[PATCH] configure: Disable thread-safety warnings on macOS

[PATCH] configure: Disable thread-safety warnings on macOS

[Thomas Huth]

The enablement of -Wthread-safety broke compilation on macOS (if
-Werror is enabled, like in our CI). Disable it there by default
until the problems are resolved.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 configure | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/configure b/configure
index 2a8a9be8a1..9a0f8cdb4e 100755
--- a/configure
+++ b/configure
@@ -1230,7 +1230,10 @@ add_to warn_flags -Wendif-labels
 add_to warn_flags -Wexpansion-to-defined
 add_to warn_flags -Wimplicit-fallthrough=2
 add_to warn_flags -Wmissing-format-attribute
-add_to warn_flags -Wthread-safety
+
+if test "$targetos" != "darwin"; then
+    add_to warn_flags -Wthread-safety
+fi
 
 nowarn_flags=
 add_to nowarn_flags -Wno-initializer-overrides
-- 
2.31.1

Re: [PATCH] configure: Disable thread-safety warnings on macOS

[Kevin Wolf]

Am 01.03.2023 um 12:34 hat Thomas Huth geschrieben:
> The enablement of -Wthread-safety broke compilation on macOS (if
> -Werror is enabled, like in our CI). Disable it there by default
> until the problems are resolved.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>

This is simpler than what I attempted (test compiling something using
the same TSA features as the failing code), but didn't actually work.
Since I don't have access to macOS, it's hard for me to improve the
configure test. So I'm fine with just doing this instead.

Acked-by: Kevin Wolf <kwolf@redhat.com>

For reference, below my failed alternative attempt at a configure patch,
which somehow still enabled TSA on macOS and therefore still fails to
build.

Kevin


diff --git a/configure b/configure
index 2a8a9be8a1..970ee31889 100755
--- a/configure
+++ b/configure
@@ -228,6 +228,7 @@ cross_prefix=""
 host_cc="cc"
 stack_protector=""
 safe_stack=""
+tsa=""
 use_containers="yes"
 gdb_bin=$(command -v "gdb-multiarch" || command -v "gdb")

@@ -854,6 +855,10 @@ for opt do
   ;;
   --disable-safe-stack) safe_stack="no"
   ;;
+  --enable-tsa) tsa="yes"
+  ;;
+  --disable-tsa) tsa="no"
+  ;;
   --enable-cfi)
       cfi="true";
       meson_option_add -Db_lto=true
@@ -1023,6 +1028,7 @@ Advanced options (experts only):
   --with-devices-ARCH=NAME override default configs/devices
   --enable-debug           enable common debug build options
   --enable-sanitizers      enable default sanitizers
+  --enable-tsa             enable TSA (Thread Safety Analysis)
   --enable-tsan            enable thread sanitizer
   --disable-werror         disable compilation abort on warning
   --disable-stack-protector disable compiler-provided stack protection
@@ -1230,7 +1236,6 @@ add_to warn_flags -Wendif-labels
 add_to warn_flags -Wexpansion-to-defined
 add_to warn_flags -Wimplicit-fallthrough=2
 add_to warn_flags -Wmissing-format-attribute
-add_to warn_flags -Wthread-safety

 nowarn_flags=
 add_to nowarn_flags -Wno-initializer-overrides
@@ -1308,6 +1313,28 @@ EOF
   fi
 fi

+if test "$tsa" != "no"; then
+  cat > $TMPC << EOF
+typedef int __attribute__((capability("mutex"))) Lock;
+Lock lock;
+static void __attribute__((assert_capability(lock))) assert_lock(void) {}
+static void __attribute__((requires_capability(lock))) require_lock(void) {}
+int main(void)
+{
+    assert_lock();
+    require_lock();
+    return 0;
+}
+EOF
+  flag="-Wthread-safety"
+  if compile_object "-Werror $flag"; then
+    QEMU_CFLAGS="$QEMU_CFLAGS $flag"
+    tsa="yes"
+  elif test "$tsa" = yes; then
+    error_exit "Thread Safety Analysis not supported"
+  fi
+fi
+
 # Our module code doesn't support Windows
 if test "$modules" = "yes" && test "$mingw32" = "yes" ; then
   error_exit "Modules are not available for Windows"
@@ -2378,6 +2405,9 @@ if test "$have_asan_iface_fiber" = "yes" ; then
     echo "CONFIG_ASAN_IFACE_FIBER=y" >> $config_host_mak
 fi

+if test "$tsa" = "yes"; then
+    echo "CONFIG_TSA=y" >> $config_host_mak
+fi
 if test "$have_tsan" = "yes" && test "$have_tsan_iface_fiber" = "yes" ; then
     echo "CONFIG_TSAN=y" >> $config_host_mak
 fi
diff --git a/meson.build b/meson.build
index 77d2ae87e4..a793eaacc5 100644
--- a/meson.build
+++ b/meson.build
@@ -3842,6 +3842,7 @@ else
 endif
 summary_info += {'gprof':             gprof_info}
 summary_info += {'gcov':              get_option('b_coverage')}
+summary_info += {'thread safety analysis (TSA)': config_host.has_key('CONFIG_TSA')}
 summary_info += {'thread sanitizer':  config_host.has_key('CONFIG_TSAN')}
 summary_info += {'CFI support':       get_option('cfi')}
 if get_option('cfi')

Re: [PATCH] configure: Disable thread-safety warnings on macOS

[Peter Maydell]

On Wed, 1 Mar 2023 at 13:33, Kevin Wolf <kwolf@redhat.com> wrote:
>
> Am 01.03.2023 um 12:34 hat Thomas Huth geschrieben:
> > The enablement of -Wthread-safety broke compilation on macOS (if
> > -Werror is enabled, like in our CI). Disable it there by default
> > until the problems are resolved.
> >
> > Signed-off-by: Thomas Huth <thuth@redhat.com>
>
> This is simpler than what I attempted (test compiling something using
> the same TSA features as the failing code), but didn't actually work.
> Since I don't have access to macOS, it's hard for me to improve the
> configure test. So I'm fine with just doing this instead.
>
> Acked-by: Kevin Wolf <kwolf@redhat.com>

I've applied this to master because it fixes the CI job, but
we should probably look more closely at what's going on,
because it seems plausible to me that it's something that we could
hit on Linux too with either a newer or older version of clang.

thanks
-- PMM