What include search path is GCC using?

["Glenn Farrow" <ghf at mailandnews dot com>]

I have downloaded libstdc++-2.90.8 and successfully rebuilt gcc-2.95.2 to
use this version of the library.  Some simple test programs compile and run
all right but the testsuite fails miserably, passing only a few of the 68
odd tests.  I am running SUSE 6.4 with kernel 2.2.14.

After a little investigation I tracked the problem down to the fact that the
testsuites were being compiled with "-I/usr/include/g++-v3".  When this flag
is specified there are a ton of parse errors in
"usr/local/include/g++-v3/bits/ios_base.h".  If I modify the testsuite to
remove this flag then I don't get the parse errors and the number of tests
that pass jumps up to 58 out of 68.

From the libstdc++ installation instructions:

"If you're building GCC from scratch, you can do the usual 'make bootstrap'
here, and libstdc++-v3 will be built as its default C++ library. The
generated g++ will magically use the correct headers, link against the
correct library binary, and in general using libstdc++-v3 will be a piece of
cake. You're done; run 'make install' (the GCC Installation instructions) to
put the new compiler and libraries into place. "

From the fact that "-I/usr/include/g++-v3" causes the testsuite to fail
miserably it would appear that this directory is not the include directory
that g++ is using by default.

1.) How can I find out the path that g++ is using by default for include
directories?

2.) If not  "-I/usr/include/g++-v3" where exactly should it be looking first
for standard C++ include files?

Thanks,
Glenn