[MPlayer-dev-eng] mplayer -pie and libbluray

[Reimar Döffinger]

On Wed, Aug 15, 2012 at 09:36:59PM +0200, Alexander Roalter wrote:
> On 08/15/2012 09:29 PM, Reimar Döffinger wrote:
> >On Wed, Aug 15, 2012 at 08:54:45PM +0200, Alexander Roalter wrote:
> >>On 08/15/2012 08:27 PM, Reimar Döffinger wrote:
> >>>
> >>>Yes, I tried playing a bluray, with both br:// and bd:// just to be sure.
> >>>I can't know for sure it hit the code-path that caused your issue.
> >>>Something like a backtrace of the crash and/or strdup and what the
> >>>pointer value looks like or so might help.
> >>>Maybe some kind of minimal reproduction case, like
> >>>char *a(void){ return strdup("test") };
> >>>compiled to a .so and a normal program compiled as PIE linking
> >>>against it to see if that also triggers the issue?
> >>>Or maybe figure out how address randomization is configured on your
> >>>system? Maybe changing that will determine if there is a problem or not?
> >>>However I can't really understand why it would work in valgrind,
> >>>except that I'd guess it ends up not using address randomization.
> >>
> >>I can make a small test app and a test.so, and both do strdup. It
> >>works even if I use PIE linking.
> >>
> >>But if I do add bd_open("/mnt/bd", NULL); and link against
> >>libbluray, then also the test application segfaults (with PIE) or
> >>works OK (without PIE).
> >>
> >>Running gdb on it... the bdpath=0xffffffff8201980 is an additional
> >>printf I inserted to see the %p of the strdup'ed string.
> >
> >Let me guess: they forgot to include string.h where that strdup is,
> >thus the return value is treated as int and sign-extended.
> >It just happens to work if all addresses are < 32.
> 
> On one hand you're right:
> 
> libbluray/bluray.c:1008:13: warning: implicit declaration of
> function ‘strdup’
> 
> But string.h is included, but only if one of the following is
> defined: __USE_SVID, __USE_BSD or __USE_XOPEN_EXTENDED

Oh, do you have some ancient libc?
strdup is supposed to be defined also if _POSIX_C_SOURCE >= 200809L,
which is probably what they are using. On the other hand, that's also
what MPlayer uses, so MPlayer shouldn't compile for you if that was
the issue...