Re: gcc 3.2's cpp breaks configure scripts

["John David Anglin" <dave at hiauly1 dot hia dot nrc dot ca>]

> > Turning the warning off is not the correct solution, although there
> > may be some circumstances in which it is emitted when it shouldn't
> > be.
> 
> I think so... but I am probably wrong hehe...

You can display the include search order with "gcc -v -E".  The situation
where gcc emits the message when it shouldn't is when a user include directory
is specified and it is the same as the first directory searched by gcc.
For example,

gcc -v -E main.c -I/opt/gnu/include
...
ignoring nonexistent directory "/usr/local/include"
ignoring nonexistent directory "/opt/gnu/hppa2.0w-hp-hpux11.00/include"
cpp0: warning: changing search order for system directory "/opt/gnu/include"
cpp0: warning:   as it has already been specified as a non-system directory
ignoring duplicate directory "/opt/gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /opt/gnu/include
 /opt/gnu/lib/gcc-lib/hppa2.0w-hp-hpux11.00/3.1.1/include
 /usr/include
End of search list.

As can be seen, the search order hasn't really changed.  If "-I/usr/include"
were added to the command, the search order would really have changed.

These are rules under which the macro lib-prefix.m4 used by configure
in textutils-2.1 adds include directories to CPPFLAGS:

    dnl Potentially add $additional_includedir to $CPPFLAGS.
    dnl But don't add it
    dnl   1. if it's the standard /usr/include,
    dnl   2. if it's already present in $CPPFLAGS,
    dnl   3. if it's /usr/local/include and we are using GCC on Linux,
    dnl   4. if it doesn't exist as a directory.

"/opt/gnu" is my standard prefix.  As can be seen, the above macro
will add "-I/opt/gnu/include" to CPPFLAGS and cause a gcc warning
if something interesting is found there (e.g., libintl.h).

Dave
-- 
J. David Anglin                                  dave.anglin@nrc.ca
National Research Council of Canada              (613) 990-0752 (FAX: 952-6605)