[v3] C99 complex math vs. std::complex

[Paolo Carlini]

Benjamin Kosnik wrote:

>>I think it's safe to remove it because Benjamin removed back in 2001 the
>>relevant autoconf tests as obsolete: therefore nothing currently defines the
>>macro at install time and, by the way, it's also completely undocumented.
>>    
>>
>Agreed. Sorry, I should have been more careful when I removed this in 2001.
>
>Can you bring this part of the patch over to the 3.4 branch as well please?
>  
>
Sure.

>>Anyway, the below is the complete set of tweaks that I have regtested on
>>x86-linux (ongoing x86-64 too).
>>    
>>
>I too wondered about adding the complex bits to ac_enable_c99. However,
>I think this is actually a good idea, like Paolo.
>
>I was concerned that this might impact what systems have wchar_t support
>turned on, but it turns out that is separate. Or, kinda separate due to
>twisted config bits, but not likely to change with this patch. Maybe we
>should just switch to _GLIBCXX_USE_C99_foo where foo is
>(math|wchar_t|complex) instead of what we have now (which is mostly
>this). Anyway: that's for another day.
>  
>
Ok. I'll try to disentangle a bit this soon. Indeed, there is an XXX in 
a comment...

>So, go for it. While you're changing acinclude.m4, can you change my
>comment 
>
>  # Check for the existence of <math.h> complex functions.
>
>to
>
>  # Check for the existence of <complex.h> complex functions.
>  
>
Will do!

Paolo.