[Bug rtl-optimization/33796] valgrind error with -O2 for linux kernel code

["bonzini at gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #8 from bonzini at gnu dot org  2007-10-31 13:21 -------
Reopening and marking as enhancement.

A patch like this should work:

Index: sparseset.c
===================================================================
--- sparseset.c (revision 129768)
+++ sparseset.c (working copy)
@@ -21,6 +21,18 @@ along with GCC; see the file COPYING3.  
 #include "libiberty.h"
 #include "sparseset.h"

+#ifdef ENABLE_VALGRIND_CHECKING
+# ifdef HAVE_VALGRIND_MEMCHECK_H
+#  include <valgrind/memcheck.h>
+# elif defined HAVE_MEMCHECK_H
+#  include <memcheck.h>
+# else
+#  include <valgrind.h>
+# endif
+#else
+/* Avoid #ifdef:s when we can help it.  */
+#define VALGRIND_MAKE_MEM_DEFINED_IF_ADDRESSABLE(x, y)
+#endif

 /* Allocate and clear a n_elms SparseSet.  */

@@ -33,6 +45,8 @@ sparseset_alloc (SPARSESET_ELT_TYPE n_el
   sparseset set = (sparseset) xmalloc (n_bytes);
   set->dense = &(set->elms[0]);
   set->sparse = &(set->elms[n_elms]);
+  VALGRIND_MAKE_MEM_DEFINED_IF_ADDRESSABLE
+    (set->sparse, n_elms * sizeof (SPARSESET_ELT_TYPE));
   set->size = n_elms;
   sparseset_clear (set);
   return set;

but only if the compiler is compiled with --enable-checking=valgrind or
--enable-checking=yes,valgrind.  There are data structures that *rely* on safe
uninitialized data reads for speed, this is one of them.


-- 

bonzini at gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
             Status|RESOLVED                    |REOPENED
 GCC target triplet|x86_64-linux-gnu            |{i86,x86_64}-linux-gnu
         Resolution|INVALID                     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33796