Re: [RFC PATCH] meson: Run some compiler checks using -Wno-unused-value

[Philippe Mathieu-Daudé]

On 12/12/24 10:15, Daniel P. Berrangé wrote:
> On Thu, Dec 12, 2024 at 12:16:55AM +0100, Philippe Mathieu-Daudé wrote:
> > When running Clang static analyzer on macOS I'm getting:
>
>
> snip
>
> > Fix by explicitly disabling -Wunused-value from these meson checks.
> >
> > Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> > ---
> > RFC: Probably meson should do that in has_header_symbol() / has_type()?
>
> How are you enabling the use of static analyzers ?  There are several
> different ways to change compiler options and I vaguely recall some
> approaches can trip up meson.

I prefix my build with 'scan-build':

$ scan-build make
scan-build: Using '/usr/bin/clang' for static analysis
config-host.mak is out-of-date, running configure
C compiler for the host machine: clang (clang 16.0.0 "Apple clang 
version 16.0.0 (clang-1600.0.26.4)")

You can reproduce without using scan-build by passing
--extra-cflags=-Wunused-value to ./configure.

We have a "disable some undesirable warnings" section in
warn_flags[] in meson.build. If we want to ignore unused
we should add it there, but I'd rather not ignore them ;)

> > ---
> >   meson.build | 11 +++++++----
> >   1 file changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/meson.build b/meson.build
> > index 147097c652e..a431aa982ac 100644
> > --- a/meson.build
> > +++ b/meson.build
> > @@ -1166,7 +1166,8 @@ cocoa = dependency('appleframeworks',
> >   vmnet = dependency('appleframeworks', modules: 'vmnet', required: 
> > get_option('vmnet'))
> >   if vmnet.found() and not cc.has_header_symbol('vmnet/vmnet.h',
> >                                                 'VMNET_BRIDGED_MODE',
> > -                                              dependencies: vmnet)
> > +                                              dependencies: vmnet,
> > +                                              args: '-Wno-unused-value')
> >     vmnet = not_found
> >     if get_option('vmnet').enabled()
> >       error('vmnet.framework API is outdated')
> > @@ -2690,7 +2691,7 @@ config_host_data.set('CONFIG_RTNETLINK',
> >   config_host_data.set('CONFIG_SYSMACROS',
> >                        cc.has_header_symbol('sys/sysmacros.h', 'makedev'))
> >   config_host_data.set('HAVE_OPTRESET',
> > -                     cc.has_header_symbol('getopt.h', 'optreset'))
> > +                     cc.has_header_symbol('getopt.h', 'optreset', args: 
> > '-Wno-unused-value'))
> >   config_host_data.set('HAVE_IPPROTO_MPTCP',
> >                        cc.has_header_symbol('netinet/in.h', 'IPPROTO_MPTCP'))
> >   
> > @@ -2708,10 +2709,12 @@ config_host_data.set('HAVE_BLK_ZONE_REP_CAPACITY',
> >   # has_type
> >   config_host_data.set('CONFIG_IOVEC',
> >                        cc.has_type('struct iovec',
> > -                                 prefix: '#include <sys/uio.h>'))
> > +                                 prefix: '#include <sys/uio.h>',
> > +                                 args: '-Wno-unused-value'))
> >   config_host_data.set('HAVE_UTMPX',
> >                        cc.has_type('struct utmpx',
> > -                                 prefix: '#include <utmpx.h>'))
> > +                                 prefix: '#include <utmpx.h>',
> > +                                 args: '-Wno-unused-value'))
> >   
> >   config_host_data.set('CONFIG_EVENTFD', cc.links('''
> >     #include <sys/eventfd.h>
> > --
> > 2.45.2
>
> With regards,
> Daniel