how to leave currently undefined directives

[Ian Lance Taylor]

Mark Galeck <mark_galeck@pacbell.net> writes:

>>What you 
>> could do with it, is "precompile" each header file, not in the sense currently 
>
>> used, but in such a way that you could then for each #include "foobar.h" line 
>>in 
>>
>> a C/C++ source file, include the "precompiled" header instead, and the result 
>>of 
>>
>> the compilation of the C/C++ source would be the same.  
>
>>What would be the goal?  
>
> The goal is as stated above (if I am not understanding your meaning of "goal", 
> please correct me)

I suppose I mean "goal" in a larger sense, which is to say, in the sense
in which it would be useful for gcc to have such a feature.  What is the
purpose of this work?  Why is it desirable to be able to "precompile" a
header file in the sense that you describe?


>>And how would you handle
>
> #ifdef FOO
> #include "foo.h"
> #endif
>
>
> As specified in the post and illustrated by my example - 

Sorry, I missed that.

How would you handle

#ifdef FOO
#define X "foo.h"
#else
#define X "bar.h"
#endif
#include X

?

Ian