From f0c1dedf0df71b4029d9b0ce8ba19d8af2a60af5 Mon Sep 17 00:00:00 2001 From: Andreas Jaeger Date: Thu, 3 May 2012 22:12:59 +0200 Subject: Fix tst-obprintf - and mcheck in general 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). --- malloc/mcheck.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'malloc') diff --git a/malloc/mcheck.c b/malloc/mcheck.c index 9213740360..9d8a414676 100644 --- a/malloc/mcheck.c +++ b/malloc/mcheck.c @@ -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; -- cgit 1.4.1