preserve zeroing on madvise out-of-memory error

Author: thestinger

pages.c

@@ -1,4 +1,5 @@
 #include <errno.h>
+#include <string.h>
 
 #include "memory.h"
 #include "pages.h"
@@ -83,6 +84,8 @@ void *allocate_pages_aligned(size_t usable_size, size_t alignment, size_t guard_
 
 void deallocate_pages(void *usable, size_t usable_size, size_t guard_size) {
     if (unlikely(memory_unmap((char *)usable - guard_size, usable_size + guard_size * 2))) {
-        memory_purge(usable, usable_size);
+        if (unlikely(memory_purge(usable, usable_size))) {
+            memset(usable, 0, usable_size);
+        }
     }
 }