[Bug 3919] New: crash in _longjmp_unwind (siglongjmp)

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=3919

           Summary: crash in _longjmp_unwind (siglongjmp)
           Product: uClibc
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P5
         Component: Other
        AssignedTo: unassigned at uclibc.org
        ReportedBy: busybox-bugzilla at plan9.de
                CC: uclibc-cvs at uclibc.org
   Estimated Hours: 0.0


with current builds, siglongjmp always jumps to 0 and crashes in static builds
without threads. reason is this test

  if (__pthread_cleanup_upto != NULL)

which is always true even, even if the function address is 0.

fixing it in a similar way as
http://ue.tst.eu/9d0e9de564d5c343c524e9742a17d204.txt makes it work - i
verified with this version of jmp-unwind.c (there might be other occurences of
this bug):

/* Defeat compiler optimization which assumes function addresses are never NULL
*/
static int not_null_ptr(const void *p)
{
       const void *q;
       __asm__ (""
               : "=r" (q) /* output */
               : "0" (p) /* input */
       );
       return q != 0;
}

void _longjmp_unwind (jmp_buf env, int val);
void
_longjmp_unwind (jmp_buf env, int val)
{
#ifdef SHARED
  if (__libc_pthread_functions_init)
    PTHFCT_CALL (ptr___pthread_cleanup_upto, (env->__jmpbuf,
                                              CURRENT_STACK_FRAME));
#else
  if (not_null_ptr(__pthread_cleanup_upto))
    __pthread_cleanup_upto (env->__jmpbuf, CURRENT_STACK_FRAME);
#endif
}

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