[libc-commits] [libc] [libc] Add `ctime_s` (PR #110676)

[Nick Desaulniers via libc-commits]

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@@ -0,0 +1,43 @@
+//===-- Implementation of ctime_s function --------------------------------===//
+//
+// 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 "ctime_s.h"
+#include "hdr/errno_macros.h"
+#include "src/__support/CPP/limits.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "time_utils.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+using LIBC_NAMESPACE::time_utils::TimeConstants;
+
+LLVM_LIBC_FUNCTION(int, ctime_s,
+                   (char *buffer, rsize_t buffer_size, const time_t *t_ptr)) {
+  if (t_ptr == nullptr || buffer == nullptr ||
+      *t_ptr > cpp::numeric_limits<int32_t>::max()) {
+    if (buffer != nullptr)
+      buffer[0] = '\0';
+    return EINVAL;
+  }
+
+  if (buffer_size < TimeConstants::ASCTIME_MAX_BYTES) {
+    buffer[0] = '\0';
----------------
nickdesaulniers wrote:

For this case, I think we can `#include <stdint.h>` to get the compiler's definition of `RSIZE_MAX`. Looking at clang's internal stdint.h (clang/lib/Headers/stdint.h), `__STDC_WANT_LIB_EXT1__` must be defined to a value greater than or equal to 1 BEFORE including stdint.h to have access to the macro.

https://github.com/llvm/llvm-project/pull/110676