[libc] Add ctime_s

Resolves #110548

Definition:

```c++
int ctime_s(char *buffer, size_t buffer_size, const time_t *t_ptr);

```

Author: Rajveer100

libc/config/baremetal/arm/entrypoints.txt

@@ -205,6 +205,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.time.asctime_r
     libc.src.time.ctime
     libc.src.time.ctime_r
+    libc.src.time.ctime_s
     libc.src.time.difftime
     libc.src.time.gmtime
     libc.src.time.gmtime_r

libc/config/baremetal/riscv/entrypoints.txt

@@ -201,6 +201,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.time.asctime_r
     libc.src.time.ctime
     libc.src.time.ctime_r
+    libc.src.time.ctime_s
     libc.src.time.difftime
     libc.src.time.gmtime
     libc.src.time.gmtime_r

libc/config/linux/aarch64/entrypoints.txt

@@ -969,6 +969,7 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.time.asctime_r
     libc.src.time.ctime
     libc.src.time.ctime_r
+    libc.src.time.ctime_s
     libc.src.time.clock
     libc.src.time.clock_gettime
     libc.src.time.difftime

libc/config/linux/riscv/entrypoints.txt

@@ -901,6 +901,7 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.time.asctime_r
     libc.src.time.ctime
     libc.src.time.ctime_r
+    libc.src.time.ctime_s
     libc.src.time.clock
     libc.src.time.clock_gettime
     libc.src.time.difftime

libc/config/linux/x86_64/entrypoints.txt

@@ -1026,6 +1026,7 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.time.asctime_r
     libc.src.time.ctime
     libc.src.time.ctime_r
+    libc.src.time.ctime_s
     libc.src.time.clock
     libc.src.time.clock_gettime
     libc.src.time.difftime

libc/docs/date_and_time.rst

@@ -59,6 +59,8 @@ Implementation Status
 +---------------------+---------+---------+---------+-----------------+---------+---------+---------+---------+---------+---------+---------+---------+
 | ctime_r             | |check| | |check| |         |     |check|     |         |         |         |         |         |         |         |         |
 +---------------------+---------+---------+---------+-----------------+---------+---------+---------+---------+---------+---------+---------+---------+
+| ctime_s             | |check| | |check| |         |     |check|     |         |         |         |         |         |         |         |         |
++---------------------+---------+---------+---------+-----------------+---------+---------+---------+---------+---------+---------+---------+---------+
 | clock               | |check| | |check| |         |     |check|     |         |         |         |         |         |         |         |         |
 +---------------------+---------+---------+---------+-----------------+---------+---------+---------+---------+---------+---------+---------+---------+
 | clock_getcpuclockid |         |         |         |                 |         |         |         |         |         |         |         |         |

libc/newhdrgen/yaml/time.yaml

@@ -37,6 +37,14 @@ functions:
     arguments:
       - type: const time_t *
       - type: char *
+  - name: ctime_s
+    standard:
+      - stdc
+    return_type: int
+    arguments:
+      - type: char *
+      - type: size_t
+      - type: const time_t *
   - name: clock
     standard:
       - stdc

libc/spec/stdc.td

@@ -1630,6 +1630,15 @@ def StdC : StandardSpec<"stdc"> {
                   ArgSpec<CharPtr>,
               ]
           >,
+          FunctionSpec<
+              "ctime_s",
+              RetValSpec<IntType>,
+              [
+                  ArgSpec<CharPtr>,
+                  ArgSpec<SizeTType>,
+                  ArgSpec<ConstTimeTTypePtr>,
+              ]
+          >,
           FunctionSpec<
               "clock",
               RetValSpec<ClockT>,

libc/src/time/CMakeLists.txt

@@ -60,6 +60,18 @@ add_entrypoint_object(
     libc.include.time
 )
 
+add_entrypoint_object(
+  ctime_s
+  SRCS
+    ctime_s.cpp
+  HDRS
+    ctime_s.h
+  DEPENDS
+    .time_utils
+    libc.hdr.types.time_t
+    libc.include.time
+)
+
 add_entrypoint_object(
   difftime
   SRCS

libc/src/time/ctime_s.cpp

@@ -0,0 +1,39 @@
+//===-- 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, size_t buffer_size, const time_t *t_ptr)) {
+  if (t_ptr == nullptr || buffer == nullptr ||
+      *t_ptr > cpp::numeric_limits<int32_t>::max()) {
+    return EINVAL;
+  }
+
+  if (buffer_size < TimeConstants::ASCTIME_MAX_BYTES) {
+    return ERANGE;
+  }
+
+  if (time_utils::asctime(time_utils::localtime(t_ptr), buffer, buffer_size) ==
+      nullptr) {
+    return EINVAL;
+  }
+
+  return 0;
+}
+
+} // namespace LIBC_NAMESPACE_DECL