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

[Nick Desaulniers via libc-commits]

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@@ -0,0 +1,49 @@
+//===-- 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)) {
+  // TODO (https://github.com/llvm/llvm-project/issues/115907): invoke
+  // constraint handler
+  if (buffer == nullptr || t_ptr == nullptr)
+    return EINVAL;
+
+  if (*t_ptr > cpp::numeric_limits<int32_t>::max()) {
+    if (buffer_size != 0 && buffer_size <= RSIZE_MAX)
----------------
nickdesaulniers wrote:

FWIW, I looked up more details about "what is a constraint violation?"

K.3.4.2:
>  Functions that have parameters of type rsize_t consider it a runtime-constraint violation if the values of those parameters are greater than RSIZE_MAX.

So the setting of buffer[0] to 0 only needs to occur for the rsize bounds check, not the time numerics limits check.  Caveat being if I understood the standard correctly.

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