Re: pfunct crash on libSDL

[Arnaldo Carvalho de Melo <acme-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

Em Mon, Nov 10, 2008 at 04:57:51PM +0100, Diego 'Flameeyes' Pettenò escreveu:
> Arnaldo Carvalho de Melo <acme-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> writes:
> 
> > Humm, I see, its the other file in this tarball, the one without
> > debugging info, that makes the CTF code crash in pfunct, I'll fix that,
> > but please use the file with .debug suffix for now, its there that the
> > DWARF info is anyway :-)
> 
> Ah okay :) I'm used to just run on the main binary, hoping that the
> debug link is followed, I guess I'll have to change my process, but then
> I'll be feature-requesting for the debuglink to be followed :P

I thought that libdwfl would do that, lemme check... Yeah:

open("tmp/usr/lib64/libSDL-1.2.so.0.11.2", O_RDONLY) = 3
open("tmp/usr/lib64/libSDL-1.2.so.0.11.2.debug", O_RDONLY) = -1 ENOENT (No such file or directory)
open("tmp/usr/lib64/.debug/libSDL-1.2.so.0.11.2.debug", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/home/acme/git/pahole/tmp/usr/lib64/libSDL-1.2.so.0.11.2.debug", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/home/acme/git/pahole/tmp/usr/lib64/.debug/libSDL-1.2.so.0.11.2.debug", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/lib/debug/home/acme/git/pahole/tmp/usr/lib64/libSDL-1.2.so.0.11.2.debug", O_RDONLY) = -1 ENOENT (No such file or directory)

So its just a matter of using one of the searched places :-)

To try this I just did a 'yum install SDL-debuginfo' and:

acme@doppio pahole]$ pfunct -TVIlf SDL_PauseAudio
/usr/lib64/libSDL-1.2.so.0
/* <1b92> src/audio/SDL_audio.c:589 */
void SDL_PauseAudio(int pause_on);
{ /* low_pc=0x88b0 */
	SDL_AudioDevice * audio;                                // 590
}/* size: 20, variables: 1 */
[acme@doppio pahole]$

So it works, but this time by using build id :-)

[acme@doppio pahole]$ strace -e trace=open pfunct -TVIlf SDL_PauseAudio /usr/lib64/libSDL-1.2.so.0 2>&1 | grep debug
open("/usr/lib/debug/.build-id/06/5ae7d6742b683430474e3415ae5081be5586a7.debug", O_RDONLY) = 3
[acme@doppio pahole]$

But...

[acme@doppio pahole]$ l
/usr/lib/debug/.build-id/06/5ae7d6742b683430474e3415ae5081be5586a7.debug lrwxrwxrwx 1 root root 42 2008-11-10 14:08
/usr/lib/debug/.build-id/06/5ae7d6742b683430474e3415ae5081be5586a7.debug -> ../../usr/lib64/libSDL-1.2.so.0.11.2.debug*
[acme@doppio pahole]$

Let us try removing this symlink... It still works, but this time:

[acme@doppio pahole]$ strace -e trace=open pfunct -TVIlf SDL_PauseAudio /usr/lib64/libSDL-1.2.so.0 2>&1 | grep debug
open("/usr/lib/debug/.build-id/06/5ae7d6742b683430474e3415ae5081be5586a7.debug", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/lib64/libSDL-1.2.so.0.11.2.debug", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/lib64/.debug/libSDL-1.2.so.0.11.2.debug", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/lib/debug/usr/lib64/libSDL-1.2.so.0.11.2.debug", O_RDONLY) = 3
[acme@doppio pahole]$

- Arnaldo
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