Re: [PATCH v4 0/2] Replaced locks with lock guard macros

[Daniel Brodsky]

On Mon, Mar 23, 2020 at 6:25 AM Stefan Hajnoczi <address@hidden> wrote:
>
> On Fri, Mar 20, 2020 at 06:43:23AM -0700, address@hidden wrote:
> > /tmp/qemu-test/src/util/thread-pool.c:213:5: error: unused variable 
> > 'qemu_lockable_auto1' [-Werror,-Wunused-variable]
> >     QEMU_LOCK_GUARD(&pool->lock);
> >     ^
> > /tmp/qemu-test/src/include/qemu/lockable.h:173:29: note: expanded from 
> > macro 'QEMU_LOCK_GUARD'
>
> Apparently gcc suppresses "unused variable" warnings with g_autoptr() so
> we didn't see this warning before.
>
> clang does report them so let's silence the warning manually.  Please
> add G_GNUC_UNUSED onto the g_autoptr variable definition in the
> QEMU_LOCK_GUARD() macro:
>
>   #define QEMU_LOCK_GUARD(x) \
>       g_autoptr(QemuLockable) qemu_lockable_auto##__COUNTER__ G_GNUC_UNUSED = 
> \
>               qemu_lockable_auto_lock(QEMU_MAKE_LOCKABLE((x)))
>
> The WITH_*_LOCK_GUARD() macros should not require changes because the
> variable is both read and written.
>
> You can test locally by building with clang (llvm) instead of gcc:
>
>   ./configure --cc=clang

Using --cc=clang is causing the following error in several different places:
qemu/target/ppc/translate.c:1894:18: error: result of comparison
'target_ulong' (aka 'unsigned int') <= 4294967295
is always true [-Werror,-Wtautological-type-limit-compare]
        if (mask <= 0xffffffffu) {
            ~~~~ ^  ~~~~~~~~~~~

these errors don't come up when building with gcc. Any idea how to fix
this? Or should I just suppress it?