Re: [PATCH] meson.build: Don't look for libudev for static builds

[Paolo Bonzini <pbonzini@redhat.com>]

On 03/10/20 09:24, 罗勇刚(Yonggang Luo) wrote:
> 
> 
> On Fri, Oct 2, 2020 at 9:11 PM Peter Maydell <peter.maydell@linaro.org
> <mailto:peter.maydell@linaro.org>> wrote:
>>
>> On Fri, 2 Oct 2020 at 14:05, Paolo Bonzini <pbonzini@redhat.com
> <mailto:pbonzini@redhat.com>> wrote:
>> >
>> > On 02/10/20 14:35, Peter Maydell wrote:
>> > >
>> > > It would be better to do the "see if a static library is present"
>> > > test. This isn't too hard to do in configure (compare that
>> > > six line fix to the detection of libgio). Hopefully it is
>> > > not too hard to do in meson ?
>> >
>> > Yes, something like:
>> >
>> > if enable_static
>> >   skeleton = 'int main(void) { return 0; }'
>> >   if not cc.links(skeleton, dependencies: libudev)
>> >     if get_option('mpath').enabled()
>> >         error('Cannot link with libudev')
>> >       else
>> >         warning('Cannot link with libudev, disabling')
>> >         libudev = not_found
>> >       endif
>> >     endif
>> >   endif
>> > endif
>>
>> This duplicates the information that the thing that depends
>> on libudev is mpath. Can we put this in a wrapper around
>> dependency() so that we could just say something like
>>   libudev = compile_checked_dependency('libudev',
>>                        required: get_option('mpath').enabled(),
>>                        static: enable_static)
>>
> Hi Bonzini,
> This looks like a frequently used function, can we upstrem to meson?

Yes, I think adding a "links" argument to dependency (similar to
find_library's has_headers argument) makes sense.  That would be written

    dependency('libudev',
               required: get_option('mpath').enabled(),
               static: enable_static,
               links: skeleton)

But anyway that shouldn't be a blocker for more improvements to qemu's
meson.build.  Now that we have 5-10 dependencies converted we have a
clearer idea of how to abstract the tests.

Paolo