Re: [PATCH] Recognize and skip interpreter_p initialization in selftest.exp

[Mark Kettenis <mark dot kettenis at xs4all dot nl>]

> From: Fred Fish <fnf@specifix.com>
> Date: Sun, 26 Feb 2006 14:11:48 -0500
> 
> On Sunday 26 February 2006 13:40, Daniel Jacobowitz wrote:
> > happen?  Could you please verify a couple of things for me: that we are
> > reasonably close to the beginning of the function, that the prologue
> > skipper hasn't gone too far, and that the instruction being executed
> > has actually got some relationship to line 241.
> 
> I'm not very familiar with x86 assembly so I'm probably not the best one
> to look closely at the code generated for captured_main.

The mov $0x1,%edi is probably initializing a local variable to 1.  It
is very unlikely that this instruction is part of line 241; it's much
more likely this is line 186 or 189.  I'd say, that GCC is generating
bogus line number information or GDB is interpreting that line number
information uncorrectly.  Either way, your "fix" is probably papering
over a real bug.

> Here is what I get when I run by hand and do a bunch of "next" commands:
> 
> (gdb) br captured_main
> Breakpoint 1 at 0x807c714: file /src/latest/trunk/src/gdb/gdb/main.c, line 241.
> (gdb) run
> Starting program: /links/build/latest/trunk/i686-pc-linux-gnu/gdb/gdb/gdb
> Breakpoint 1, captured_main (data=0xbfbb4734) at /src/latest/trunk/src/gdb/gdb/main.c:241
> 241       interpreter_p = xstrdup (context->interpreter_p);
> (gdb) next
> 120     {
> (gdb)
> 241       interpreter_p = xstrdup (context->interpreter_p);
> (gdb)
> 120     {
> (gdb)
> 123       char **argv = context->argv;
> (gdb)
> 122       int argc = context->argc;
> (gdb)
> 123       char **argv = context->argv;
> (gdb)
> 122       int argc = context->argc;
> (gdb)
> 165       long time_at_startup = get_run_time ();
> (gdb)
> 168       setlocale (LC_MESSAGES, "");
> (gdb)
> 165       long time_at_startup = get_run_time ();
> (gdb)
> 168       setlocale (LC_MESSAGES, "");
> (gdb)
> 171       setlocale (LC_CTYPE, "");
> (gdb)
> 173       bindtextdomain (PACKAGE, LOCALEDIR);
> (gdb)
> 174       textdomain (PACKAGE);
> (gdb)
> 177       lim_at_start = (char *) sbrk (0);
> (gdb)
> 187       cmdarg = (struct cmdarg *) xmalloc (cmdsize * sizeof (*cmdarg));
> (gdb)
> 177       lim_at_start = (char *) sbrk (0);
> (gdb)
> 
> 
> I suppose it's possible though that the code at 0x807c714 doesn't have anything to
> do with line 241:
> 
> (gdb) x/40i captured_main
> 0x807c710 <captured_main>:      push   %ebp
> 0x807c711 <captured_main+1>:    mov    %esp,%ebp
> 0x807c713 <captured_main+3>:    push   %edi
> 0x807c714 <captured_main+4>:    mov    $0x1,%edi
> 0x807c719 <captured_main+9>:    push   %esi
> 0x807c71a <captured_main+10>:   mov    $0x1,%esi
> 0x807c71f <captured_main+15>:   push   %ebx
> 0x807c720 <captured_main+16>:   sub    $0x11c,%esp
> 0x807c726 <captured_main+22>:   mov    0x8(%ebp),%ebx
> 0x807c729 <captured_main+25>:   mov    0x4(%ebx),%edx
> 0x807c72c <captured_main+28>:   mov    (%ebx),%eax
> 0x807c72e <captured_main+30>:   mov    %edx,0xffffff08(%ebp)
> 0x807c734 <captured_main+36>:   mov    %eax,0xffffff04(%ebp)
> 0x807c73a <captured_main+42>:   call   0x8230970 <get_run_time>
> 0x807c73f <captured_main+47>:   movl   $0x823b767,0x4(%esp)
> 0x807c747 <captured_main+55>:   movl   $0x5,(%esp)
> 0x807c74e <captured_main+62>:   mov    %eax,0xffffff30(%ebp)
> 0x807c754 <captured_main+68>:   call   0x807ba20 <setlocale@plt>
> 0x807c759 <captured_main+73>:   movl   $0x823b767,0x4(%esp)
> 0x807c761 <captured_main+81>:   movl   $0x0,(%esp)
> 0x807c768 <captured_main+88>:   call   0x807ba20 <setlocale@plt>
> 0x807c76d <captured_main+93>:   movl   $0x8232b80,0x4(%esp)
> 0x807c775 <captured_main+101>:  movl   $0x8232a90,(%esp)
> 0x807c77c <captured_main+108>:  call   0x807bd20 <bindtextdomain@plt>
> 0x807c781 <captured_main+113>:  movl   $0x8232a90,(%esp)
> 0x807c788 <captured_main+120>:  call   0x807c030 <textdomain@plt>
> 0x807c78d <captured_main+125>:  movl   $0x0,(%esp)
> 0x807c794 <captured_main+132>:  call   0x807be10 <sbrk@plt>
> 0x807c799 <captured_main+137>:  movl   $0x8,(%esp)
> 0x807c7a0 <captured_main+144>:  mov    %eax,0x82d36e0
> 0x807c7a5 <captured_main+149>:  call   0x8084f20 <xmalloc>
> 0x807c7aa <captured_main+154>:  movl   $0x4,(%esp)
> 0x807c7b1 <captured_main+161>:  mov    %eax,0xffffff20(%ebp)
> 0x807c7b7 <captured_main+167>:  call   0x8084f20 <xmalloc>
> 0x807c7bc <captured_main+172>:  movl   $0x0,0x82d3b90
> 0x807c7c6 <captured_main+182>:  mov    %eax,0xffffff28(%ebp)
> 0x807c7cc <captured_main+188>:  mov    0x82b0d68,%eax
> 0x807c7d1 <captured_main+193>:  mov    %eax,(%esp)
> 0x807c7d4 <captured_main+196>:  call   0x8084f20 <xmalloc>
> 0x807c7d9 <captured_main+201>:  mov    %eax,0x82d36fc
>