http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49888
Summary: VTA: -O2 -g variable value changes, it does not change
in the source
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: jan.kratoch...@redhat.com
CC: aol...@gcc.gnu.org
Target: x86_64-unknown-linux-gnu
static int v;
static void __attribute__((noinline, noclone))
f (int *p)
{
int c = *p;
v = c;
*p = 2;
v = 0; /* break-here */
}
int
main ()
{
int v = 2;
f (&v);
return 0;
}
--------------------------------------------------------------------------------
FAIL: gcc (GCC) 4.5.4 20110728 (prerelease)
FAIL: gcc (GCC) 4.6.2 20110728 (prerelease)
FAIL: gcc (GCC) 4.7.0 20110728 (experimental)
-Wall -g -O2
--------------------------------------------------------------------------------
Breakpoint 1, f (p=0x7fffffffda44) at 8.c:7
7 *p = 2;
(gdb) disass
Dump of assembler code for function f:
=> 0x0000000000400480 <+0>: movl $0x2,(%rdi)
0x0000000000400486 <+6>: movl $0x0,0x2003e8(%rip) # 0x600878 <v>
0x0000000000400490 <+16>: retq
End of assembler dump.
(gdb) p c
$1 = 1
(gdb) stepi
8 v = 0; /* break-here */
(gdb) p c
Actual:
$2 = 2
Expected:
$2 = 1
`c' is never changed in the source code, it should not change in runtime.
<63> DW_AT_location : 2 byte block: 75 0 (DW_OP_breg5 (rdi): 0)
<optimized out> would be better than a wrong value.
