diff options
Diffstat (limited to 'contrib/gdb/gdb/doc/stabs.texinfo')
| -rw-r--r-- | contrib/gdb/gdb/doc/stabs.texinfo | 121 |
1 files changed, 68 insertions, 53 deletions
diff --git a/contrib/gdb/gdb/doc/stabs.texinfo b/contrib/gdb/gdb/doc/stabs.texinfo index b0d26c3..1eb9d15 100644 --- a/contrib/gdb/gdb/doc/stabs.texinfo +++ b/contrib/gdb/gdb/doc/stabs.texinfo @@ -14,7 +14,7 @@ END-INFO-DIR-ENTRY @ifinfo This document describes the stabs debugging symbol tables. -Copyright 1992, 1993 Free Software Foundation, Inc. +Copyright 1992, 93, 94, 95, 97, 1998 Free Software Foundation, Inc. Contributed by Cygnus Support. Written by Julia Menapace, Jim Kingdon, and David MacKenzie. @@ -43,7 +43,7 @@ regarded as a program in the language TeX). @page @tex \def\$#1${{#1}} % Kluge: collect RCS revision info without $...$ -\xdef\manvers{\$Revision: 2.125 $} % For use in headers, footers too +\xdef\manvers{\$Revision: 2.128 $} % For use in headers, footers too {\parskip=0pt \hfill Cygnus Support\par \hfill \manvers\par @@ -52,7 +52,7 @@ regarded as a program in the language TeX). @end tex @vskip 0pt plus 1filll -Copyright @copyright{} 1992, 1993 Free Software Foundation, Inc. +Copyright @copyright{} 1992, 93, 94, 95, 97, 1998 Free Software Foundation, Inc. Contributed by Cygnus Support. Permission is granted to make and distribute verbatim copies of @@ -80,8 +80,6 @@ This document describes the stabs debugging format. * Type Descriptors:: Table of type descriptors * Expanded Reference:: Reference information by stab type * Questions:: Questions and anomolies -* Sun Differences:: Differences between GNU stabs and Sun - native stabs * Stab Sections:: In some object file formats, stabs are in sections. * Symbol Types Index:: Index of symbolic stab symbol type names. @@ -240,6 +238,18 @@ type is about to be defined. Any other values following the a number follows the @samp{=} then the number is a @var{type-reference}. For a full description of types, @ref{Types}. +A @var{type-number} is often a single number. The GNU and Sun tools +additionally permit a @var{type-number} to be a pair +(@var{file-number},@var{filetype-number}) (the parentheses appear in the +string, and serve to distinguish the two cases). The @var{file-number} +is a number starting with 1 which is incremented for each seperate +source file in the compilation (e.g., in C, each header file gets a +different number). The @var{filetype-number} is a number starting with +1 which is incremented for each new type defined in the file. +(Separating the file number and the type number permits the +@code{N_BINCL} optimization to succeed more often; see @ref{Include +Files}). + There is an AIX extension for type attributes. Following the @samp{=} are any number of type attributes. Each one starts with @samp{@@} and ends with @samp{;}. Debuggers, including AIX's dbx and GDB 4.10, skip @@ -463,7 +473,7 @@ the start of this one. To specify the main source file again, use an @findex N_EXCL The @code{N_BINCL} approach works as follows. An @code{N_BINCL} symbol specifies the start of an include file. In an object file, only the -string is significant; the Sun linker puts data into some of the other +string is significant; the linker puts data into some of the other fields. The end of the include file is marked by an @code{N_EINCL} symbol (which has no string field). In an object file, there is no significant data in the @code{N_EINCL} symbol. @code{N_BINCL} and @@ -473,16 +483,17 @@ If the linker detects that two source files have identical stabs between an @code{N_BINCL} and @code{N_EINCL} pair (as will generally be the case for a header file), then it only puts out the stabs once. Each additional occurance is replaced by an @code{N_EXCL} symbol. I believe -the Sun (SunOS4, not sure about Solaris) linker is the only one which -supports this feature. - -The SunOS4 linker sets the value of a @code{N_BINCL} symbol to the total -of all the characters in the stabs strings included in the header file, -omitting the file number. The value of an @code{N_EXCL} symbol is the -same as the value of the @code{N_BINCL} symbol it replaces. I do not -know if this information is used by anything. The @code{N_EINCL} value, -and the values of the other and description fields for all three, appear -to always be zero. +the GNU linker and the Sun (both SunOS4 and Solaris) linker are the only +ones which supports this feature. + +A linker which supports this feature will set the value of a +@code{N_BINCL} symbol to the total of all the characters in the stabs +strings included in the header file, omitting any file numbers. The +value of an @code{N_EXCL} symbol is the same as the value of the +@code{N_BINCL} symbol it replaces. This information can be used to +match up @code{N_EXCL} and @code{N_BINCL} symbols which have the same +filename. The @code{N_EINCL} value, and the values of the other and +description fields for all three, appear to always be zero. @findex C_BINCL @findex C_EINCL @@ -632,6 +643,15 @@ group of other stabs describing elements of the procedure. These other stabs describe the procedure's parameters, its block local variables, and its block structure. +If functions can appear in different sections, then the debugger may not +be able to find the end of a function. Recent versions of GCC will mark +the end of a function with an @code{N_FUN} symbol with an empty string +for the name. The value is the address of the end of the current +function. Without such a symbol, there is no indication of the address +of the end of a function, and you must assume that it ended at the +starting address of the next function or at the end of the text section +for the program. + @node Nested Procedures @section Nested Procedures @@ -2060,7 +2080,8 @@ For example, @end example specifies that @code{s_typedef} refers to type number 16. Such stabs -have symbol type @code{N_LSYM} (or @code{C_DECL} for XCOFF). +have symbol type @code{N_LSYM} (or @code{C_DECL} for XCOFF). (The Sun +documentation mentions using @code{N_GSYM} in some cases). If you are specifying the tag name for a structure, union, or enumeration, use the @samp{T} symbol descriptor instead. I believe C is @@ -2669,16 +2690,21 @@ pointer. @node Method Type Descriptor @section The @samp{#} Type Descriptor -This is like the @samp{f} type descriptor for functions (@pxref{Function -Types}), except that a function which uses the @samp{#} type descriptor -takes an extra argument as its first argument, for the @code{this} -pointer. The @samp{#} type descriptor is optionally followed by the -types of the arguments, then another @samp{#}. If the types of the -arguments are omitted, so that the second @samp{#} immediately follows -the @samp{#} which is the type descriptor, the arguments are being -omitted (to save space) and can be deduced from the mangled name of the -method. After the second @samp{#} there is type information for the -return type of the method and a semicolon. +This is used to describe a class method. This is a function which takes +an extra argument as its first argument, for the @code{this} pointer. + +If the @samp{#} is immediately followed by another @samp{#}, the second +one will be followed by the return type and a semicolon. The class and +argument types are not specified, and must be determined by demangling +the name of the method if it is available. + +Otherwise, the single @samp{#} is followed by the class type, a comma, +the return type, a comma, and zero or more parameter types separated by +commas. The list of arguments is terminated by a semicolon. In the +debugging output generated by gcc, a final argument type of @code{void} +indicates a method which does not take a variable number of arguments. +If the final argument type of @code{void} does not appear, the method +was declared with an ellipsis. Note that although such a type will normally be used to describe fields in structures, unions, or classes, for at least some versions of the @@ -3841,25 +3867,6 @@ What ends the procedure scope? Is it the proc block's @code{N_RBRAC} or the next @code{N_FUN}? (I believe its the first.) @end itemize -@node Sun Differences -@appendix Differences Between GNU Stabs and Sun Native Stabs - -@c FIXME: Merge all this stuff into the main body of the document. - -@itemize @bullet -@item -GNU C stabs define @emph{all} types, file or procedure scope, as -@code{N_LSYM}. Sun doc talks about using @code{N_GSYM} too. - -@item -Sun C stabs use type number pairs in the format -(@var{file-number},@var{type-number}) where @var{file-number} is a -number starting with 1 and incremented for each sub-source file in the -compilation. @var{type-number} is a number starting with 1 and -incremented for each new type defined in the compilation. GNU C stabs -use the type number alone, with no source file number. -@end itemize - @node Stab Sections @appendix Using Stabs in Their Own Sections @@ -3928,17 +3935,25 @@ header @code{sh_type} member set to @code{SHT_STRTAB} to mark it as a string table. SOM and COFF have no way of linking the sections together or marking them as string tables. -For COFF, the @code{.stab} and @code{.stabstr} sections are simply +For COFF, the @code{.stab} and @code{.stabstr} sections may be simply concatenated by the linker. GDB then uses the @code{n_desc} fields to figure out the extent of the original sections. Similarly, the @code{n_value} fields of the header symbols are added together in order to get the actual position of the strings in a desired @code{.stabstr} -section. Although this design obviates any need for the linker to relocate -or otherwise manipulate @code{.stab} and @code{.stabstr} sections, it also -requires some care to ensure that the offsets are calculated correctly. -For instance, if the linker were to pad in between the @code{.stabstr} -sections before concatenating, then the offsets to strings in the middle -of the executable's @code{.stabstr} section would be wrong. +section. Although this design obviates any need for the linker to +relocate or otherwise manipulate @code{.stab} and @code{.stabstr} +sections, it also requires some care to ensure that the offsets are +calculated correctly. For instance, if the linker were to pad in +between the @code{.stabstr} sections before concatenating, then the +offsets to strings in the middle of the executable's @code{.stabstr} +section would be wrong. + +The GNU linker is able to optimize stabs information by merging +duplicate strings and removing duplicate header file information +(@pxref{Include Files}). When some versions of the GNU linker optimize +stabs in sections, they remove the leading @code{N_UNDF} symbol and +arranges for all the @code{n_strx} fields to be relative to the start of +the @code{.stabstr} section. @node ELF Linker Relocation @appendixsec Having the Linker Relocate Stabs in ELF |
