util: move some raw memory functions from string-util.h → memory-util.h

src/basic/memory-util.c

@@ -37,3 +37,21 @@ bool memeqzero(const void *data, size_t length) {
         /* Now we know first 16 bytes are NUL, memcmp with self.  */
         return memcmp(data, p + i, length) == 0;
 }
+
+#if !HAVE_EXPLICIT_BZERO
+/*
+ * The pointer to memset() is volatile so that compiler must de-reference the pointer and can't assume that
+ * it points to any function in particular (such as memset(), which it then might further "optimize"). This
+ * approach is inspired by openssl's crypto/mem_clr.c.
+ */
+typedef void *(*memset_t)(void *,int,size_t);
+
+static volatile memset_t memset_func = memset;
+
+void* explicit_bzero_safe(void *p, size_t l) {
+        if (l > 0)
+                memset_func(p, '\0', l);
+
+        return p;
+}
+#endif