GCC routinely puts on the fly type description in other stabs. For
example,
0000006c - 00 0002 PSYM argv:p(0,2)=*(0,3)=*(0,4)=r(0,4);0;127;
Now when this PSYM stab is discarded by linker the useful type info
is lost. This happens a lot in -feliminate-unused-debug-symbols mode.
It happens even more in GCC-4.0 compared to GCC-3.3. Plus it is
useful to put avoid on the fly type descriptions for the Essential
Symbols work done here at Apple. And one small thing, it is less
confusing to GDB when type is described first before being used. (And
that is in -feliminate-unused-debug-symbols mode :)). So instead of
generating these stabs
00000000 - 01 0003 FUN main:F(0,1)
00000000 - 00 0000 LSYM int:t(0,1)=r(0,1);-2147483648;2147483647;
00000068 - 00 0002 PSYM argc:p(0,1)
0000006c - 00 0002 PSYM argv:p(0,2)=*(0,3)=*(0,4)
00000000 - 00 0000 LSYM char:t(0,4)=r(0,4);0;127;
0000004c - 00 0000 FUN
It is desirable that GCC produces this
00000000 - 01 0003 FUN main:F(0,1)
00000068 - 00 0002 PSYM argc:p(0,1)
0000006c - 00 0002 PSYM argv:p(0,2)
00000000 - 00 0000 LSYM int:t(0,1)=r(0,1);-2147483648;2147483647;
00000000 - 00 0000 LSYM :t(0,2)=*(0,3)
00000000 - 00 0000 LSYM :t(0,3)=*(0,4)
00000000 - 00 0000 LSYM char:t(0,4)=r(0,4);0;127;
0000004c - 00 0000 FUN
I've now patch ready (based on apple-local-200502-branch) but it
requires few bug fixes in darwin GDB. My simple question is : Is
anybody interested in reviewing this GCC patch for acceptance in FSF
GCC (4.1 or 4.2 or whenever) irrespective of whether associated GDB
changes are contributed or not? Apple linker is updated to avoid 't'
and 'T' LSYM stabs while removing chunks of stabs. I am not sure how
big deal it is for FSF linker. And I do not know whether these linker
changes will find its way in FSF linker or not.
I know, this is about stabs and not many folks care about stabs. And
on top of that it is related to -feliminate-unused-debug-symbols mode
mainly. Plus issue of getting other tools on the same page. So I'd
like to understand the interest before sending patch (and later on
annoying ping messages :) ).
[ Do not say anything about switching to Dwarf. Other folks here at
Apple are working on it. ]
-
Devang
