Re: [boost] [tr1] Help needed with Darwin port

Subject: Re: [boost] [tr1] Help needed with Darwin port
From: John Maddock (john_at_[hidden])
Date: 2009-01-13 13:10:02

>> * Is it possible to detect the Darwin version number (to separate
>> 10.0 from 9.x)?
>
> A quick find/grep through the system headers did not come up with
> anything obvious.

:-(

> I would not attempt to detect the version using a shell variable like
> OSTYPE, though, since that would presumably detect the version of
> Darwin that you are running on, not the version that you are compiling
> for.  It's possible to have multiple versions of Apple's developer
> tools installed, and each one of them can support SDKs from older
> systems, so the version of Darwin that's running would not be a
> reliable indicator of where the stdc++ headers are stored.
>
>> * Do you know what happens if someone installs gcc from source (ie
>> not from Apples developer tools)?
>
> It's been some time since I've done this, but my recollection is that
> by default, the stdc++ headers that come with gcc get installed into a
> deep, deep subdirectory of /usr/local whose location is known only to
> gcc.  This is done so you have have multiple versions of gcc and stdc+
> + installed simultaneously.
>
>
> I think that perhaps there's another way out of this situation.
>
> I'm assuming that the reason you can't simply #include <iostream> is
> that you are defining a header whose name is also <iostream>, and
> attempting to include the stdc++ version of the header simply leads to
> infinite recursion.
>
> I believe that gcc has a non-standard extension called #include_next
> that is designed to handle exactly this situation.  It includes
> another file, but searches for it _only_ in the directories that come
> later in the search path than the current directory.  You can read
> more about it at:

Sigh, this is what I used to use, but changed it because of bug reports: the 
issue is that if you install boost in say /usr/include (as some Linux 
distro's do) then #include_next can never get you from /usr/include to the 
unknown location of the g++ std lib headers :-(

I think what I'm going to do for now is revert to using #include_next on 
Darwin, and hope folks don't install Boost into a system directory!

Thanks for your help with this, John.