Re: Strange gcc-3.0.1 preprocessor

[Nick Kurshev <nickols_k at mail dot ru>]

Hello, Neil!
On Sun, 14 Oct 2001 16:12:22 +0100, you wrote:

> Nick Kurshev wrote:-
> 
> > In file included from biewlib/biewlib.h:25,
> >                  from biewlib/bbio.h:21,
> >                  from biewlib/bbio.c:26:
> > biewlib/sysdep/_sys_dep.h:30:14: warning: pasting "/" and "__MACHINE__" does not give a valid preprocessing token
> > biewlib/sysdep/_sys_dep.h:30:22: biewlib/sysdep/__MACHINE__/__config.h: No such file or directory
> > biewlib/sysdep/_sys_dep.h:31:14: warning: pasting "/" and "__MACHINE__" does not give a valid preprocessing token
> > biewlib/sysdep/_sys_dep.h:31:22: biewlib/sysdep/__MACHINE__/_inlines.h: No such file or directory
> > 
> > Only one question: Is it a bug or is it a new feature of gcc-3.0.1?
> 
> The warning tells you the problem.  Do you know what ## does?
> 
It was only way to build such trick. Else how you will notice compiler to build preprocessor string
without space characters?
Well, the same code with space characters around __MACHINE__:
source:
    #define _INLINES <biewlib/sysdep/ __MACHINE__ /_inlines.h>
    #define __CONFIG <biewlib/sysdep/ __MACHINE__ /__config.h>
    #include __CONFIG
    #include _INLINES
output:
biewlib/sysdep/_sys_dep.h:30:22: biewlib/sysdep/ ia32 /__config.h: No such file or directory
biewlib/sysdep/_sys_dep.h:31:22: biewlib/sysdep/ ia32 /_inlines.h: No such file or directory
> > Any previouse versions of gcc since 2.7.2.1 upto 2.95.3 handle this
> > code correctly.
> 
> They are incorrect; from the code it would appear they used to expand
> __MACHINE__.  That macro should not be expanded, since it is being
> operated on by ##.
> 
> I suspect you can get the result you want by losing the ##.
Well, other trick:
command:
gcc -D__MACHINE__='"ia32"'
source:
    #define _INLINES <"biewlib/sysdep/"__MACHINE__"/_inlines.h">
    #define __CONFIG <"biewlib/sysdep/"__MACHINE__"/__config.h">
    #include __CONFIG
    #include _INLINES
output:
biewlib/sysdep/_sys_dep.h:30:22: "biewlib/sysdep/"ia32"/__config.h": No such file or directory
biewlib/sysdep/_sys_dep.h:31:22: "biewlib/sysdep/"ia32"/_inlines.h": No such file or directory

So I have no solutions with new gcc-3.x branch for now.
Need some other trick.
>From other point - it's PREPROCESSOR but not C compiler which can concatenate several strings to one.
> 
> Neil.
> 
> 

Best regards! Nick