Fwd: Re: Detecting musl at compile and/or configure time

[Chris Hall <musl@gmch.uk>]

On 29/06/2019 14:27, A. Wilcox wrote:
> On 06/29/19 06:48, Chris Hall wrote:
>>
>> Is there a supported way of detecting that one is building against 
>> the musl libc ?
...
> The musl libc specifically does not have a FTM (feature test macro)
> because it aims to be an exact implementation of C11 / POSIX and
> therefore it has no "quirks" to detect.

I too aim for perfection, but find that I approach it asymptotically :-)

However, restating the question in those terms: how should I detect that 
one is *not* building against some library which is *not* musl ?  [Given 
that other libraries may be equally discrete.]

...
> See here for more information:
> 
> https://wiki.musl-libc.org/faq.html#Q:-Why-is-there-no-%3Ccode%3E__MUSL__%3C/code%3E-macro?

FWIW: I read https://www.musl-libc.org/faq.html, but did not also find 
the wiki's FAQ :-(

> Is there a reason you wish to detect musl at configure/compile time?
> Perhaps if we knew the reason, we could help you make your code more
> portable and/or not require such detection.

I have a little build system which tries to detect the "usual suspects" 
automatically, even without a full configure/cmake/etc. step.  If the 
detection process fails, it generates a warning and the user must (at 
least) add a '-Dxxx' to suppress that.

I confess I have only recently stumbled across musl.  Perhaps systems 
which default to musl are so rare that I can, as a practical matter, 
ignore them ?  The question then is whether to add a '-DqLIB_MUSL' gizmo 
to my build stuff -- so that "musl-gcc -DqLIB_MUSL" will do the trick.

Thanks,

Chris