Header directories order and gnulib problem

[Michael Goffioul]

Hi,

I got a problem with header dirs order and gnulib with my setup (based on MSVC).
This is mostly due to my specific setup, but as this kind of problem can happen,
I thought I could report it.

The problem is in liboctave compilation (at least). The compilation command
contained some -I components *before* the regular -I../libgnu. If one of those
dir happen to provide one of the gnulib headers, the former will be picked up
instead of the expected gnulib one. By scanning config.log, I could detect that
this -I component is coming from 'pcre-config --cflags' which is used
to populate
CPPFLAGS.

In my case, 'pcre-config --cflags' returns
'-IC:/Software/VC9Libs/include', which
happen to contain also unistd.h. So when compiling liboctave, the unistd.h
version of gnulib is not picked up, leading to undefined identifiers.

Michael.