[libc-commits] [libc] [libc][c23] add memset_explicit (PR #83577)

[Nick Desaulniers via libc-commits]

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@@ -0,0 +1,27 @@
+//===-- Implementation of memset_explicit ---------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/string/memset_explicit.h"
+#include "src/__support/common.h"
+#include "src/string/memory_utils/flush_cache.h"
+#include "src/string/memory_utils/inline_memset.h"
+
+namespace LIBC_NAMESPACE {
+
+[[gnu::noinline]] LLVM_LIBC_FUNCTION(void *, memset_explicit,
+                                     (void *dst, int value, size_t count)) {
+  // Use the inline memset function to set the memory.
+  inline_memset<true>(dst, static_cast<uint8_t>(value), count);
----------------
nickdesaulniers wrote:

Are we sure that inline_memset complies with the requirements of the standard?

[The part Jens' refers to](https://gustedt.gitlabpages.inria.fr/c23-library/#memset_explicit):

> To avoid side-channel attacks, the implementation of the function should make no explicit or implicit reference to the contents of the byte array nor the value that has been chosen for the overwrite. Each write operation should use the same time (and other resources) per byte.


https://github.com/llvm/llvm-project/pull/83577