[libc] add strerror_r function

I've implemente the gnu variant of strerror_r since that seems to be the
one more relevant to what we're trying to do.

Differential Revision: https://reviews.llvm.org/D135227

1 files changed, 23 insertions, 0 deletions

diff --git a/libc/src/string/strerror_r.cpp b/libc/src/string/strerror_r.cpp
new file mode 100644
index 000000000000..30147152c448
--- /dev/null
+++ b/libc/src/string/strerror_r.cpp
@@ -0,0 +1,23 @@
+//===-- Implementation of strerror_r --------------------------------------===//
+//
+// 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/strerror_r.h"
+#include "src/__support/common.h"
+#include "src/__support/error_to_string.h"
+
+#include <stddef.h>
+
+namespace __llvm_libc {
+
+// This is the gnu version of strerror_r. The XSI version may be added later.
+LLVM_LIBC_FUNCTION(char *, strerror_r,
+                   (int err_num, char *buf, size_t buflen)) {
+  return const_cast<char *>(get_error_string(err_num, {buf, buflen}).data());
+}
+
+} // namespace __llvm_libc