[Bug gdb/12257] gdb ignore line "bar: if(foo)goto bar;"

["tromey at redhat dot com" <sourceware-bugzilla@sourceware.org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=12257

Tom Tromey <tromey at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |tromey at redhat dot com
         Resolution|                            |INVALID

--- Comment #1 from Tom Tromey <tromey at redhat dot com> 2012-02-07 20:46:45 UTC ---
I think this is a gcc bug, not a gdb bug.

On Fedora 15,with the system gcc, it fails for me if I compile with -g.
But if I use -g -O1, it works

With plain -g, the line number table looks like:

CU: pr.c:
File name                            Line number    Starting address
pr.c                                           4            0x400534
pr.c                                           6            0x40053c
pr.c                                           7            0x40054e
pr.c                                           8            0x400569
pr.c                                           8            0x40056a
pr.c                                           9            0x400571
pr.c                                          10            0x400576

Note the address of the first occurrence of line 8.
Then if I disassemble I see:

        scanf("%d", &foo);
  40054e:       b8 84 06 40 00          mov    $0x400684,%eax
  400553:       48 8d 55 fc             lea    -0x4(%rbp),%rdx
  400557:       48 89 d6                mov    %rdx,%rsi
  40055a:       48 89 c7                mov    %rax,%rdi
  40055d:       b8 00 00 00 00          mov    $0x0,%eax
  400562:       e8 d1 fe ff ff          callq  400438 <__isoc99_scanf@plt>
  400567:       eb 01                   jmp    40056a <main+0x36>
bar:    if(foo)goto bar;
  400569:       90                      nop
  40056a:       8b 45 fc                mov    -0x4(%rbp),%eax
  40056d:       85 c0                   test   %eax,%eax
  40056f:       75 f8                   jne    400569 <main+0x35>
        return 0;

That is, the first "line 8" is that nop, which is skipped after the call.

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