3 files changed, 9 insertions, 4 deletions
diff --git a/ioops.c b/ioops.c
index e2b9136..c1eeddc 100644
--- a/ioops.c
+++ b/ioops.c
@@ -1,4 +1,6 @@
-#define _GNU_SOURCE
+#ifndef _GNU_SOURCE
+# define _GNU_SOURCE
+#endif
 #include <unistd.h>
 #include <sys/types.h>
 #include <sys/stat.h>
diff --git a/proc.c b/proc.c
index b0c577c..76e3c93 100644
--- a/proc.c
+++ b/proc.c
@@ -1,4 +1,6 @@
-#define _GNU_SOURCE
+#ifndef _GNU_SOURCE
+# define _GNU_SOURCE
+#endif
 #include <sched.h>
 #include <sys/wait.h>
 #include <sys/types.h>
diff --git a/xmalloc.c b/xmalloc.c
index 75319ff..368e18d 100644
--- a/xmalloc.c
+++ b/xmalloc.c
@@ -4,8 +4,9 @@
  * Copyright 2014, 2015 Tobias Klauser
  * Subject to the GPL, version 2.
  */
-
-#define _GNU_SOURCE
+#ifndef _GNU_SOURCE
+# define _GNU_SOURCE
+#endif
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>