This is with GCC trunk r126556 (2007-07-11).
Note that the instruction at 0x08048388 means that the offset from
%esp to the CFA is not a constant, but the .debug_frame information
for 0x0804838e and beyond claims the CFA is a constant distance from
either %esp or %ebp.
The proper behavior would be for the CFI to place the CFA relative to
%ecx from 0x08048388 to the end of the function.
$ cat align.c
int main(int argc, char **argv)
{
sleep (1);
return argc;
}
$ ~/gcc/pub/bin/gcc -g align.c -o align
$ readelf -wfF align
The section .eh_frame contains:
00000000 ZERO terminator
The section .debug_frame contains:
00000000 00000010 ffffffff CIE "" cf=1 df=-4 ra=8
LOC CFA ra
00000000 r4+4 c-4
00000014 00000024 00000000 FDE cie=00000000 pc=08048384..080483b0
LOC CFA r3 r4 r5 ra
08048384 r4+4 u u u c-4
08048388 r1+0 u r1 u c-4
0804838e r4+4 u r1 u c-4
0804838f r4+8 u r1 c-8 c-4
08048391 r5+8 u r1 c-8 c-4
08048393 r5+8 c-12 c-16 c-8 c-4
$ gdb align
GNU gdb Red Hat Linux (6.5-15.fc6rh)
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This GDB was configured as "i386-redhat-linux-gnu"...Using host libthread_db
library "/lib/libthread_db.so.1".
(gdb) disass main
Dump of assembler code for function main:
0x08048384 <main+0>: lea 0x4(%esp),%ecx
0x08048388 <main+4>: and $0xfffffff0,%esp
0x0804838b <main+7>: pushl 0xfffffffc(%ecx)
0x0804838e <main+10>: push %ebp
0x0804838f <main+11>: mov %esp,%ebp
0x08048391 <main+13>: push %ebx
0x08048392 <main+14>: push %ecx
0x08048393 <main+15>: sub $0x10,%esp
0x08048396 <main+18>: mov %ecx,%ebx
0x08048398 <main+20>: movl $0x1,(%esp)
0x0804839f <main+27>: call 0x80482a0 <[EMAIL PROTECTED]>
0x080483a4 <main+32>: mov (%ebx),%eax
0x080483a6 <main+34>: add $0x10,%esp
0x080483a9 <main+37>: pop %ecx
0x080483aa <main+38>: pop %ebx
0x080483ab <main+39>: pop %ebp
0x080483ac <main+40>: lea 0xfffffffc(%ecx),%esp
0x080483af <main+43>: ret
End of assembler dump.
(gdb)
--
Summary: GCC generates incorrect DWARF CFI for SSE stack
alignment
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: jimb at codesourcery dot com
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32743
