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-rw-r--r--misc/sys/cdefs.h16
1 files changed, 16 insertions, 0 deletions
diff --git a/misc/sys/cdefs.h b/misc/sys/cdefs.h
index 74f9a49b05..06523bfe9c 100644
--- a/misc/sys/cdefs.h
+++ b/misc/sys/cdefs.h
@@ -464,4 +464,20 @@
 # define __glibc_macro_warning(msg)
 #endif
 
+/* Support for generic selection (ISO C11) is available in GCC since
+   version 4.9.  Previous versions do not provide generic selection,
+   even though they might set __STDC_VERSION__ to 201112L, when in
+   -std=c11 mode.  Thus, we must check for !defined __GNUC__ when
+   testing __STDC_VERSION__ for generic selection support.
+   On the other hand, Clang also defines __GNUC__, so a clang-specific
+   check is required to enable the use of generic selection.  */
+#if __GNUC_PREREQ (4, 9) \
+    || __glibc_clang_has_extension (c_generic_selections) \
+    || (!defined __GNUC__ && defined __STDC_VERSION__ \
+	&& __STDC_VERSION__ >= 201112L)
+# define __HAVE_GENERIC_SELECTION 1
+#else
+# define __HAVE_GENERIC_SELECTION 0
+#endif
+
 #endif	 /* sys/cdefs.h */