Re: Get longjmp target check in breakpoint.c - is it necessary?

[Sergio Durigan Junior <sergiodj at redhat dot com>]

On Thursday, October 31 2013, Edjunior Barbosa Machado wrote:

> Hi Tiago,

Hey :-)

> On 10/31/2013 12:36 AM, Tiago StÃrmer Daitx wrote:
>> We have in gdb/breakpoint.c the following condition checking:
>> 
>>  3222       if (!gdbarch_get_longjmp_target_p (gdbarch))Â
>>  3223 Â       continue;Â
>> 
>> Which is forcing me to implement an (unnecessary?) arch specific
>> get_longjmp_target while having a longjmp user probe in glibc should be
>> enough. Removing that if/continue statement showed no regressions - it
>> actually fixed 3 longjmp failures (assuming proper support in glibc for
>> a longjmp probe is in place). 
>
> If I understood correctly, there are different longjmps symbols search
> strategies on this create_longjmp_master_breakpoint() function: the
> recent libc probe search and the per-objfile cache lookup.
>
> It seems this 'if' works like an optimization to avoid searching for
> symbols if the arch didn't provide support for get_longjmp_target().
> However, <arch>_get_longjmp_target() function became unnecessary in
> targets that provide libc probe support, as you noticed with the
> addition of probes on ppc64 glibc.
>
> What if you try to move this 'if' to a bit below in the function (right
> before "for (i = 0; i < NUM_LONGJMP_NAMES; i++)" loop)?

Edjunior is right, Tiago.  This is a bug, actually.  This check should
be moved to the place Edjunior mentioned.  Could you post a patch to fix
that?

Thanks a lot for looking into this :-).

-- 
Sergio