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Fix tst-obprintf - and mcheck in general

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tst-obprintf failed with GCC 4.7.

It turned out that this is the fault of GCC optimizing away the
following from malloc/mcheck.c:
      /* We call malloc() once here to ensure it is initialized.  */
      void *p = malloc (0);
      free (p);

gcc sees the malloc(0);free pair and removes it completely.

And now malloc is not properly initialized and we screw up if both
mcheck is used (via tst-obprintf) and MALLOC_CHECK_ is set (as it is in my
environment).
This commit is contained in:
Andreas Jaeger 2012-05-03 22:12:59 +02:00
parent a65ef2aefa
commit f0c1dedf0d
2 changed files with 12 additions and 0 deletions
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6
ChangeLog
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@ -1,3 +1,9 @@
2012-05-03 Andreas Jaeger <aj@suse.de>
* malloc/mcheck.c (mcheck): Add barrier so that malloc/free pair
does not get optimized out.
(malloc_opt_barrier): New.
2012-05-03 Andreas Jaeger <aj@suse.de>
Roland McGrath <roland@hack.frob.com>

6
malloc/mcheck.c
View File

@ -370,6 +370,10 @@ mabort (enum mcheck_status status)
#endif
}
/* Memory barrier so that GCC does not optimize out the argument. */
#define malloc_opt_barrier(x) \
({ __typeof (x) __x = x; __asm ("" : "+m" (__x)); __x; })
int
mcheck (func)
void (*func) (enum mcheck_status);
@ -381,6 +385,8 @@ mcheck (func)
{
/* We call malloc() once here to ensure it is initialized. */
void *p = malloc (0);
/* GCC might optimize out the malloc/free pair without a barrier. */
p = malloc_opt_barrier (p);
free (p);
old_free_hook = __free_hook;