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From: Andreas Schwab <schwab@suse.de>
To: "Seong-Kook Shin" <cinsky@gmail.com>
Cc: gdb@sourceware.org
Subject: Re: signal 0 command
References: <991f3a0a0808210503y3c2c9218h5fcfb7bf544215da@mail.gmail.com>
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Date: Thu, 21 Aug 2008 21:25:00 -0000
In-Reply-To: <991f3a0a0808210503y3c2c9218h5fcfb7bf544215da@mail.gmail.com> 	(Seong-Kook Shin's message of "Thu, 21 Aug 2008 21:03:23 +0900")
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"Seong-Kook Shin" <cinsky@gmail.com> writes:

> If I understand correctly, I can issue "signal 0" to ignore the current
> signal GDB caught, right?  So I made a simple program to raise SIGSEGV:
>
> void
> foo(const char *str)
> {
>   char *p = 0;     /* This should be "char *p = str" */
>
>   while (*p != '\0') {
>     /* do something */
>     p++;
>   }
> }
>
> After reading the manual, I thought that it is possible to
> undo the generation of SIGSEGV after modifying the value `p'.
> But when I set the value of `p' corrently, and execute "signal 0",
> I can still see the SIGSEGV is generated.

Modifying the variable does not necessarily mean that the current
instruction can see the change.  The value may be been loaded into a
register which is used instead by the insn.  You may have to modify the
program counter to move back to where the variable's value is loaded.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
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"And now for something completely different."