Zero offheap on commit on OSX

For some reason OSX does not seem to zero memory on commit, unless it's
the first commit. For now, till we understand if there is a way to force
zero on subsequent re-commits, we will zero it explicitly.

Including zPTF as well, since we don't know how it will behave, even
if/when it adds support for commit/decommit/virtual-memory.

Signed-off-by: Aleksandar Micic <[email protected]>

gc/base/SparseVirtualMemory.cpp

@@ -132,6 +132,11 @@ MM_SparseVirtualMemory::allocateSparseFreeEntryAndMapToHeapObject(void *proxyObj
 	void *sparseHeapAddr = _sparseDataPool->findFreeListEntry(adjustedSize);
 	bool success = MM_VirtualMemory::commitMemory(sparseHeapAddr, adjustedSize);
 
+#if defined(OSX) || defined(OMRZTPF)
+	/* Most platforms will perform an implicit zero through the preceding commit. */
+	OMRZeroMemory(sparseHeapAddr, adjustedSize);
+#endif /* defined(OSX) || defined(OMRZTPF)) */
+
 	if (NULL != sparseHeapAddr) {
 		_sparseDataPool->mapSparseDataPtrToHeapProxyObjectPtr(sparseHeapAddr, proxyObjPtr, adjustedSize);
 	} else {