Remove the CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE switch

GCC supports "#pragma GCC diagnostic" since version 4.6, and
Clang seems to support it, too, since its early versions 3.x.
That means that our minimum required compiler versions all support
this pragma already and we can remove the test from configure and
all the related #ifdefs in the code.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20200710045515.25986-1-thuth@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

configure

@@ -5728,31 +5728,6 @@ if compile_prog "" "" ; then
     linux_magic_h=yes
 fi
 
-########################################
-# check whether we can disable warning option with a pragma (this is needed
-# to silence warnings in the headers of some versions of external libraries).
-# This test has to be compiled with -Werror as otherwise an unknown pragma is
-# only a warning.
-#
-# If we can't selectively disable warning in the code, disable -Werror so that
-# the build doesn't fail anyway.
-
-pragma_disable_unused_but_set=no
-cat > $TMPC << EOF
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wstrict-prototypes"
-#pragma GCC diagnostic pop
-
-int main(void) {
-    return 0;
-}
-EOF
-if compile_prog "-Werror" "" ; then
-    pragma_diagnostic_available=yes
-else
-    werror=no
-fi
-
 ########################################
 # check if we have valgrind/valgrind.h
 
@@ -7689,10 +7664,6 @@ if test "$linux_magic_h" = "yes" ; then
   echo "CONFIG_LINUX_MAGIC_H=y" >> $config_host_mak
 fi
 
-if test "$pragma_diagnostic_available" = "yes" ; then
-  echo "CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE=y" >> $config_host_mak
-fi
-
 if test "$valgrind_h" = "yes" ; then
   echo "CONFIG_VALGRIND_H=y" >> $config_host_mak
 fi

include/ui/gtk.h

@@ -1,15 +1,11 @@
 #ifndef UI_GTK_H
 #define UI_GTK_H
 
-#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
 /* Work around an -Wstrict-prototypes warning in GTK headers */
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wstrict-prototypes"
-#endif
 #include <gtk/gtk.h>
-#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
 #pragma GCC diagnostic pop
-#endif
 
 #include <gdk/gdkkeysyms.h>
 

include/ui/qemu-pixman.h

@@ -7,14 +7,10 @@
 #define QEMU_PIXMAN_H
 
 /* pixman-0.16.0 headers have a redundant declaration */
-#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wredundant-decls"
-#endif
 #include <pixman.h>
-#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
 #pragma GCC diagnostic pop
-#endif
 
 /*
  * pixman image formats are defined to be native endian,

scripts/decodetree.py

@@ -1327,12 +1327,10 @@ def main():
     # but we can't tell which ones.  Prevent issues from the compiler by
     # suppressing redundant declaration warnings.
     if anyextern:
-        output("#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE\n",
+        output("#pragma GCC diagnostic push\n",
-               "# pragma GCC diagnostic push\n",
+               "#pragma GCC diagnostic ignored \"-Wredundant-decls\"\n",
-               "# pragma GCC diagnostic ignored \"-Wredundant-decls\"\n",
+               "#ifdef __clang__\n"
-               "# ifdef __clang__\n"
                "#  pragma GCC diagnostic ignored \"-Wtypedef-redefinition\"\n",
-               "# endif\n",
                "#endif\n\n")
 
     out_pats = {}
@@ -1347,9 +1345,7 @@ def main():
     output('\n')
 
     if anyextern:
-        output("#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE\n",
+        output("#pragma GCC diagnostic pop\n\n")
-               "# pragma GCC diagnostic pop\n",
-               "#endif\n\n")
 
     for n in sorted(formats.keys()):
         f = formats[n]

ui/gtk.c

@@ -1996,14 +1996,10 @@ static GSList *gd_vc_gfx_init(GtkDisplayState *s, VirtualConsole *vc,
              * proper replacement (native opengl support) is only
              * available in 3.16+.  Silence the warning if possible.
              */
-#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
-#endif
             gtk_widget_set_double_buffered(vc->gfx.drawing_area, FALSE);
-#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
 #pragma GCC diagnostic pop
-#endif
             vc->gfx.dcl.ops = &dcl_egl_ops;
         }
     } else

util/coroutine-ucontext.c

@@ -251,8 +251,8 @@ Coroutine *qemu_coroutine_new(void)
 }
 
 #ifdef CONFIG_VALGRIND_H
-#if defined(CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE) && !defined(__clang__)
 /* Work around an unused variable in the valgrind.h macro... */
+#if !defined(__clang__)
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wunused-but-set-variable"
 #endif
@@ -260,7 +260,7 @@ static inline void valgrind_stack_deregister(CoroutineUContext *co)
 {
     VALGRIND_STACK_DEREGISTER(co->valgrind_stack_id);
 }
-#if defined(CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE) && !defined(__clang__)
+#if !defined(__clang__)
 #pragma GCC diagnostic pop
 #endif
 #endif