[PATCH v2 6/8] configure: Pass filtered QEMU_OBJCFLAGS to meson

["Philippe Mathieu-Daudé via" <qemu-devel@nongnu.org>]

Filter unsupported Objective-C options, to avoid
'unknown-warning-option' warnings when using Clang:

  [34/373] Compiling Objective-C object libcommon.fa.p/audio_coreaudio.m.o
  warning: unknown warning option '-Wold-style-declaration'; did you mean '-Wout-of-line-declaration'? [-Wunknown-warning-option]
  warning: unknown warning option '-Wimplicit-fallthrough=2'; did you mean '-Wimplicit-fallthrough'? [-Wunknown-warning-option]
  2 warnings generated.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 configure   | 23 +++++++++++++++++++++++
 meson.build |  5 ++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/configure b/configure
index 3217aa22cb..df6eaec067 100755
--- a/configure
+++ b/configure
@@ -77,6 +77,7 @@ TMPB="qemu-conf"
 TMPC="${TMPDIR1}/${TMPB}.c"
 TMPO="${TMPDIR1}/${TMPB}.o"
 TMPCXX="${TMPDIR1}/${TMPB}.cxx"
+TMPM="${TMPDIR1}/${TMPB}.m"
 TMPE="${TMPDIR1}/${TMPB}.exe"
 
 rm -f config.log
@@ -148,6 +149,10 @@ do_cxx() {
     do_compiler "$cxx" $CPU_CFLAGS "$@"
 }
 
+do_objc() {
+    do_compiler "$objcc" $CPU_CFLAGS "$@"
+}
+
 # Append $2 to the variable named $1, with space separation
 add_to() {
     eval $1=\${$1:+\"\$$1 \"}\$2
@@ -1616,10 +1621,27 @@ cc_has_warning_flag() {
     compile_prog "-Werror $optflag" ""
 }
 
+objcc_has_warning_flag() {
+    cat > $TMPM <<EOF
+int main(void) { return 0; }
+EOF
+
+    # Use the positive sense of the flag when testing for -Wno-wombat
+    # support (gcc will happily accept the -Wno- form of unknown
+    # warning options).
+    optflag="$(echo $1 | sed -e 's/^-Wno-/-W/')"
+    do_objc -Werror $optflag \
+      $OBJCFLAGS $EXTRA_OBJCFLAGS $CONFIGURE_OBJCFLAGS $QEMU_OBJCFLAGS \
+      -o $TMPE $TMPM $QEMU_LDFLAGS
+}
+
 for flag in $gcc_flags; do
     if cc_has_warning_flag $flag ; then
         QEMU_CFLAGS="$QEMU_CFLAGS $flag"
     fi
+    if objcc_has_warning_flag $flag ; then
+        QEMU_OBJCFLAGS="$QEMU_OBJCFLAGS $flag"
+    fi
 done
 
 if test "$stack_protector" != "no"; then
@@ -3579,6 +3601,7 @@ echo "LD=$ld" >> $config_host_mak
 echo "CFLAGS_NOPIE=$CFLAGS_NOPIE" >> $config_host_mak
 echo "QEMU_CFLAGS=$QEMU_CFLAGS" >> $config_host_mak
 echo "QEMU_CXXFLAGS=$QEMU_CXXFLAGS" >> $config_host_mak
+echo "QEMU_OBJCFLAGS=$QEMU_OBJCFLAGS" >> $config_host_mak
 echo "GLIB_CFLAGS=$glib_cflags" >> $config_host_mak
 echo "GLIB_LIBS=$glib_libs" >> $config_host_mak
 echo "GLIB_VERSION=$(pkg-config --modversion glib-2.0)" >> $config_host_mak
diff --git a/meson.build b/meson.build
index 215c253683..7b78235a39 100644
--- a/meson.build
+++ b/meson.build
@@ -199,9 +199,11 @@ if get_option('fuzzing')
 endif
 
 add_global_arguments(config_host['QEMU_CFLAGS'].split(),
-                     native: false, language: ['c', 'objc'])
+                     native: false, language: ['c'])
 add_global_arguments(config_host['QEMU_CXXFLAGS'].split(),
                      native: false, language: 'cpp')
+add_global_arguments(config_host['QEMU_OBJCFLAGS'].split(),
+                     native: false, language: ['objc'])
 add_global_link_arguments(config_host['QEMU_LDFLAGS'].split(),
                           native: false, language: ['c', 'cpp', 'objc'])
 
@@ -3306,6 +3308,7 @@ if link_args.length() > 0
 endif
 summary_info += {'QEMU_CFLAGS':       config_host['QEMU_CFLAGS']}
 summary_info += {'QEMU_CXXFLAGS':     config_host['QEMU_CXXFLAGS']}
+summary_info += {'QEMU_OBJCFLAGS':    config_host['QEMU_OBJCFLAGS']}
 summary_info += {'QEMU_LDFLAGS':      config_host['QEMU_LDFLAGS']}
 summary_info += {'profiler':          config_host.has_key('CONFIG_PROFILER')}
 summary_info += {'link-time optimization (LTO)': get_option('b_lto')}
-- 
2.34.1