use C2x style header versioning for include guards

1 files changed, 6 insertions, 2 deletions

diff --git a/stdlib.h b/stdlib.h
index 9350398..54e43df 100644
--- a/stdlib.h
+++ b/stdlib.h
@@ -1,5 +1,9 @@
-#ifndef __STDLIB_H__
-#define __STDLIB_H__
+#ifndef __STDC_VERSION_STDLIB_H__
+#if defined __STDC_VERSION__
+#define __STDC_VERSION_STDLIB_H__ __STDC_VERSION__
+#else
+#define __STDC_VERSION_STDLIB_H__ 1
+#endif
 
 /*
 UNG's Not GNU