the name of the
2530 referent (in Step 4, 5 or 6). If neither treatment applies to
2531 an attribute that references another type entry, the entry
2532 that contains that attribute should not be considered for a
2533 separate type unit.}
2535 \textit{If a debugging information entry contains an attribute from
2536 the list above that would require an unsupported form, that
2537 entry should not be considered for a separate type unit.}
2539 \textit{A type should be considered for a separate type unit only
2540 if all of the type entries that it contains or refers to in
2541 Steps 6 and 7 can themselves each be considered for a separate
2544 Where the DWARF producer may reasonably choose two or more
2545 different forms for a given attribute, it should choose
2546 the simplest possible form in computing the signature. (For
2547 example, a constant value should be preferred to a location
2548 expression when possible.)
2550 Once the string S has been formed from the DWARF encoding,
2551 an \addtoindex{MD5 hash} is computed for the string and the lower 64 bits
2552 are taken as the type signature.
2554 \textit{The string S is intended to be a flattened representation of
2555 the type that uniquely identifies that type (i.e., a different
2556 type is highly unlikely to produce the same string).}
2558 \textit{A debugging information entry should not be placed in a
2559 separate type unit if any of the following apply:}
2563 \item \textit{The entry has an attribute whose value is a location
2564 expression, and the location expression contains a reference to
2565 another debugging information entry (e.g., a \livelink{chap:DWOPcallref}{DW\-\_OP\-\_call\-\_ref}
2566 operator), as it is unlikely that the entry will remain
2567 identical across compilation units.}
2569 \item \textit{The entry has an attribute whose value refers
2570 to a code location or a \addtoindex{location list}.}
2572 \item \textit{The entry has an attribute whose value refers
2573 to another debugging information entry that does not represent
2578 \textit{Certain attributes are not included in the type signature:}
2581 \item \textit{The \livelink{chap:DWATdeclaration}{DW\-\_AT\-\_declaration} attribute is not included because it
2582 indicates that the debugging information entry represents an
2583 incomplete declaration, and incomplete declarations should
2584 not be placed in separate type units.}
2586 \item \textit{The \livelink{chap:DWATdescription}{DW\-\_AT\-\_description} attribute is not included because
2587 it does not provide any information unique to the defining
2588 declaration of the type.}
2590 \item \textit{The \livelink{chap:DWATdeclfile}{DW\-\_AT\-\_decl\-\_file}, \livelink{chap:DWATdeclline}{DW\-\_AT\-\_decl\-\_line}, and
2591 \livelink{chap:DWATdeclcolumn}{DW\-\_AT\-\_decl\-\_column} attributes are not included because they
2592 may vary from one source file to the next, and would prevent
2593 two otherwise identical type declarations from producing the
2594 \addtoindexx{MD5 hash}