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* stabs.texinfo: Document common blocks.

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Jim Kingdon 1993-06-19 00:45:34 +00:00
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gdb/doc/ChangeLog
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@ -1,3 +1,7 @@
Fri Jun 18 19:42:09 1993 Jim Kingdon (kingdon@lioth.cygnus.com)
* stabs.texinfo: Document common blocks.
Fri Jun 18 12:12:57 1993 Fred Fish (fnf@cygnus.com)
* stabs.texinfo: Add some basic info about stabs-in-elf.

69
gdb/doc/stabs.texinfo
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@ -86,6 +86,7 @@ Appendixes:
and GNU stabs in xcoff
* Sun-differences:: Differences between GNU stabs and Sun
native stabs
* Stabs-in-elf:: Stabs in an ELF file.
@end menu
@end ifinfo
@ -799,12 +800,13 @@ nesting is reflected in the nested bracketing stabs (@code{N_LBRAC},
@chapter Variables
@menu
* Automatic variables:: locally scoped
* Global Variables::
* Register variables::
* Initialized statics::
* Un-initialized statics::
* Parameters::
* Automatic variables:: Variables allocated on the stack.
* Global Variables:: Variables used by more than one source file.
* Common Blocks:: Variables statically allocated together.
* Register variables:: Variables in registers.
* Initialized statics:: Static variables with values.
* Un-initialized statics:: Static variables initialialized to 0.
* Parameters:: Passing variables to functions.
@end menu
@node Automatic variables
@ -929,9 +931,9 @@ number of the register where the variable data will be stored.
The value is the register number.
AIX defines a separate symbol descriptor @samp{d} for floating point
registers. This seems incredibly stupid---why not just just give
floating point registers different register numbers? I have not
verified whether the compiler actually uses @samp{d}.
registers. This seems unnecessary---why not just just give floating
point registers different register numbers? I have not verified whether
the compiler actually uses @samp{d}.
If the register is explicitly allocated to a global variable, but not
initialized, as in
@ -943,6 +945,20 @@ register int g_bar asm ("%g5");
the stab may be emitted at the end of the object file, with
the other bss symbols.
@node Common Blocks
@section Common Blocks
A common block is a statically allocated section of memory which can be
referred to by several source files. It may contain several variables.
I believe @sc{fortran} is the only language with this feature. A
@code{N_BCOMM} stab begins a common block and an @code{N_ECOMM} stab
ends it. The only thing which is significant about these two stabs is
their name, which can be used to look up a normal (non-debugging) symbol
which gives the address of the common block. Each variable in the
common block has a @code{N_ECOML} stab, whose value is the offset within
the common block of that variable. I'm not sure what symbol descriptor
is used for the @code{N_ECOML} stabs.
@node Initialized statics
@section Initialized static variables
@ -3096,13 +3112,13 @@ Modula2 scope information (Sun linker), @xref{N_SCOPE}.
End of a lexical block, @xref{Block Structure}.
@item 0xe2 N_BCOMM
Begin named common block, @xref{N_BCOMM}.
Begin named common block, @xref{Common Blocks}.
@item 0xe4 N_ECOMM
End named common block, @xref{N_ECOMM}.
End named common block, @xref{Common Blocks}.
@item 0xe8 N_ECOML
End common (local name), @xref{N_ECOML}.
Member of a common block, @xref{Common Blocks}.
@c FIXME: How does this really work? Move it to main body of document.
@item 0xea N_WITH
@ -3409,9 +3425,6 @@ Finally, any further information.
* N_LSYM:: Automatic variable
* N_ENTRY:: Alternate entry point
* N_SCOPE:: Modula2 scope information (Sun only)
* N_BCOMM:: Begin named common block
* N_ECOMM:: End named common block
* N_ECOML:: End common
* Gould:: non-base register symbols used on Gould systems
* N_LENG:: Length of preceding entry
@end menu
@ -3661,30 +3674,6 @@ Value is its address.
Modula2 scope information (Sun linker)
<<?>>
@node N_BCOMM
@section 226 - 0xe2 - N_BCOMM
Begin named common block.
Only the name is significant.
<<?>>
@node N_ECOMM
@section 228 - 0xe4 - N_ECOMM
End named common block.
Only the name is significant and it should match the N_BCOMM
<<?>>
@node N_ECOML
@section 232 - 0xe8 - N_ECOML
End common (local name)
value is address.
<<?>>
@node Gould
@section Non-base registers on Gould systems
@ -3855,7 +3844,7 @@ new type defined in the compilation. GNU C stabs use the type number
alone, with no source file number.
@end itemize
@node stabs-in-elf
@node Stabs-in-elf
@appendix Using stabs with the ELF object file format.
The ELF object file format allows tools to create object files with custom