On Thu, Aug 16, 2012 at 12:06 PM, Richard Guenther
<richard.guent...@gmail.com> wrote:
> On Thu, Aug 16, 2012 at 1:11 AM, Steven Bosscher <stevenb....@gmail.com>
> wrote:
>> On Mon, Aug 6, 2012 at 1:27 PM, Paolo Bonzini <bonz...@gnu.org> wrote:
>>>> 2. sparseset has the same problem of memory clearing (for valgrind,
>>>> see sparseset_alloc).
>>>
>>> ... only the sparse array needs this clearing, but currently we do it
>>> for both.
>>
>> And according to the fat comment before the xcalloc, it's not even
>> really needed. Why can't we just tell valgrind to treat the memory as
>> defined, like in this patchlet:
>
> Indeed ... I suppose ok if it bootstraps / tests w/o valgrind checking and
> if a cc1 builds with valgrind checking.
Here's what I'll commit:
Index: sparseset.c
===================================================================
--- sparseset.c (revision 190474)
+++ sparseset.c (working copy)
@@ -30,12 +30,14 @@
unsigned int n_bytes = sizeof (struct sparseset_def)
+ ((n_elms - 1) * 2 * sizeof (SPARSESET_ELT_TYPE));
- /* We use xcalloc rather than xmalloc to silence some valgrind uninitialized
+ sparseset set = XNEWVAR(struct sparseset_def, n_bytes);
+
+ /* Mark the sparseset as defined to silence some valgrind uninitialized
read errors when accessing set->sparse[n] when "n" is not, and never has
been, in the set. These uninitialized reads are expected, by design and
- harmless. If this turns into a performance problem due to some future
- additional users of sparseset, we can revisit this decision. */
- sparseset set = (sparseset) xcalloc (1, n_bytes);
+ harmless. */
+ VALGRIND_DISCARD (VALGRIND_MAKE_MEM_DEFINED (set, n_bytes));
+
set->dense = &(set->elms[0]);
set->sparse = &(set->elms[n_elms]);
set->size = n_elms;
