On 7/14/07, H.J. Lu <[EMAIL PROTECTED]> wrote:
This patch
http://gcc.gnu.org/ml/gcc-patches/2007-07/msg00165.html
causes the regression:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32748
The only relevant change is
Index: gcc/fortran/trans-decl.c
===================================================================
--- gcc/fortran/trans-decl.c (revision 126214)
+++ gcc/fortran/trans-decl.c (working copy)
@@ -2276,6 +2276,7 @@ gfc_build_builtin_function_decls (void)
(PREFIX("internal_realloc")),
pvoid_type_node, 2, pvoid_type_node,
gfc_index_int_type_node);
+ DECL_IS_MALLOC (gfor_fndecl_internal_realloc) = 1;
gfor_fndecl_allocate =
gfc_build_library_function_decl (get_identifier (PREFIX("allocate")),
In calls.c, there are comments:
/* The return value from a malloc-like function can not alias
anything else. */
It looks like gcc assumes a functon marked with DECL_IS_MALLOC won't
return an address which can alias something else. But it isn't true
for realloc. Now, the qestions are
1. Can gcc make such an assumption?
No, it can't. The returned memory may alias the original memory.
2. Can realloc be marked as DECL_IS_MALLOC.
... with DECL_IS_MALLOC the following
int *p;
p = malloc (4);
*p = 0;
p = realloc (p, 4);
*p = 1;
will have VOPs that do not prevent re-ordering of the two stores.
BTW, glibc also marks realloc with __attribute_malloc__.
Which is wrong as well.
Richard.
