libreboot-utils: don't use the GNU SOURCE macro

use the POSIX one

declare prototypes where necessary.

Signed-off-by: Leah Rowe <leah@libreboot.org>

util/libreboot-utils/include/common.h

@@ -50,6 +50,12 @@
  */
 
 int fchmod(int fd, mode_t mode);
+char *realpath(const char *path,
+    char *resolved);
+
+#ifndef USE_URANDOM
+#define USE_URANDOM 0
+#endif
 
 #define MKHTEMP_RETRY_MAX 512
 #define MKHTEMP_SPIN_THRESHOLD 32

util/libreboot-utils/lib/file.c

@@ -16,8 +16,8 @@ more correct usage example:
 long max = pathconf("/", _PC_PATH_MAX);
  */
 
-#ifndef _GNU_SOURCE
+#ifndef _POSIX_C_SOURCE
-#define _GNU_SOURCE 1
+#define _POSIX_C_SOURCE 200809L
 #endif
 
 #include <sys/types.h>
@@ -34,6 +34,7 @@ long max = pathconf("/", _PC_PATH_MAX);
 #ifdef __linux__
 #include <linux/openat2.h>
 #include <sys/syscall.h>
+long syscall(long number, ...);
 #endif
 
 #include "../include/common.h"

util/libreboot-utils/lib/mkhtemp.c

@@ -4,9 +4,8 @@
  * Hardened mktemp (be nice to the demon).
  */
 
-#if defined(__linux__) && !defined(_GNU_SOURCE)
+#if !defined(_POSIX_C_SOURCE)
-/* for openat2 syscall on linux */
+#define _POSIX_C_SOURCE 200809L
-#define _GNU_SOURCE 1
 #endif
 
 #include <sys/types.h>

util/libreboot-utils/lib/rand.c

@@ -7,28 +7,21 @@
 #ifndef RAND_H
 #define RAND_H
 
-#ifndef _GNU_SOURCE
-#define _GNU_SOURCE 1
-#endif
-
 #ifdef __OpenBSD__
 #include <sys/param.h>
 #endif
 #include <sys/types.h>
 
-#ifndef USE_URANDOM
-#define USE_URANDOM 0
-#endif
-
-#include <errno.h>
 #if defined(USE_URANDOM) && \
     ((USE_URANDOM) > 0)
 #include <fcntl.h> /* if not arc4random: /dev/urandom */
 #elif defined(__linux__)
 #include <sys/random.h>
 #include <sys/syscall.h>
+long syscall(long number, ...);
 #endif
 
+#include <errno.h>
 #include <fcntl.h>
 #include <limits.h>
 #include <stddef.h>

util/libreboot-utils/lib/state.c

@@ -4,8 +4,8 @@
  * State machine (singleton) for nvmutil data.
  */
 
-#ifndef _GNU_SOURCE
+#ifndef _POSIX_C_SOURCE
-#define _GNU_SOURCE 1
+#define _POSIX_C_SOURCE 200809L
 #endif
 
 #include <sys/types.h>

util/libreboot-utils/lottery.c

@@ -2,6 +2,11 @@
  * Copyright (c) 2026 Leah Rowe <leah@libreboot.org>                    /| |\
    Something something non-determinism                                   / \ */
 
+#if !defined(_POSIX_C_SOURCE)
+/* for openat2 on linux */
+#define _POSIX_C_SOURCE 200809L
+#endif
+
 #include <ctype.h>
 #include <stddef.h>
 #include <stdio.h>

util/libreboot-utils/mkhtemp.c

@@ -16,9 +16,9 @@
  * while the specification that it implements evolves.
  */
 
-#if defined(__linux__) && !defined(_GNU_SOURCE)
+#if !defined(_POSIX_C_SOURCE)
 /* for openat2 on linux */
-#define _GNU_SOURCE 1
+#define _POSIX_C_SOURCE 200809L
 #endif
 
 #include <sys/types.h>

util/libreboot-utils/nvmutil.c

@@ -6,8 +6,8 @@
  * These images configure your Intel Gigabit Ethernet adapter.
  */
 
-#ifndef _GNU_SOURCE
+#ifndef _POSIX_C_SOURCE
-#define _GNU_SOURCE 1
+#define _POSIX_C_SOURCE 200809L
 #endif
 
 #include <sys/types.h>