FAIL: gcc (GCC) 4.5.0 20100202 (experimental)
FAIL: gcc-4.4.3-4.fc12.x86_64
<2><c2>: Abbrev Number: 8 (DW_TAG_variable)
<c3> DW_AT_name : x
<cb> DW_AT_location : 0x92 (location list)
00000092 0000000000400509 000000000040050f (DW_OP_reg0)
00000092 0000000000400510 0000000000400517 (DW_OP_lit0; DW_OP_stack_value)
00000092 <End of list>
40050b: e8 d8 fe ff ff callq 4003e8 <al...@plt>
400510: 31 c0 xor %eax,%eax
Why is "x" valid on 40050b, 40050c, 40050d, 40050e but optimized-out on 40050f?
:-)
Unfortunately GDB pretends exactly this PC-1 address at the caller frames.
DWARF3 Page 26:
2. An ending address offset. [...] It marks the first address past the end of
the address range over which the location is valid.
The bug is introduced by revision 151312 dwarf2out.c line:
sprintf (loclabel, "%s-1", last_label);
which causes:
(gdb) s
alarm () at ../sysdeps/unix/syscall-template.S:82
82 T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
(gdb) up
#1 0x0000000000400510 in main (argc=<value optimized out>, argv=<value
optimized out>)
at /home/jkratoch/t/zero.c:9
9 alarm (x);
(gdb) p/x $pc
$1 = 0x400510
(gdb) p x
$2 = <value optimized out>
after a fix:
sprintf (loclabel, "%s", last_label);
the loclist is now:
00000092 0000000000400509 0000000000400510 (DW_OP_reg0)
00000092 0000000000400510 0000000000400517 (DW_OP_lit0; DW_OP_stack_value)
00000092 <End of list>
and GDB prints:
(gdb) p x
$2 = 1804289383
Compiled this testcase with -Wall -g -O2; #includes were not inlined but I hope
it is not a problem for this Bug.
#include <stdlib.h>
#include <unistd.h>
int
main (int argc, char **argv)
{
int x = rand ();
alarm (x);
x = 0;
return x;
}
--
Summary: Location list ending address should not be one-less
Product: gcc
Version: 4.5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: jan dot kratochvil at redhat dot com
GCC target triplet: x86_64-unknown-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42939
