[PATCH v2 0/8] buildsys: More fixes to use GCC on macOS

[PATCH v2 0/8] buildsys: More fixes to use GCC on macOS

[Philippe Mathieu-Daudé via]

Few fixes to be able to use GCC extensions which are not
available on Clang.

Since RFC:
- Split Clang __builtin_available() patch
- Do not un-inline qemu_thread_jit_execute/write
- Do not use #pragma diagnostic
- Demote ui/cocoa key arrays to static const
- Lookup scripts/entitlement.sh script once again
- Pass filtered QEMU_OBJCFLAGS configure -> meson
- Disable out-of-line atomic operations on Aarch64

Philippe Mathieu-Daudé (8):
  osdep: Avoid using Clang-specific __builtin_available()
  osdep: Ignore 'unguarded-availability-new' warnings on macOS Catalina
  meson: Resolve the entitlement.sh script once for good
  configure: Disable out-of-line atomic operations on Aarch64
  meson: Log QEMU_CXXFLAGS content in summary
  configure: Pass filtered QEMU_OBJCFLAGS to meson
  audio: Rename coreaudio extension to use Objective-C compiler
  ui/cocoa: Constify qkeycode translation arrays

 audio/{coreaudio.c => coreaudio.m} |  0
 audio/meson.build                  |  2 +-
 configure                          | 35 ++++++++++++++++++++++++++++++
 include/qemu/osdep.h               | 10 +++------
 meson.build                        | 11 ++++++++--
 ui/cocoa.m                         |  4 ++--
 6 files changed, 50 insertions(+), 12 deletions(-)
 rename audio/{coreaudio.c => coreaudio.m} (100%)

-- 
2.34.1

[PATCH v2 1/8] osdep: Avoid using Clang-specific __builtin_available()

[Philippe Mathieu-Daudé via]

Remove the Clang specific __builtin_available() to allow building
with GCC, otherwise we get:

  include/qemu/osdep.h: In function 'qemu_thread_jit_write':
  include/qemu/osdep.h:787:9: warning: implicit declaration of function '__builtin_available'; did you mean '__builtin_scalbl'? [-Wimplicit-function-declaration]
    787 |     if (__builtin_available(macOS 11.0, *)) {
        |         ^~~~~~~~~~~~~~~~~~~
        |         __builtin_scalbl
  include/qemu/osdep.h:787:9: warning: nested extern declaration of '__builtin_available' [-Wnested-externs]
  include/qemu/osdep.h:787:29: error: 'macOS' undeclared (first use in this function)
    787 |     if (__builtin_available(macOS 11.0, *)) {
        |                             ^~~~~
  include/qemu/osdep.h:787:29: note: each undeclared identifier is reported only once for each function it appears in
  include/qemu/osdep.h:787:34: error: expected ')' before numeric constant
    787 |     if (__builtin_available(macOS 11.0, *)) {
        |                            ~     ^~~~~
        |                                  )

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 include/qemu/osdep.h | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index d1660d67fa..aecd2f66ec 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -777,16 +777,12 @@ size_t qemu_get_host_physmem(void);
     MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_VERSION_11_0
 static inline void qemu_thread_jit_execute(void)
 {
-    if (__builtin_available(macOS 11.0, *)) {
-        pthread_jit_write_protect_np(true);
-    }
+    pthread_jit_write_protect_np(true);
 }
 
 static inline void qemu_thread_jit_write(void)
 {
-    if (__builtin_available(macOS 11.0, *)) {
-        pthread_jit_write_protect_np(false);
-    }
+    pthread_jit_write_protect_np(false);
 }
 #else
 static inline void qemu_thread_jit_write(void) {}
-- 
2.34.1

[PATCH v2 2/8] osdep: Ignore 'unguarded-availability-new' warnings on macOS Catalina

[Philippe Mathieu-Daudé via]

When building with GCC on macOS Catalina we get 2254 times:

  include/qemu/osdep.h:780:5: warning: 'pthread_jit_write_protect_np' is only available on macOS 11.0 or newer [-Wunguarded-availability-new]
      pthread_jit_write_protect_np(true);
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fix by using a stricker toolchain version low range, replacing
MAC_OS_X_VERSION_MAX_ALLOWED by MAC_OS_X_VERSION_MIN_REQUIRED.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 include/qemu/osdep.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index aecd2f66ec..1e7a002339 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -774,7 +774,7 @@ size_t qemu_get_host_physmem(void);
  * for the current thread.
  */
 #if defined(MAC_OS_VERSION_11_0) && \
-    MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_VERSION_11_0
+    MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_VERSION_11_0
 static inline void qemu_thread_jit_execute(void)
 {
     pthread_jit_write_protect_np(true);
-- 
2.34.1

[PATCH v2 3/8] meson: Resolve the entitlement.sh script once for good

[Philippe Mathieu-Daudé via]

Commit 235b523dba ("meson: Use find_program() to resolve the
entitlement.sh script") didn't correctly fixed the issue, as
the script is still resolved for each target. Move the check
earlier, before processing each target.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 meson.build | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/meson.build b/meson.build
index df25e7a5e7..287be51ff2 100644
--- a/meson.build
+++ b/meson.build
@@ -2894,6 +2894,10 @@ common_all = static_library('common',
 
 feature_to_c = find_program('scripts/feature_to_c.sh')
 
+if targetos == 'darwin'
+  entitlement = find_program('scripts/entitlement.sh')
+endif
+
 emulators = {}
 foreach target : target_dirs
   config_target = config_target_mak[target]
@@ -3051,7 +3055,6 @@ foreach target : target_dirs
         install_input += meson.current_source_dir() / entitlements
       endif
 
-      entitlement = find_program('scripts/entitlement.sh')
       emulators += {exe['name'] : custom_target(exe['name'],
                    input: build_input,
                    output: exe['name'],
-- 
2.34.1

[PATCH v2 4/8] configure: Disable out-of-line atomic operations on Aarch64

[Philippe Mathieu-Daudé via]

GCC 10.1 introduced the -moutline-atomics option on Aarch64.
This options is enabled by default, and triggers a link failure:

  Undefined symbols for architecture arm64:
    "___aarch64_cas1_acq_rel", referenced from:
        _qmp_migrate_recover in migration_migration.c.o
        _cpu_atomic_cmpxchgb_mmu in accel_tcg_cputlb.c.o
        _cpu_atomic_fetch_sminb_mmu in accel_tcg_cputlb.c.o
        _cpu_atomic_fetch_uminb_mmu in accel_tcg_cputlb.c.o
        _cpu_atomic_fetch_smaxb_mmu in accel_tcg_cputlb.c.o
        _cpu_atomic_fetch_umaxb_mmu in accel_tcg_cputlb.c.o
        _cpu_atomic_smin_fetchb_mmu in accel_tcg_cputlb.c.o
        ...
    "___aarch64_ldadd4_acq_rel", referenced from:
        _multifd_recv_new_channel in migration_multifd.c.o
        _monitor_event in monitor_hmp.c.o
        _handle_hmp_command in monitor_hmp.c.o
        _colo_compare_finalize in net_colo-compare.c.o
        _flatview_unref in softmmu_memory.c.o
        _virtio_scsi_hotunplug in hw_scsi_virtio-scsi.c.o
        _tcg_register_thread in tcg_tcg.c.o
        ...
    "___aarch64_swp4_acq", referenced from:
        _qemu_spin_lock in softmmu_cpu-timers.c.o
        _cpu_get_ticks in softmmu_cpu-timers.c.o
        _qemu_spin_lock in softmmu_icount.c.o
        _cpu_exec in accel_tcg_cpu-exec.c.o
        _page_flush_tb_1.isra.0 in accel_tcg_translate-all.c.o
        _page_entry_lock in accel_tcg_translate-all.c.o
        _do_tb_phys_invalidate in accel_tcg_translate-all.c.o
        ...

QEMU implements its own atomic operations using C11 builtin helpers.
Disable the GCC out-of-line atomic ops.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>

Clearly out of my understanding, but at least it links and the qtests
pass.
---
 configure | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/configure b/configure
index 06c03cebd3..3217aa22cb 100755
--- a/configure
+++ b/configure
@@ -2826,6 +2826,18 @@ else
   avx512f_opt="no"
 fi
 
+#########################################
+# Disable out-of-line atomic operations.
+
+case "$cpu" in
+  aarch64)
+    write_c_skeleton;
+    if compile_prog "$CPU_CFLAGS -Werror -mno-outline-atomics" "" ; then
+      CPU_CFLAGS="-mno-outline-atomics $CPU_CFLAGS"
+    fi
+    ;;
+esac
+
 ########################################
 # check if __[u]int128_t is usable.
 
-- 
2.34.1

[PATCH v2 5/8] meson: Log QEMU_CXXFLAGS content in summary

[Philippe Mathieu-Daudé via]

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 meson.build | 1 +
 1 file changed, 1 insertion(+)

diff --git a/meson.build b/meson.build
index 287be51ff2..215c253683 100644
--- a/meson.build
+++ b/meson.build
@@ -3305,6 +3305,7 @@ if link_args.length() > 0
   summary_info += {'LDFLAGS':         ' '.join(link_args)}
 endif
 summary_info += {'QEMU_CFLAGS':       config_host['QEMU_CFLAGS']}
+summary_info += {'QEMU_CXXFLAGS':     config_host['QEMU_CXXFLAGS']}
 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

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

[Philippe Mathieu-Daudé via]

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

[PATCH v2 7/8] audio: Rename coreaudio extension to use Objective-C compiler

[Philippe Mathieu-Daudé via]

The coreaudio library includes Objective-C declarations (using the
caret '^' symbol to declare block references [*]). When building
with a C compiler we get:

  [175/839] Compiling C object libcommon.fa.p/audio_coreaudio.c.o
    In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk/System/Library/Frameworks/CoreAudio.framework/Headers/CoreAudio.h:18,
                     from ../../audio/coreaudio.c:26:
    /Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk/System/Library/Frameworks/CoreAudio.framework/Headers/AudioHardware.h:162:2: error: expected identifier or '(' before '^' token
      162 | (^AudioObjectPropertyListenerBlock)(    UInt32                              inNumberAddresses,
          |  ^
    FAILED: libcommon.fa.p/audio_coreaudio.c.o

Rename the file to use the Objective-C default extension (.m) so
meson calls the correct compiler.

[*] https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/WorkingwithBlocks/WorkingwithBlocks.html

Reviewed-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 audio/{coreaudio.c => coreaudio.m} | 0
 audio/meson.build                  | 2 +-
 2 files changed, 1 insertion(+), 1 deletion(-)
 rename audio/{coreaudio.c => coreaudio.m} (100%)

diff --git a/audio/coreaudio.c b/audio/coreaudio.m
similarity index 100%
rename from audio/coreaudio.c
rename to audio/coreaudio.m
diff --git a/audio/meson.build b/audio/meson.build
index d9b295514f..94dab16891 100644
--- a/audio/meson.build
+++ b/audio/meson.build
@@ -7,7 +7,7 @@ softmmu_ss.add(files(
   'wavcapture.c',
 ))
 
-softmmu_ss.add(when: coreaudio, if_true: files('coreaudio.c'))
+softmmu_ss.add(when: coreaudio, if_true: files('coreaudio.m'))
 softmmu_ss.add(when: dsound, if_true: files('dsoundaudio.c', 'audio_win_int.c'))
 
 audio_modules = {}
-- 
2.34.1

[PATCH v2 8/8] ui/cocoa: Constify qkeycode translation arrays

[Philippe Mathieu-Daudé via]

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 ui/cocoa.m | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ui/cocoa.m b/ui/cocoa.m
index 30702d31a5..7a3a610212 100644
--- a/ui/cocoa.m
+++ b/ui/cocoa.m
@@ -651,7 +651,7 @@ QemuCocoaView *cocoaView;
 
     /* translates Macintosh keycodes to QEMU's keysym */
 
-    int without_control_translation[] = {
+    static const int without_control_translation[] = {
         [0 ... 0xff] = 0,   // invalid key
 
         [kVK_UpArrow]       = QEMU_KEY_UP,
@@ -666,7 +666,7 @@ QemuCocoaView *cocoaView;
         [kVK_Delete]        = QEMU_KEY_BACKSPACE,
     };
 
-    int with_control_translation[] = {
+    static const int with_control_translation[] = {
         [0 ... 0xff] = 0,   // invalid key
 
         [kVK_UpArrow]       = QEMU_KEY_CTRL_UP,
-- 
2.34.1

Re: [PATCH v2 2/8] osdep: Ignore 'unguarded-availability-new' warnings on macOS Catalina

[Akihiko Odaki]

On Wed, Feb 16, 2022 at 2:01 AM Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>
> When building with GCC on macOS Catalina we get 2254 times:
>
>   include/qemu/osdep.h:780:5: warning: 'pthread_jit_write_protect_np' is only available on macOS 11.0 or newer [-Wunguarded-availability-new]
>       pthread_jit_write_protect_np(true);
>       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Fix by using a stricker toolchain version low range, replacing
> MAC_OS_X_VERSION_MAX_ALLOWED by MAC_OS_X_VERSION_MIN_REQUIRED.
>
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>  include/qemu/osdep.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index aecd2f66ec..1e7a002339 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -774,7 +774,7 @@ size_t qemu_get_host_physmem(void);
>   * for the current thread.
>   */
>  #if defined(MAC_OS_VERSION_11_0) && \
> -    MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_VERSION_11_0
> +    MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_VERSION_11_0
>  static inline void qemu_thread_jit_execute(void)
>  {
>      pthread_jit_write_protect_np(true);
> --
> 2.34.1
>

This should be squashed with "[PATCH v2 1/8] osdep: Avoid using
Clang-specific __builtin_available()"; Removing __builtin_available
makes it incompatible with macOS < 11.0, hence this change is needed.

Re: [PATCH v2 4/8] configure: Disable out-of-line atomic operations on Aarch64

[Akihiko Odaki]

On Wed, Feb 16, 2022 at 2:01 AM Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>
> GCC 10.1 introduced the -moutline-atomics option on Aarch64.
> This options is enabled by default, and triggers a link failure:
>
>   Undefined symbols for architecture arm64:
>     "___aarch64_cas1_acq_rel", referenced from:
>         _qmp_migrate_recover in migration_migration.c.o
>         _cpu_atomic_cmpxchgb_mmu in accel_tcg_cputlb.c.o
>         _cpu_atomic_fetch_sminb_mmu in accel_tcg_cputlb.c.o
>         _cpu_atomic_fetch_uminb_mmu in accel_tcg_cputlb.c.o
>         _cpu_atomic_fetch_smaxb_mmu in accel_tcg_cputlb.c.o
>         _cpu_atomic_fetch_umaxb_mmu in accel_tcg_cputlb.c.o
>         _cpu_atomic_smin_fetchb_mmu in accel_tcg_cputlb.c.o
>         ...
>     "___aarch64_ldadd4_acq_rel", referenced from:
>         _multifd_recv_new_channel in migration_multifd.c.o
>         _monitor_event in monitor_hmp.c.o
>         _handle_hmp_command in monitor_hmp.c.o
>         _colo_compare_finalize in net_colo-compare.c.o
>         _flatview_unref in softmmu_memory.c.o
>         _virtio_scsi_hotunplug in hw_scsi_virtio-scsi.c.o
>         _tcg_register_thread in tcg_tcg.c.o
>         ...
>     "___aarch64_swp4_acq", referenced from:
>         _qemu_spin_lock in softmmu_cpu-timers.c.o
>         _cpu_get_ticks in softmmu_cpu-timers.c.o
>         _qemu_spin_lock in softmmu_icount.c.o
>         _cpu_exec in accel_tcg_cpu-exec.c.o
>         _page_flush_tb_1.isra.0 in accel_tcg_translate-all.c.o
>         _page_entry_lock in accel_tcg_translate-all.c.o
>         _do_tb_phys_invalidate in accel_tcg_translate-all.c.o
>         ...
>
> QEMU implements its own atomic operations using C11 builtin helpers.
> Disable the GCC out-of-line atomic ops.
>
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
> Cc: Stefan Hajnoczi <stefanha@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
>
> Clearly out of my understanding, but at least it links and the qtests
> pass.
> ---
>  configure | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/configure b/configure
> index 06c03cebd3..3217aa22cb 100755
> --- a/configure
> +++ b/configure
> @@ -2826,6 +2826,18 @@ else
>    avx512f_opt="no"
>  fi
>
> +#########################################
> +# Disable out-of-line atomic operations.
> +
> +case "$cpu" in
> +  aarch64)
> +    write_c_skeleton;
> +    if compile_prog "$CPU_CFLAGS -Werror -mno-outline-atomics" "" ; then
> +      CPU_CFLAGS="-mno-outline-atomics $CPU_CFLAGS"
> +    fi
> +    ;;
> +esac
> +
>  ########################################
>  # check if __[u]int128_t is usable.
>
> --
> 2.34.1
>

This change would (slightly) increase the code size and is harmful to
the other proper GCC installations. The flag should be specified by
the user (or the user should fix the GCC installation.)

Re: [PATCH v2 4/8] configure: Disable out-of-line atomic operations on Aarch64

[Richard Henderson]

On 2/16/22 04:01, Philippe Mathieu-Daudé via wrote:
> GCC 10.1 introduced the -moutline-atomics option on Aarch64.
> This options is enabled by default, and triggers a link failure:
> 
>    Undefined symbols for architecture arm64:
>      "___aarch64_cas1_acq_rel", referenced from:
>          _qmp_migrate_recover in migration_migration.c.o
>          _cpu_atomic_cmpxchgb_mmu in accel_tcg_cputlb.c.o
>          _cpu_atomic_fetch_sminb_mmu in accel_tcg_cputlb.c.o
>          _cpu_atomic_fetch_uminb_mmu in accel_tcg_cputlb.c.o
>          _cpu_atomic_fetch_smaxb_mmu in accel_tcg_cputlb.c.o
>          _cpu_atomic_fetch_umaxb_mmu in accel_tcg_cputlb.c.o
>          _cpu_atomic_smin_fetchb_mmu in accel_tcg_cputlb.c.o
>          ...
>      "___aarch64_ldadd4_acq_rel", referenced from:
>          _multifd_recv_new_channel in migration_multifd.c.o
>          _monitor_event in monitor_hmp.c.o
>          _handle_hmp_command in monitor_hmp.c.o
>          _colo_compare_finalize in net_colo-compare.c.o
>          _flatview_unref in softmmu_memory.c.o
>          _virtio_scsi_hotunplug in hw_scsi_virtio-scsi.c.o
>          _tcg_register_thread in tcg_tcg.c.o
>          ...
>      "___aarch64_swp4_acq", referenced from:
>          _qemu_spin_lock in softmmu_cpu-timers.c.o
>          _cpu_get_ticks in softmmu_cpu-timers.c.o
>          _qemu_spin_lock in softmmu_icount.c.o
>          _cpu_exec in accel_tcg_cpu-exec.c.o
>          _page_flush_tb_1.isra.0 in accel_tcg_translate-all.c.o
>          _page_entry_lock in accel_tcg_translate-all.c.o
>          _do_tb_phys_invalidate in accel_tcg_translate-all.c.o
>          ...
> 
> QEMU implements its own atomic operations using C11 builtin helpers.
> Disable the GCC out-of-line atomic ops.
> 
> Signed-off-by: Philippe Mathieu-Daudé<f4bug@amsat.org>
> ---
> Cc: Stefan Hajnoczi<stefanha@redhat.com>
> Cc: Paolo Bonzini<pbonzini@redhat.com>
> 
> Clearly out of my understanding, but at least it links and the qtests
> pass.
> ---
>   configure | 12 ++++++++++++
>   1 file changed, 12 insertions(+)

These should have been supplied by libgcc.a, which we're supposed to be linking against. 
Something is wrong with your installation.


r~

Re: [PATCH v2 4/8] configure: Disable out-of-line atomic operations on Aarch64

[Philippe Mathieu-Daudé via]

On 16/2/22 11:19, Richard Henderson wrote:
> On 2/16/22 04:01, Philippe Mathieu-Daudé via wrote:
>> GCC 10.1 introduced the -moutline-atomics option on Aarch64.
>> This options is enabled by default, and triggers a link failure:
>>
>>    Undefined symbols for architecture arm64:
>>      "___aarch64_cas1_acq_rel", referenced from:
>>          _qmp_migrate_recover in migration_migration.c.o
>>          _cpu_atomic_cmpxchgb_mmu in accel_tcg_cputlb.c.o
>>          _cpu_atomic_fetch_sminb_mmu in accel_tcg_cputlb.c.o
>>          _cpu_atomic_fetch_uminb_mmu in accel_tcg_cputlb.c.o
>>          _cpu_atomic_fetch_smaxb_mmu in accel_tcg_cputlb.c.o
>>          _cpu_atomic_fetch_umaxb_mmu in accel_tcg_cputlb.c.o
>>          _cpu_atomic_smin_fetchb_mmu in accel_tcg_cputlb.c.o
>>          ...
>>      "___aarch64_ldadd4_acq_rel", referenced from:
>>          _multifd_recv_new_channel in migration_multifd.c.o
>>          _monitor_event in monitor_hmp.c.o
>>          _handle_hmp_command in monitor_hmp.c.o
>>          _colo_compare_finalize in net_colo-compare.c.o
>>          _flatview_unref in softmmu_memory.c.o
>>          _virtio_scsi_hotunplug in hw_scsi_virtio-scsi.c.o
>>          _tcg_register_thread in tcg_tcg.c.o
>>          ...
>>      "___aarch64_swp4_acq", referenced from:
>>          _qemu_spin_lock in softmmu_cpu-timers.c.o
>>          _cpu_get_ticks in softmmu_cpu-timers.c.o
>>          _qemu_spin_lock in softmmu_icount.c.o
>>          _cpu_exec in accel_tcg_cpu-exec.c.o
>>          _page_flush_tb_1.isra.0 in accel_tcg_translate-all.c.o
>>          _page_entry_lock in accel_tcg_translate-all.c.o
>>          _do_tb_phys_invalidate in accel_tcg_translate-all.c.o
>>          ...
>>
>> QEMU implements its own atomic operations using C11 builtin helpers.
>> Disable the GCC out-of-line atomic ops.
>>
>> Signed-off-by: Philippe Mathieu-Daudé<f4bug@amsat.org>
>> ---
>> Cc: Stefan Hajnoczi<stefanha@redhat.com>
>> Cc: Paolo Bonzini<pbonzini@redhat.com>
>>
>> Clearly out of my understanding, but at least it links and the qtests
>> pass.
>> ---
>>   configure | 12 ++++++++++++
>>   1 file changed, 12 insertions(+)
> 
> These should have been supplied by libgcc.a, which we're supposed to be 
> linking against. Something is wrong with your installation.

I don't have gobjc/g++ installed, so ./configure defaulted to Clang to
compile these languages, but compiled C files using GCC. At the end the
Clang linker is used (the default c++ symlink).

Could there be a mismatch between Clang (-mno-outline-atomics) and GCC
(-moutline-atomics)?

Re: [PATCH v2 4/8] configure: Disable out-of-line atomic operations on Aarch64

[Akihiko Odaki]

On 2022/02/17 0:08, Philippe Mathieu-Daudé wrote:
> On 16/2/22 11:19, Richard Henderson wrote:
>> On 2/16/22 04:01, Philippe Mathieu-Daudé via wrote:
>>> GCC 10.1 introduced the -moutline-atomics option on Aarch64.
>>> This options is enabled by default, and triggers a link failure:
>>>
>>>    Undefined symbols for architecture arm64:
>>>      "___aarch64_cas1_acq_rel", referenced from:
>>>          _qmp_migrate_recover in migration_migration.c.o
>>>          _cpu_atomic_cmpxchgb_mmu in accel_tcg_cputlb.c.o
>>>          _cpu_atomic_fetch_sminb_mmu in accel_tcg_cputlb.c.o
>>>          _cpu_atomic_fetch_uminb_mmu in accel_tcg_cputlb.c.o
>>>          _cpu_atomic_fetch_smaxb_mmu in accel_tcg_cputlb.c.o
>>>          _cpu_atomic_fetch_umaxb_mmu in accel_tcg_cputlb.c.o
>>>          _cpu_atomic_smin_fetchb_mmu in accel_tcg_cputlb.c.o
>>>          ...
>>>      "___aarch64_ldadd4_acq_rel", referenced from:
>>>          _multifd_recv_new_channel in migration_multifd.c.o
>>>          _monitor_event in monitor_hmp.c.o
>>>          _handle_hmp_command in monitor_hmp.c.o
>>>          _colo_compare_finalize in net_colo-compare.c.o
>>>          _flatview_unref in softmmu_memory.c.o
>>>          _virtio_scsi_hotunplug in hw_scsi_virtio-scsi.c.o
>>>          _tcg_register_thread in tcg_tcg.c.o
>>>          ...
>>>      "___aarch64_swp4_acq", referenced from:
>>>          _qemu_spin_lock in softmmu_cpu-timers.c.o
>>>          _cpu_get_ticks in softmmu_cpu-timers.c.o
>>>          _qemu_spin_lock in softmmu_icount.c.o
>>>          _cpu_exec in accel_tcg_cpu-exec.c.o
>>>          _page_flush_tb_1.isra.0 in accel_tcg_translate-all.c.o
>>>          _page_entry_lock in accel_tcg_translate-all.c.o
>>>          _do_tb_phys_invalidate in accel_tcg_translate-all.c.o
>>>          ...
>>>
>>> QEMU implements its own atomic operations using C11 builtin helpers.
>>> Disable the GCC out-of-line atomic ops.
>>>
>>> Signed-off-by: Philippe Mathieu-Daudé<f4bug@amsat.org>
>>> ---
>>> Cc: Stefan Hajnoczi<stefanha@redhat.com>
>>> Cc: Paolo Bonzini<pbonzini@redhat.com>
>>>
>>> Clearly out of my understanding, but at least it links and the qtests
>>> pass.
>>> ---
>>>   configure | 12 ++++++++++++
>>>   1 file changed, 12 insertions(+)
>>
>> These should have been supplied by libgcc.a, which we're supposed to 
>> be linking against. Something is wrong with your installation.
> 
> I don't have gobjc/g++ installed, so ./configure defaulted to Clang to
> compile these languages, but compiled C files using GCC. At the end the
> Clang linker is used (the default c++ symlink).
> 
> Could there be a mismatch between Clang (-mno-outline-atomics) and GCC
> (-moutline-atomics)?

I think you have to instruct Clang to use libgcc instead of compiler-rt 
and link the objects with GCC. Here is the documentation of Clang about 
the runtime I could find:
https://clang.llvm.org/docs/Toolchain.html#libgcc-s-gnu

Re: [PATCH v2 4/8] configure: Disable out-of-line atomic operations on Aarch64

[Philippe Mathieu-Daudé via]

On 16/2/22 17:42, Akihiko Odaki wrote:
> On 2022/02/17 0:08, Philippe Mathieu-Daudé wrote:
>> On 16/2/22 11:19, Richard Henderson wrote:
>>> On 2/16/22 04:01, Philippe Mathieu-Daudé via wrote:
>>>> GCC 10.1 introduced the -moutline-atomics option on Aarch64.
>>>> This options is enabled by default, and triggers a link failure:
>>>>
>>>>    Undefined symbols for architecture arm64:
>>>>      "___aarch64_cas1_acq_rel", referenced from:
>>>>          _qmp_migrate_recover in migration_migration.c.o
>>>>          _cpu_atomic_cmpxchgb_mmu in accel_tcg_cputlb.c.o
>>>>          _cpu_atomic_fetch_sminb_mmu in accel_tcg_cputlb.c.o
>>>>          _cpu_atomic_fetch_uminb_mmu in accel_tcg_cputlb.c.o
>>>>          _cpu_atomic_fetch_smaxb_mmu in accel_tcg_cputlb.c.o
>>>>          _cpu_atomic_fetch_umaxb_mmu in accel_tcg_cputlb.c.o
>>>>          _cpu_atomic_smin_fetchb_mmu in accel_tcg_cputlb.c.o
>>>>          ...
>>>>      "___aarch64_ldadd4_acq_rel", referenced from:
>>>>          _multifd_recv_new_channel in migration_multifd.c.o
>>>>          _monitor_event in monitor_hmp.c.o
>>>>          _handle_hmp_command in monitor_hmp.c.o
>>>>          _colo_compare_finalize in net_colo-compare.c.o
>>>>          _flatview_unref in softmmu_memory.c.o
>>>>          _virtio_scsi_hotunplug in hw_scsi_virtio-scsi.c.o
>>>>          _tcg_register_thread in tcg_tcg.c.o
>>>>          ...
>>>>      "___aarch64_swp4_acq", referenced from:
>>>>          _qemu_spin_lock in softmmu_cpu-timers.c.o
>>>>          _cpu_get_ticks in softmmu_cpu-timers.c.o
>>>>          _qemu_spin_lock in softmmu_icount.c.o
>>>>          _cpu_exec in accel_tcg_cpu-exec.c.o
>>>>          _page_flush_tb_1.isra.0 in accel_tcg_translate-all.c.o
>>>>          _page_entry_lock in accel_tcg_translate-all.c.o
>>>>          _do_tb_phys_invalidate in accel_tcg_translate-all.c.o
>>>>          ...
>>>>
>>>> QEMU implements its own atomic operations using C11 builtin helpers.
>>>> Disable the GCC out-of-line atomic ops.
>>>>
>>>> Signed-off-by: Philippe Mathieu-Daudé<f4bug@amsat.org>
>>>> ---
>>>> Cc: Stefan Hajnoczi<stefanha@redhat.com>
>>>> Cc: Paolo Bonzini<pbonzini@redhat.com>
>>>>
>>>> Clearly out of my understanding, but at least it links and the qtests
>>>> pass.
>>>> ---
>>>>   configure | 12 ++++++++++++
>>>>   1 file changed, 12 insertions(+)
>>>
>>> These should have been supplied by libgcc.a, which we're supposed to 
>>> be linking against. Something is wrong with your installation.
>>
>> I don't have gobjc/g++ installed, so ./configure defaulted to Clang to
>> compile these languages, but compiled C files using GCC. At the end the
>> Clang linker is used (the default c++ symlink).
>>
>> Could there be a mismatch between Clang (-mno-outline-atomics) and GCC
>> (-moutline-atomics)?
> 
> I think you have to instruct Clang to use libgcc instead of compiler-rt 
> and link the objects with GCC. Here is the documentation of Clang about 
> the runtime I could find:
> https://clang.llvm.org/docs/Toolchain.html#libgcc-s-gnu

Thanks for the pointer. And the next section is
https://clang.llvm.org/docs/Toolchain.html#atomics-library :)

   Clang does not currently automatically link against libatomic when
    using libgcc_s. You may need to manually add -latomic to support
   this configuration when using non-native atomic operations (if you
   see link errors referring to __atomic_* functions).

I'll try that.

Re: [PATCH v2 4/8] configure: Disable out-of-line atomic operations on Aarch64

[Peter Maydell]

On Wed, 16 Feb 2022 at 17:18, Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
> Thanks for the pointer. And the next section is
> https://clang.llvm.org/docs/Toolchain.html#atomics-library :)
>
>    Clang does not currently automatically link against libatomic when
>     using libgcc_s. You may need to manually add -latomic to support
>    this configuration when using non-native atomic operations (if you
>    see link errors referring to __atomic_* functions).

We deliberately don't link against libatomic at the moment...

-- PMM

Re: [PATCH v2 4/8] configure: Disable out-of-line atomic operations on Aarch64

[Richard Henderson]

On 2/17/22 04:18, Philippe Mathieu-Daudé wrote:
> On 16/2/22 17:42, Akihiko Odaki wrote:
>> On 2022/02/17 0:08, Philippe Mathieu-Daudé wrote:
>>> On 16/2/22 11:19, Richard Henderson wrote:
>>>> These should have been supplied by libgcc.a, which we're supposed to be linking 
>>>> against. Something is wrong with your installation.
>>>
>>> I don't have gobjc/g++ installed, so ./configure defaulted to Clang to
>>> compile these languages, but compiled C files using GCC. At the end the
>>> Clang linker is used (the default c++ symlink).

This is another form of compiler mis-configuration.
If you don't have g++ to go with gcc, use --cxx=false to avoid picking up a different 
compiler.

>>> Could there be a mismatch between Clang (-mno-outline-atomics) and GCC
>>> (-moutline-atomics)?

I have no idea if those options do the same thing.

>> I think you have to instruct Clang to use libgcc instead of compiler-rt and link the 
>> objects with GCC. Here is the documentation of Clang about the runtime I could find:
>> https://clang.llvm.org/docs/Toolchain.html#libgcc-s-gnu
> 
> Thanks for the pointer. And the next section is
> https://clang.llvm.org/docs/Toolchain.html#atomics-library :)
> 
>    Clang does not currently automatically link against libatomic when
>     using libgcc_s. You may need to manually add -latomic to support
>    this configuration when using non-native atomic operations (if you
>    see link errors referring to __atomic_* functions).
> 
> I'll try that.

-moutline-atomics is *not* the same as libatomic.
You should not need libatomic at all.


r~

Re: [PATCH v2 4/8] configure: Disable out-of-line atomic operations on Aarch64

[Paolo Bonzini]

On 2/18/22 02:46, Richard Henderson wrote:
>>>>
>>>> I don't have gobjc/g++ installed, so ./configure defaulted to Clang to
>>>> compile these languages, but compiled C files using GCC. At the end the
>>>> Clang linker is used (the default c++ symlink).
> 
> This is another form of compiler mis-configuration.
> If you don't have g++ to go with gcc, use --cxx=false to avoid picking 
> up a different compiler.

This would be the kind of problem that this test is trying to cover:

     if do_cxx $CXXFLAGS $EXTRA_CXXFLAGS $CONFIGURE_CXXFLAGS $QEMU_CXXFLAGS -o $TMPE $TMPCXX $TMPO $QEMU_LDFLAGS; then
         # C++ compiler $cxx works ok with C compiler $cc
         :
     else
         echo "C++ compiler $cxx does not work with C compiler $cc"
         echo "Disabling C++ specific optional code"
         cxx=
     fi

In the past it detected issues with libasan/libtsan incompatibilities.
We should either add a test for atomic operations, or just drop the
test.

Paolo

Re: [PATCH v2 4/8] configure: Disable out-of-line atomic operations on Aarch64

[Paolo Bonzini]

On 2/15/22 18:01, Philippe Mathieu-Daudé via wrote:
> +
> +case "$cpu" in
> +  aarch64)
> +    write_c_skeleton;
> +    if compile_prog "$CPU_CFLAGS -Werror -mno-outline-atomics" "" ; then
> +      CPU_CFLAGS="-mno-outline-atomics $CPU_CFLAGS"
> +    fi
> +    ;;

Apart from the question of whether/how to work around this issue, this 
should not be added to CPU_CFLAGS.  CPU_CFLAGS is only for things that 
change the ABI.

Paolo

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

[Paolo Bonzini]

On 2/15/22 18:01, Philippe Mathieu-Daudé via wrote:
> 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>

Acked-by: Paolo Bonzini <pbonzini@redhat.com>

> ---
>   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')}

Re: [PATCH v2 4/8] configure: Disable out-of-line atomic operations on Aarch64

[Philippe Mathieu-Daudé]

On 18/2/22 16:36, Paolo Bonzini wrote:
> On 2/18/22 02:46, Richard Henderson wrote:
>>>>>
>>>>> I don't have gobjc/g++ installed, so ./configure defaulted to Clang to
>>>>> compile these languages, but compiled C files using GCC. At the end 
>>>>> the
>>>>> Clang linker is used (the default c++ symlink).
>>
>> This is another form of compiler mis-configuration.
>> If you don't have g++ to go with gcc, use --cxx=false to avoid picking 
>> up a different compiler.
> 
> This would be the kind of problem that this test is trying to cover:
> 
>      if do_cxx $CXXFLAGS $EXTRA_CXXFLAGS $CONFIGURE_CXXFLAGS 
> $QEMU_CXXFLAGS -o $TMPE $TMPCXX $TMPO $QEMU_LDFLAGS; then
>          # C++ compiler $cxx works ok with C compiler $cc
>          :
>      else
>          echo "C++ compiler $cxx does not work with C compiler $cc"
>          echo "Disabling C++ specific optional code"
>          cxx=
>      fi
> 
> In the past it detected issues with libasan/libtsan incompatibilities.
> We should either add a test for atomic operations, or just drop the
> test.

We shouldn't assume gcc is GCC:

$ c++ --version
Apple clang version 13.0.0 (clang-1300.0.29.30)
Target: arm64-apple-darwin21.3.0
Thread model: posix
InstalledDir: 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

$ g++ --version
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr 
--with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/4.2.1
Apple clang version 13.0.0 (clang-1300.0.29.30)
Target: arm64-apple-darwin21.3.0
Thread model: posix
InstalledDir: 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

$ gcc --version
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr 
--with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/4.2.1
Apple clang version 13.0.0 (clang-1300.0.29.30)
Target: arm64-apple-darwin21.3.0
Thread model: posix
InstalledDir: 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

$ clang --version
Apple clang version 13.0.0 (clang-1300.0.29.30)
Target: arm64-apple-darwin21.3.0
Thread model: posix
InstalledDir: 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin