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Re: gcc HEAD moves line number directives -- gcc bug?
- From: Daniel Jacobowitz <drow at mvista dot com>
- To: gdb at sources dot redhat dot com
- Date: Mon, 1 Sep 2003 20:39:53 -0400
- Subject: Re: gcc HEAD moves line number directives -- gcc bug?
- References: <200309011713.h81HDtHx003770@duracef.shout.net>
On Mon, Sep 01, 2003 at 01:13:55PM -0400, Michael Elizabeth Chastain wrote:
> Look at the code near 'call foo'. In gcc 3.3.1, the .loc lines
> match the source code. In gcc HEAD, the .loc line for line 24
> has migrated.
>
> Source code:
>
> /* 23 */ foo ();
> /* 24 */ a += 2;
>
> gcc 3.3.1 output:
>
> .loc 1 23 0
> call foo
> .loc 1 24 0
> leal -4(%ebp), %eax
> addl $2, (%eax)
>
> gcc HEAD output:
>
> .loc 1 23 0
> call foo
> leal -4(%ebp), %eax // this insn is part of line 24
> .loc 1 24 0 // this moved!
> addl $2, (%eax)
>
> This happens with explicit "-O0" in the command line.
>
> This causes some mild confusion with gdb. Specifically, an 'until'
> command on foo returns and says it is on line 24 with gcc 3.3.1,
> but on line 23 with gcc HEAD.
>
> I isolated the patch that caused this:
>
> http://gcc.gnu.org/ml/gcc-patches/2003-06/msg00430.html
> Jan Hubicka - Line number handling in RTL reorganization
>
> Do you think this is a bug in gcc? I do, but I need to check here
> before filing a bug report with gcc.
Maybe, maybe not... our testsuite certainly must accept returning to
both line 23 and 24. There are a number of architecures where a
function call includes instructions after the return (stack adjustment,
$gp reload...).
Line 24 is the addl. The leal is generated probably in reload; it's
not really part of any line, even though it was generated for line 24.
--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer