Re: [PATCH] meson: fix botched compile check conversions

[Paolo Bonzini <pbonzini@redhat.com>]

On 11/16/21 12:13, Daniel P. Berrangé wrote:
> On Tue, Nov 16, 2021 at 10:38:34AM +0100, Paolo Bonzini wrote:
>> Fix a bunch of incorrect conversions from configure to Meson, which result
>> in different outcomes with --extra-cflags=-Werror.
>>
>> pthread_setname_np needs "#define _GNU_SOURCE" on Linux (which I am using
>> also for the non-Linux check, so that it correctly fails with an error
>> about having too few parameters).
>>
>> Fix struct checks to use has_type instead of has_symbol, and "#define
>> _GNU_SOURCE" too in the case of struct mmsghdr.
> 
> Ok, so relies on fact that passing an incorrect number of arguments
> is a fatal error, when function prototypes are available, even
> without -Werror being set.
> 
> Side note, GCC looks to be trying to make explicit function prototypes
> mandatory at last
> 
>    https://linuxplumbersconf.org/event/11/contributions/1014/

Yes, and that's also why Meson adds the -Werror=implicit-declaration 
option; these days it's simply too dangerous to assume a function is 
present, if it links but you don't really know which header it comes from.

Paolo