build: Silence clang warning on older glib autoptr usage

glib's G_DEFINE_AUTOPTR_CLEANUP_FUNC() macro defines several static
inline functions, often with some of them unused, but prior to 2.57.2
did not mark the functions as such.  As a result, clang (but not gcc)
fails to build with older glib unless -Wno-unused-function is enabled.

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 20200317175534.196295-1-eblake@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/configure b/configure
index 06fcd070fb..479336bf6e 100755
--- a/configure
+++ b/configure
@@ -3851,6 +3851,26 @@ if ! compile_prog "$glib_cflags -Werror" "$glib_libs" ; then
     fi
 fi
 
+# Silence clang warnings triggered by glib < 2.57.2
+cat > $TMPC << EOF
+#include <glib.h>
+typedef struct Foo {
+    int i;
+} Foo;
+static void foo_free(Foo *f)
+{
+    g_free(f);
+}
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(Foo, foo_free);
+int main(void) { return 0; }
+EOF
+if ! compile_prog "$glib_cflags -Werror" "$glib_libs" ; then
+    if cc_has_warning_flag "-Wno-unused-function"; then
+        glib_cflags="$glib_cflags -Wno-unused-function"
+        CFLAGS="$CFLAGS -Wno-unused-function"
+    fi
+fi
+
 #########################################
 # zlib check