address@hidden

[Peter Simons]

Hi,

I discovered an interesting problem in autoconf when used with gcc
3.x. On my machine, I have a variety of paths set in the environment
variable C_INCLUDE_PATH in order to tell gcc to search those
directories for standard includes as well. If someone specifies one of
those directories on the command line with an -I flag -- in addition
to the fact that gcc would have searched that directory anyway --, the
compiler will give the following warning:

 | cc1plus: warning: changing search order for system directory 
"/usr/X11R6/include"
 | cc1plus: warning:   as it has already been specified as a non-system 
directory

This is not really a problem, it's more an informational message.
Unfortunately, though, it will make macros like AC_TRY_CPP and friends
think that the compile process failed. Thus they assume that the
header file -- or whatever resource the user wanted to test for --
would not be available, even though it probably is.

I witnessned this problem while compiling "imlib" and was
flabbergasted to see that the configure script simply refused to find
all kinds of headers, like <jpeglib.h> and others, even though they
were clearly installed on the system.

Obviously, this is not exactly a problem in autoconf, but it surely is
a problem that will concern autoconf users, hence I thought I should
point the fact out. Maybe someone has an incredibly clever idea how to
remedy this? If, I'd certainly like to hear about it. ;-)

        -peter