* Global Variables:: Variables used by more than one source file.
* Register variables:: Variables in registers.
* Common Blocks:: Variables statically allocated together.
-* Initialized statics:: Static variables with values.
-* Un-initialized statics:: Static variables initialialized to 0.
-* Parameters:: Passing variables to functions.
+* Statics:: Variables local to one source file.
+* Parameters:: Variables for arguments to functions.
@end menu
@node Automatic variables
to a function (that is, if a common block @emph{can} be anything other
than local to a function).
-@node Initialized statics
-@section Initialized static variables
+@node Statics
+@section Static Variables
-@table @strong
-@item Directive:
-@code{.stabs}
-@item Type:
-@code{N_STSYM}
-@item Symbol Descriptors:
-@code{S} (file scope), @code{V} (procedure scope)
-@end table
-
-Initialized static variables are represented by the @code{N_STSYM} stab
-type. The symbol descriptor part of the string field shows if the
-variable is file scope static (@samp{S}) or procedure scope static
-(@samp{V}). The source line
-
-@example
-3 static int s_g_repeat = 2;
-@end example
-
-@noindent
-yields the following code. The stab is located immediately preceding
-the storage for the variable it represents. Since the variable in
-this example is file scope static the symbol descriptor is @samp{S}.
-
-@example
-@exdent @code{N_STSYM} (38): initialized static variable (data seg w/internal linkage)
-
-.stabs "@var{name}:
- @var{descriptor}
- @var{type-ref}",
- N_STSYM,NIL,NIL,
- @var{address}
-
-26 .stabs "s_g_repeat:S1",38,0,0,_s_g_repeat
-27 .align 4
-28 _s_g_repeat:
-29 .word 2
-@end example
-
-
-@node Un-initialized statics
-@section Un-initialized static variables
+Initialized static variables are represented by the @samp{S} and
+@samp{V} symbol descriptors. @samp{S} means file scope static, and
+@samp{V} means procedure scope static.
-@table @strong
-@item Directive:
-@code{.stabs}
-@item Type:
-@code{N_LCSYM}
-@item Symbol Descriptors:
-@code{S} (file scope), @code{V} (procedure scope)
-@end table
+In a.out files, @code{N_STSYM} means the data segment (although gcc
+2.4.5 has a bug in that it uses @code{N_FUN}, so neither dbx nor gdb can
+find the variables), @code{N_FUN} means the text segment, and
+@code{N_LCSYM} means the bss segment.
-Un-initialized static variables are represented by the @code{N_LCSYM}
-stab type. The symbol descriptor part of the string shows if the
-variable is file scope static (@samp{S}) or procedure scope static
-(@samp{V}). In this example it is procedure scope static. The source
-line allocating @code{s_flap} immediately follows the open brace for the
-procedure @code{main}.
-
-@example
-20 @{
-21 static float s_flap;
-@end example
+In xcoff files, each symbol has a section number, so the symbol type
+need not indicate the segment.
-The code that reserves storage for the variable @code{s_flap} precedes the
-body of body of @code{main}.
+@c In ELF files, it apparently is a big mess. See kludge in dbxread.c
+@c in GDB. FIXME: Investigate where this kludge comes from.
+@c
+@c This is the place to mention N_ROSYM; I'd rather do so once I can
+@c coherently explain how this stuff works for stabs-in-elf.
+@c
+For example, the source lines
@example
-39 .reserve _s_flap.0,4,"bss",4
+static const int var_const = 5;
+static int var_init = 2;
+static int var_noinit;
@end example
-But since @code{s_flap} is scoped locally to @code{main}, its stab is
-located with the other stabs representing symbols local to @code{main}.
-The stab for @code{s_flap} is located just before the @code{N_LBRAC} for
-@code{main}.
+@noindent
+yield the following stabs:
@example
-@exdent @code{N_LCSYM} (40): uninitialized static var (BSS seg w/internal linkage)
-
-.stabs "@var{name}:
- @var{descriptor}
- @var{type-ref}",
- N_LCSYM, NIL, NIL,
- @var{address}
-
-97 .stabs "s_flap:V12",40,0,0,_s_flap.0
-98 .stabs "times:1",128,0,0,-20
-99 .stabn 192,0,0,LBB2 # N_LBRAC for main.
+.stabs "var_const:S1",36,0,0,_var_const ; @r{36 = N_FUN}
+. . .
+.stabs "var_init:S1",38,0,0,_var_init ; @r{38 = N_STSYM}
+. . .
+.stabs "var_noinit:S1",40,0,0,_var_noinit ; @r{40 = N_LCSYM}
@end example
-@c ............................................................
-
@node Parameters
@section Parameters
@item 0x22 N_FNAME
Function name (for BSD Fortran), @xref{N_FNAME}.
-@item 0x24 N_FUN
-Function name or text segment variable for C, @xref{N_FUN}.
+@item 0x24 N_FUN
+Function name (@pxref{Procedures}) or text segment variable
+(@pxref{Statics}).
-@item 0x26 N_STSYM
-Static symbol (data segment variable with internal linkage), @xref{N_STSYM}.
+@item 0x26 N_STSYM
+Data segment file-scope variable, @xref{Statics}.
-@item 0x28 N_LCSYM
-.lcomm symbol (BSS segment variable with internal linkage), @xref{N_LCSYM}.
+@item 0x28 N_LCSYM
+BSS segment file-scope variable, @xref{Statics}.
@item 0x2a N_MAIN
Name of main routine, @xref{Main Program}.
Parameter in floating point register, @xref{Parameters}.
@item f
-Static function, @xref{Procedures}.
+File scope function, @xref{Procedures}.
@item F
Global function, @xref{Procedures}.
Register variable, @xref{Register variables}.
@item S
-Static file scope variable @xref{Initialized statics},
-@xref{Un-initialized statics}.
+File scope variable, @xref{Statics}.
@item t
Type name, @xref{Typedefs}.
Parameter passed by reference, @xref{Parameters}.
@item V
-Static procedure scope variable @xref{Initialized statics},
-@xref{Un-initialized statics}.
+Procedure scope static variable, @xref{Statics}.
@item x
Conformant array, @xref{Parameters}.
@menu
* N_GSYM:: Global variable
* N_FNAME:: Function name (BSD Fortran)
-* N_FUN:: C Function name or text segment variable
-* N_STSYM:: Initialized static symbol
-* N_LCSYM:: Uninitialized static symbol
* N_PC:: Pascal global symbol
* N_NSYMS:: Number of symbols
* N_NOMAP:: No DST map
Only the "name" field is significant. The location of the symbol is
obtained from the corresponding extern symbol.
-@node N_FUN
-@section 36 - 0x24 - N_FUN
-
-Function name (@pxref{Procedures}) or text segment variable
-(@pxref{Variables}).
-@example
-@exdent @emph{For functions:}
-"name" -> "proc_name:#return_type"
- # -> F (global function)
- f (local function)
-desc -> line num for proc start. (GCC doesn't set and DBX doesn't miss it.)
-value -> Code address of proc start.
-
-@exdent @emph{For text segment variables:}
-<<How to create one?>>
-@end example
-
-@node N_STSYM
-@section 38 - 0x26 - N_STSYM
-Initialized static symbol (data segment w/internal linkage).
-
-@display
-.stabs "name", N_STSYM, NIL, NIL, value
-@end display
-
-@example
-"name" -> "symbol_name#type"
- # -> S (scope global to compilation unit)
- -> V (scope local to a procedure)
-value -> Data Address
-@end example
-
-@node N_LCSYM
-@section 40 - 0x28 - N_LCSYM
-Unitialized static (.lcomm) symbol(BSS segment w/internal linkage).
-
-@display
-.stabs "name", N_LCLSYM, NIL, NIL, value
-@end display
-
-@example
-"name" -> "symbol_name#type"
- # -> S (scope global to compilation unit)
- -> V (scope local to procedure)
-value -> BSS Address
-@end example
-
@node N_PC
@section 48 - 0x30 - N_PC
Global symbol (for Pascal)
next N_FUN? (I believe its the first.)
@item
-The comment in xcoff.h says DBX_STATIC_CONST_VAR_CODE is used for
-static const variables. DBX_STATIC_CONST_VAR_CODE is set to N_FUN by
-default, in dbxout.c. If included, xcoff.h redefines it to N_STSYM.
-But testing the default behaviour, my Sun4 native example shows
-N_STSYM not N_FUN is used to describe file static initialized
-variables. (the code tests for TREE_READONLY(decl) &&
-!TREE_THIS_VOLATILE(decl) and if true uses DBX_STATIC_CONST_VAR_CODE).
-
-@item
+@c FIXME: This should go with the other stuff about global variables.
Global variable stabs don't have location information. This comes
from the external symbol for the same variable. The external symbol
has a leading underbar on the _name of the variable and the stab does
not. How do we know these two symbol table entries are talking about
-the same symbol when their names are different?
+the same symbol when their names are different? (Answer: the debugger
+knows that external symbols have leading underbars).
+@c FIXME: This is absurdly vague; there all kinds of differences, some
+@c of which are the same between gnu & sun, and some of which aren't.
@item
Can gcc be configured to output stabs the way the Sun compiler
does, so that their native debugging tools work? <NO?> It doesn't by
mapping is N_STABTYPE becomes C_STABTYPE. Some stab types in a.out
are not supported in xcoff. See Table E. for full mappings.
+@c FIXME: Get C_* types for the block, figure out whether it is always
+@c used (I suspect not), explain clearly, and move to node Statics.
exception:
initialised static N_STSYM and un-initialized static N_LCSYM both map
to the C_STSYM storage class. But the destinction is preserved
block. Begin the block with .bs s[RW] data_section_name for N_STSYM
or .bs s bss_section_name for N_LCSYM. End the block with .es
+@c FIXME: I think they are trying to say something about whether the
+@c assembler defaults the value to the location counter.
@item
If the xcoff stab is a N_FUN (C_FUN) then follow the string field with
,. instead of just ,
@end itemize
-
(I think that's it for .s file differences. They could stand to be
better presented. This is just a list of what I have noticed so far.
There are a *lot* of differences in the information in the symbol
projects / binutils-gdb.git / commitdiff