From 9d1e6c8c8e1257195f99111bc4df8525c7cbabe8 Mon Sep 17 00:00:00 2001
From: Cameron Bytheway <bythewc@amazon.com>
Date: Tue, 19 Sep 2023 16:00:44 -0600
Subject: [PATCH] build: use feature probes for CLOEXEC (#4206)

---
 tests/features/S2N_CLOEXEC_SUPPORTED.c        | 20 +++++++++++++++++
 tests/features/S2N_CLOEXEC_SUPPORTED.flags    |  1 +
 tests/features/S2N_CLOEXEC_XOPEN_SUPPORTED.c  | 22 +++++++++++++++++++
 .../S2N_CLOEXEC_XOPEN_SUPPORTED.flags         |  1 +
 utils/s2n_random.c                            |  8 +++++--
 5 files changed, 50 insertions(+), 2 deletions(-)
 create mode 100644 tests/features/S2N_CLOEXEC_SUPPORTED.c
 create mode 100644 tests/features/S2N_CLOEXEC_SUPPORTED.flags
 create mode 100644 tests/features/S2N_CLOEXEC_XOPEN_SUPPORTED.c
 create mode 100644 tests/features/S2N_CLOEXEC_XOPEN_SUPPORTED.flags

diff --git a/tests/features/S2N_CLOEXEC_SUPPORTED.c b/tests/features/S2N_CLOEXEC_SUPPORTED.c
new file mode 100644
index 00000000000..2e6e7d003b1
--- /dev/null
+++ b/tests/features/S2N_CLOEXEC_SUPPORTED.c
@@ -0,0 +1,20 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+#include <fcntl.h>
+
+int main() {
+    return O_CLOEXEC;
+}
diff --git a/tests/features/S2N_CLOEXEC_SUPPORTED.flags b/tests/features/S2N_CLOEXEC_SUPPORTED.flags
new file mode 100644
index 00000000000..2f41be663b2
--- /dev/null
+++ b/tests/features/S2N_CLOEXEC_SUPPORTED.flags
@@ -0,0 +1 @@
+-Werror
diff --git a/tests/features/S2N_CLOEXEC_XOPEN_SUPPORTED.c b/tests/features/S2N_CLOEXEC_XOPEN_SUPPORTED.c
new file mode 100644
index 00000000000..ed2b748d8e5
--- /dev/null
+++ b/tests/features/S2N_CLOEXEC_XOPEN_SUPPORTED.c
@@ -0,0 +1,22 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+#define _XOPEN_SOURCE 700
+#include <fcntl.h>
+#undef _XOPEN_SOURCE
+
+int main() {
+    return O_CLOEXEC;
+}
diff --git a/tests/features/S2N_CLOEXEC_XOPEN_SUPPORTED.flags b/tests/features/S2N_CLOEXEC_XOPEN_SUPPORTED.flags
new file mode 100644
index 00000000000..2f41be663b2
--- /dev/null
+++ b/tests/features/S2N_CLOEXEC_XOPEN_SUPPORTED.flags
@@ -0,0 +1 @@
+-Werror
diff --git a/utils/s2n_random.c b/utils/s2n_random.c
index 485229dfdcf..6fc3d27ad72 100644
--- a/utils/s2n_random.c
+++ b/utils/s2n_random.c
@@ -28,13 +28,17 @@
  * 700.  In glibc 2.11 and earlier, one obtains the definitions by
  * defining _GNU_SOURCE.
  *
- * # Relavent Links
+ * We use two feature probes to detect the need to perform this workaround.
+ * It is only applied if we can't get CLOEXEC without it and the build doesn't
+ * fail with _XOPEN_SOURCE being defined.
+ *
+ * # Relevent Links
  *
  * - POSIX.1-2017: https://pubs.opengroup.org/onlinepubs/9699919799
  * - https://stackoverflow.com/a/5724485
  * - https://stackoverflow.com/a/5583764
  */
-#ifndef _XOPEN_SOURCE
+#if !defined(S2N_CLOEXEC_SUPPORTED) && defined(S2N_CLOEXEC_XOPEN_SUPPORTED) && !defined(_XOPEN_SOURCE)
     #define _XOPEN_SOURCE 700
     #include <fcntl.h>
     #undef _XOPEN_SOURCE