Re: [Boost-users] Is there a way for a library to add symbols to the standard headers ?

Subject: Re: [Boost-users] Is there a way for a library to add symbols to the standard headers ?
From: Timothy Madden (terminatorul_at_[hidden])
Date: 2010-09-03 03:53:41

On 9/2/2010 4:47 AM, Steven Watanabe wrote:
> AMDG
>
> Timothy Madden wrote:
>> To write a library to add a POSIX emulation layer on Windows, is there
>> a way to add symbols from my library to C/C++ standard library
>> headers, without getting into recursive inclusion ?
>
> Boost.TR1 does this and it's a horrible mess that only works most of the
> time.

Thank you.

I checked how TR1 achieves this functionality. Very ingenious:

        - check that the standard header <cstdio> is placed in a
          directory named include/, so the full pathname of the
          standard header would end in .../include/cstdio
        - put my own headers in an directory named libposix/
        - to get the standard header just #include <../include/cstdio>

Since my header would be in <../libposix/cstdio>, there is no recursion 
problem any more

Indeed, you were right, "it is a horrible mess that only works most of 
the time", for example if some other library wants to use the same trick 
(like Boost.TR1) to build something on top of my <cstdio>, than the 
other library needs to know about <../libposix/cstdio>, or else it will 
effectively get my symbols out of <cstdio>.

Also if the compiler implementation changes the name of the include 
directory with the standard <cstdio>, then <../libposix/cstdio> no 
longer works, but I guess that would be the case anyway because of 
content changes that come with a new compiler implementation.

Thank you,
Timothy Madden