@@ -179,10 +179,24 @@
 AS_IF([test x"$PLUGIN_SUFFIX" != x""], [
 	AC_SUBST(USE_SRCS_PLUGINS, '${SRCS_PLUGINS}')
 	AC_SUBST(TESTPLUGIN, "plugin")
 	AC_DEFINE(OF_HAVE_PLUGINS, 1, [Whether we have plugin support])
 ])
+
+AC_MSG_CHECKING(whether we need -D_GNU_SOURCE)
+AC_EGREP_CPP(yes, [
+	#include <stdlib.h>
+
+	#ifdef __GLIBC__
+	yes
+	#endif
+], [
+	CPPFLAGS="-D_GNU_SOURCE $CPPFLAGS"
+	AC_MSG_RESULT(yes)
+], [
+	AC_MSG_RESULT(no)
+])
 
 objc_runtime="ObjFW runtime"
 AC_CHECK_HEADER(objc/objc.h)
 AC_MSG_CHECKING(which Objective C runtime to use)
 AC_ARG_ENABLE(runtime,