consolidate fork detection prelude

CMakeLists.txt

@@ -311,7 +311,7 @@ function(feature_probe PROBE_NAME)
         SOURCES "${CMAKE_CURRENT_LIST_DIR}/tests/features/${PROBE_NAME}.c"
         LINK_LIBRARIES ${LINK_LIB} ${OS_LIBS}
         CMAKE_FLAGS ${ADDITIONAL_FLAGS}
-        COMPILE_DEFINITIONS -include "${CMAKE_CURRENT_LIST_DIR}/utils/s2n_prelude.h" -c ${GLOBAL_FLAGS} ${PROBE_FLAGS}
+        COMPILE_DEFINITIONS -I "${CMAKE_CURRENT_LIST_DIR}" -include "${CMAKE_CURRENT_LIST_DIR}/utils/s2n_prelude.h" -c ${GLOBAL_FLAGS} ${PROBE_FLAGS}
         ${ARGN}
         OUTPUT_VARIABLE TRY_COMPILE_OUTPUT
     )

tests/features/S2N_MADVISE_SUPPORTED.c

@@ -13,17 +13,7 @@
  * permissions and limitations under the License.
  */
 
-/* Keep in sync with utils/s2n_fork_detection.c */
-#if defined(__FreeBSD__)
-    /* FreeBSD requires POSIX compatibility off for its syscalls (enables __BSD_VISIBLE)
-     * Without the below line, <sys/mman.h> cannot be imported (it requires __BSD_VISIBLE) */
-    #undef _POSIX_C_SOURCE
-#elif !defined(__APPLE__) && !defined(_GNU_SOURCE)
-    #define _GNU_SOURCE
-#endif
-
-#include <stddef.h>
-#include <sys/mman.h>
+#include "utils/s2n_fork_detection_prelude.h"
 
 int main() {
     madvise(NULL, 0, 0);

tests/features/S2N_MINHERIT_SUPPORTED.c

@@ -13,15 +13,7 @@
  * permissions and limitations under the License.
  */
 
-/* Keep in sync with utils/s2n_fork_detection.c */
-#if defined(__FreeBSD__)
-    /* FreeBSD requires POSIX compatibility off for its syscalls (enables __BSD_VISIBLE)
-     * Without the below line, <sys/mman.h> cannot be imported (it requires __BSD_VISIBLE) */
-    #undef _POSIX_C_SOURCE
-#endif
-
-#include <stddef.h>
-#include <sys/mman.h>
+#include "utils/s2n_fork_detection_prelude.h"
 
 int main() {
     minherit(NULL, 0, 0);

utils/s2n_fork_detection.c

@@ -13,33 +13,7 @@
  * permissions and limitations under the License.
  */
 
-/* This captures Darwin specialities. This is the only APPLE flavor we care about.
- * Here we also capture varius required feature test macros.
- */
-#if defined(__APPLE__)
-typedef struct _opaque_pthread_once_t __darwin_pthread_once_t;
-typedef __darwin_pthread_once_t pthread_once_t;
-    #define _DARWIN_C_SOURCE
-#elif defined(__FreeBSD__) || defined(__OpenBSD__)
-    /* FreeBSD requires POSIX compatibility off for its syscalls (enables __BSD_VISIBLE)
-     * Without the below line, <sys/mman.h> cannot be imported (it requires __BSD_VISIBLE) */
-    #undef _POSIX_C_SOURCE
-#elif !defined(_GNU_SOURCE)
-    /* Keep in sync with feature probe tests/features/madvise.c */
-    #define _GNU_SOURCE
-#endif
-
-#include <sys/mman.h>
-
-/* Not always defined for Darwin */
-#if !defined(MAP_ANONYMOUS)
-    #define MAP_ANONYMOUS MAP_ANON
-#endif
-
-#include <pthread.h>
-#include <stdlib.h>
-#include <sys/types.h>
-#include <unistd.h>
+#include "utils/s2n_fork_detection_prelude.h"
 
 #include "error/s2n_errno.h"
 #include "utils/s2n_fork_detection.h"

utils/s2n_fork_detection_prelude.h

@@ -0,0 +1,41 @@
+/*
+ * 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.
+ */
+
+/* This captures Darwin specialities. This is the only APPLE flavor we care about.
+ * Here we also capture varius required feature test macros.
+ */
+#if defined(__APPLE__)
+typedef struct _opaque_pthread_once_t __darwin_pthread_once_t;
+typedef __darwin_pthread_once_t pthread_once_t;
+    #define _DARWIN_C_SOURCE
+#elif defined(__FreeBSD__) || defined(__OpenBSD__)
+    /* FreeBSD requires POSIX compatibility off for its syscalls (enables __BSD_VISIBLE)
+     * Without the below line, <sys/mman.h> cannot be imported (it requires __BSD_VISIBLE) */
+    #undef _POSIX_C_SOURCE
+#elif !defined(_GNU_SOURCE)
+    #define _GNU_SOURCE
+#endif
+
+#include <sys/mman.h>
+
+/* Not always defined for Darwin */
+#if !defined(MAP_ANONYMOUS)
+    #define MAP_ANONYMOUS MAP_ANON
+#endif
+
+#include <pthread.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <unistd.h>