base gcc and _GLIBCXX_USE_C99

[Pedro Giffuni]

Hello Dimitry;


----- Messaggio originale -----
> Da: Dimitry Andric 

> I had a bit more in-depth look at our current libstdc++ configuration.
> 
> I took the original gcc 4.2.1 release tarball, modified a few autoconf
> related scripts to cope with "freebsd10.0" being the current version,
> and did a full three-stage build, though only targeting C and C++.
> 
> The libstdc++ configure script in 4.2.1 does detect a few new features
> that are not in our shipping config.h, but is does not detect any
> different settings regarding C99.
>

Not sure if libstdc++ from gcc42 sets --enable-c99 by default.
  
> The reason it does not turn on _GLIBCXX_USE_C99, is that not all of the
> C99 requirements are met, specifically <complex.h> checks fail:
> 
>   checking for ISO C99 support in <math.h>... yes
>   checking for ISO C99 support in <complex.h>... no
>   checking for ISO C99 support in <stdio.h>... yes
>   checking for ISO C99 support in <stdlib.h>... yes
>   checking for ISO C99 support in <wchar.h>... yes
>   checking for fully enabled ISO C99 support... no
> 
> The exact failure testcase goes like this:
> 
>   configure:7435: checking for ISO C99 support in <complex.h>
>   configure:7492:  /home/dim/obj/gcc-4.2.1/./gcc/xgcc -shared-libgcc 
> -B/home/dim/obj/gcc-4.2.1/./gcc -nostdinc++ 
> -L/home/dim/obj/gcc-4.2.1/i386-unknown-freebsd10.0/libstdc++-v3/src 
> -L/home/dim/obj/gcc-4.2.1/i386-unknown-freebsd10.0/libstdc++-v3/src/.libs 
> -B/home/dim/ins/gcc-4.2.1/i386-unknown-freebsd10.0/bin/ 
> -B/home/dim/ins/gcc-4.2.1/i386-unknown-freebsd10.0/lib/ -isystem 
> /home/dim/ins/gcc-4.2.1/i386-unknown-freebsd10.0/include -isystem 
> /home/dim/ins/gcc-4.2.1/i386-unknown-freebsd10.0/sys-include -c -g -O2  
> conftest.cc >&5
>   conftest.cc: In function 'int main()':
>   conftest.cc:41: error: 'clogf' was not declared in this scope
>   conftest.cc:47: error: 'cpowf' was not declared in this scope
>   conftest.cc:54: error: 'clog' was not declared in this scope
>   conftest.cc:60: error: 'cpow' was not declared in this scope
>   conftest.cc:64: error: 'ccosl' was not declared in this scope
>   conftest.cc:65: error: 'ccoshl' was not declared in this scope
>   conftest.cc:66: error: 'cexpl' was not declared in this scope
>   conftest.cc:67: error: 'clogl' was not declared in this scope
>   conftest.cc:68: error: 'csinl' was not declared in this scope
>   conftest.cc:69: error: 'csinhl' was not declared in this scope
>   conftest.cc:71: error: 'ctanl' was not declared in this scope
>   conftest.cc:72: error: 'ctanhl' was not declared in this scope
>   conftest.cc:73: error: 'cpowl' was not declared in this scope
>   configure:7498: $? = 1
> 

Those are surely in this list:
https://wiki.freebsd.org/MissingMathStuff

I think we are using stubs for libc++.

> So until we actually implement and declare those functions, we should
> probably not enable _GLIBCXX_USE_C99_COMPLEX and _GLIBCXX_USE_C99.
> 
> I have attached a diff of the other changes that can be applied on our
> current libstdc++ config file, as detected by the configure script.  I
> will probably commit that soonish, if there are no objections.
> 

Thanks, that looks useful. Of course if GLIBCXX_USE_C99 didn't necessarily
imply _GLIBCXX_USE_C99_COMPLEX it would be useful too.

> As to the missing complex functions, I am not sure.  Maybe these can be
> imported from somewhere else, e.g. NetBSD?  This is probably something
> to ask the lib/msun specialists...
> 


There is a freebsd-numerics list for people working on it.

I am using the C++ complex stuff from boost and there were
recent fixes done by Stephen Montgomery-Smith (CC'd)
and it looks like he has a FreeBSD implementation in the works.

I will open a PR as a reminder ;).

cheers,

Pedro.