[Bug preprocessor/66932] Preprocessor includes wrong header file

["pilot.mm at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66932

--- Comment #3 from Michael McWilliam <pilot.mm at gmail dot com> ---
(In reply to Jonathan Wakely from comment #2)
> Works for me too, with any version.
> 
> gcc_bug$ which gcc
> ~/gcc/4.9.3/bin/gcc
> gcc_bug$ cd gas
> gas$ ./compile.sh 
> ^[[3~In file included from ./../include/alloca-conf.h:2:0,
>                  from as.h:2,
>                  from as.c:2:
> ./config.h:2:2: warning: #warning "You have included the correct include
> file" [-Wcpp]
>  #warning "You have included the correct include file"
>   ^
> 
> 
> Please provide the output of: echo $CPATH $C_INCLUDE_PATH


CPATH is empty
C_INCLUDE_PATH is:

:/usr/local/atlas/include:/usr/local/atlas/include/atlas:/usr/local/atlas/include:/usr/local/atlas/include/atlas

So when I remove the leading : in C_INCLUDE_PATH and delete the duplicated
entries, magically it works. So clearly there is an error on my machine on the
way environment variables are being set... I will have to fix that...

I suppose the problem is a NULL path in the variable leads to undefined
behaviour... maybe gcc could be improved to ignore null paths or spit a warning
or something?