foo.c:
asm (
".globl bar\n\t"
"bar:\n\t"
"movl $5, %eax\n\t"
"ret"
);
main() {
return bar();
}
$ gcc -g2 foo.c; ./a.out; echo $?
5
$ gcc foo.c -g3; ./a.out; echo $?
Segmentation fault
139
Disassembly of the a.out compiled with -g3 gives:
(gdb) disass main
Dump of assembler code for function main:
0x08048364 <main+0>: push %ebp
0x08048365 <main+1>: mov %esp,%ebp
0x08048367 <main+3>: sub $0x8,%esp
0x0804836a <main+6>: and $0xfffffff0,%esp
0x0804836d <main+9>: mov $0x0,%eax
0x08048372 <main+14>: add $0xf,%eax
0x08048375 <main+17>: add $0xf,%eax
0x08048378 <main+20>: shr $0x4,%eax
0x0804837b <main+23>: shl $0x4,%eax
0x0804837e <main+26>: sub %eax,%esp
0x08048380 <main+28>: call 0x4852
0x08048385 <main+33>: leave
0x08048386 <main+34>: ret
End of assembler dump.
Note the call to an invalid location; it is this that causes the segfault.
Seen in the wild in tetex-3.0 (uses asm functions in metafont).
Workaround: don't use -g3.
I will attach gcc -g3 -S foo.c output.
--
Summary: -g3 (-ggdb3) emits broken calls to asm-defined functions
Product: gcc
Version: 3.4.6
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: ed at catmur dot co dot uk
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=26908
