1 files changed, 28 insertions, 0 deletions
diff --git a/src/include/c.h b/src/include/c.h
index 7567ef7888b..9e1583e0d10 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -381,6 +381,34 @@ typedef void (*pg_funcptr_t) (void);
  */
 #define FLEXIBLE_ARRAY_MEMBER	/* empty */
 
+/*
+ * Does the compiler support #pragma GCC system_header? We optionally use it
+ * to avoid warnings that we can't fix (e.g. in the perl headers).
+ * See https://gcc.gnu.org/onlinedocs/cpp/System-Headers.html
+ *
+ * Headers for which we do not want to show compiler warnings can,
+ * conditionally, use #pragma GCC system_header to avoid warnings. Obviously
+ * this should only be used for external headers over which we do not have
+ * control.
+ *
+ * Support for the pragma is tested here, instead of during configure, as gcc
+ * also warns about the pragma being used in a .c file. It's surprisingly hard
+ * to get autoconf to use .h as the file-ending. Looks like gcc has
+ * implemented the pragma since the 2000, so this test should suffice.
+ *
+ *
+ * Alternatively, we could add the include paths for problematic headers with
+ * -isystem, but that is a larger hammer and is harder to search for.
+ *
+ * A more granular alternative would be to use #pragma GCC diagnostic
+ * push/ignored/pop, but gcc warns about unknown warnings being ignored, so
+ * every to-be-ignored-temporarily compiler warning would require its own
+ * pg_config.h symbol and #ifdef.
+ */
+#ifdef __GNUC__
+#define HAVE_PRAGMA_GCC_SYSTEM_HEADER	1
+#endif
+
 
 /* ----------------------------------------------------------------
  *				Section 2:	bool, true, false