gcc messing up -include directive for g++?

[Sean McNeil]

Hello All,

I'm trying to compile the cvs repository of GCC and I found the
following:

I include a directive that is passed on throughout the compilation
process...

  -include hack.h

When I get to the testsuite for libstdc++, g++ changes this to

  -include -xc++-header hack.h

I see where it is happening, but I cannot see why it gets there for a
directive that has an argument (-include).

Any help would be appreciated.

Thanks,
Sean