From ee6d9760206b59baa8f2d9adb09cf730ca2d24a4 Mon Sep 17 00:00:00 2001
From: Andres Freund <andres@anarazel.de>
Date: Wed, 28 Dec 2022 10:09:48 -0800
Subject: [PATCH] wip: perl: If supported, use gcc's system_header pragma to
 hide warnings

Author:
Reviewed-by:
Discussion: https://postgr.es/m/
Backpatch:
---
 meson.build            | 9 +++++++++
 src/pl/plperl/plperl.h | 8 ++++++++
 2 files changed, 17 insertions(+)

diff --git a/meson.build b/meson.build
index b872470cdfe..1532b04c62a 100644
--- a/meson.build
+++ b/meson.build
@@ -1408,6 +1408,15 @@ if not cc.compiles(c99_test, name: 'c99', args: test_c_args)
   endif
 endif
 
+# 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
+if cc.compiles('#pragma GCC system_header',
+    name: 'pragma system header',
+    args: test_c_args + ['-Werror=unknown-pragmas'])
+  cdata.set('HAVE_PRAGMA_SYSTEM_HEADER', 1)
+endif
+
 sizeof_long = cc.sizeof('long', args: test_c_args)
 cdata.set('SIZEOF_LONG', sizeof_long)
 if sizeof_long == 8
diff --git a/src/pl/plperl/plperl.h b/src/pl/plperl/plperl.h
index 5243f308bd5..2656a0376ee 100644
--- a/src/pl/plperl/plperl.h
+++ b/src/pl/plperl/plperl.h
@@ -74,6 +74,14 @@
 #define HAS_BOOL 1
 #endif
 
+/*
+ * At least in newer versions the perl headers trigger a lot of warnings with
+ * our compiler flags. The system_header pragma hides warnings from within the
+ * rest of this file, if supported.
+ */
+#if HAVE_PRAGMA_SYSTEM_HEADER
+#pragma GCC system_header
+#endif
 
 /*
  * Get the basic Perl API.  We use PERL_NO_GET_CONTEXT mode so that our code
-- 
2.38.0