[libvirt PATCH] util: squelch G_DEFINE_TYPE volatile warnings with GCC 11

[Daniel P. Berrangé <berrange@xxxxxxxxxx>]

In this previous commit:

  commit 65491a2dfe00bfcf9f09a8d6eab60234b56c8cc4
  Author: Martin Kletzander <mkletzan@xxxxxxxxxx>
  Date:   Thu Nov 12 13:58:53 2020 +0100

    Do not disable incompatible-pointer-types-discards-qualifiers

We selectively rewrite G_DEFINE_TYPE to avoid warnings about
mismatched volatile/non-volatile pointers that appeared with
CLang when using GLib2 >= 2.67

We have now just hit the reverse problem, GCC >= 11 has started
warning about mismatched volatile/non-volatile pointers but only
with GLib2 < 2.67. The new GLib2 avoids the warning, as does
older GCC.

Signed-off-by: Daniel P. Berrangé <berrange@xxxxxxxxxx>
---
 src/util/glibcompat.h | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/src/util/glibcompat.h b/src/util/glibcompat.h
index 457f6ba797..455324925f 100644
--- a/src/util/glibcompat.h
+++ b/src/util/glibcompat.h
@@ -22,7 +22,10 @@
 #include <glib/gstdio.h>
 #include <glib-object.h>
 
-#if defined(__clang__) && GLIB_CHECK_VERSION(2, 67, 0)
+#if GLIB_CHECK_VERSION(2, 67, 0)
+
+# if defined(__clang__)
+
 /*
  * Clang detects (valid) issue in G_DEFINE_TYPE and derivatives starting with
  * glib >= 2.67.0.  See https://gitlab.gnome.org/GNOME/glib/-/issues/600
@@ -34,16 +37,36 @@
  * is defined in glib (with a very low probability of being changed thanks to a
  * comment above it).
  */
-# undef _G_DEFINE_TYPE_EXTENDED_BEGIN
+#  undef _G_DEFINE_TYPE_EXTENDED_BEGIN
 
-# define _G_DEFINE_TYPE_EXTENDED_BEGIN(TypeName, type_name, TYPE_PARENT, flags) \
+#  define _G_DEFINE_TYPE_EXTENDED_BEGIN(TypeName, type_name, TYPE_PARENT, flags) \
     _Pragma("GCC diagnostic push") \
     _Pragma("GCC diagnostic ignored \"-Wincompatible-pointer-types-discards-qualifiers\"") \
     _G_DEFINE_TYPE_EXTENDED_BEGIN_PRE(TypeName, type_name, TYPE_PARENT) \
     _G_DEFINE_TYPE_EXTENDED_BEGIN_REGISTER(TypeName, type_name, TYPE_PARENT, flags) \
     _Pragma("GCC diagnostic pop")
 
-#endif /* __clang__ */
+# endif /* __clang__ */
+
+#else /* GLib < 2.67.0 */
+
+/*
+ * ...meanwhile GCC >= 11 has started issuing warnings about volatile
+ * from the old G_DEFINE_TYPE macro impl. IOW the new macros impls fixed
+ * new GCC, but broke CLang
+ */
+# if !defined(__clang__) && __GNUC_PREREQ (11, 0)
+#  undef _G_DEFINE_TYPE_EXTENDED_BEGIN
+
+#  define _G_DEFINE_TYPE_EXTENDED_BEGIN(TypeName, type_name, TYPE_PARENT, flags) \
+    _Pragma("GCC diagnostic push") \
+    _Pragma("GCC diagnostic ignored \"-Wincompatible-pointer-types\"") \
+    _G_DEFINE_TYPE_EXTENDED_BEGIN_PRE(TypeName, type_name, TYPE_PARENT) \
+    _G_DEFINE_TYPE_EXTENDED_BEGIN_REGISTER(TypeName, type_name, TYPE_PARENT, flags) \
+    _Pragma("GCC diagnostic pop")
+# endif /* !clang */
+
+#endif /* GLib < 2.67.0 */
 
 gchar * vir_g_canonicalize_filename(const gchar *filename,
                                     const gchar *relative_to);
-- 
2.25.4