[Bug bootstrap/49502] Unable to build gcc with gmp/mpc/mpfr in its tree and flag "--enable-cxx"

["redi at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49502

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |RESOLVED
         Resolution|                            |INVALID

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-06-23 19:40:42 UTC ---
(In reply to comment #4)
> When compiling the GMP library, do not forget to enable the C++ interface:

When compiling *GMP* not when compiling GCC.

> add --enable-cxx to the configuration options." "$LINENO" 5
>   fi
> fi
> 
> Now, apparently, as I separate the output of the compilation in a special
> "objdir" directory, gmpxx.h can't be found with the paths in objdir/gmp/
> because only gmp.h and mp.h are placed there. gmpxx.h is copied later from the
> source directory by gmp with the "make install" command.

Are you trying to build ppl and cloog in-tree? that doesn't work, notice that
the prerequisites page says you can put gmp, mpfr and mpc in-tree, but not ppl
and cloog:
http://gcc.gnu.org/install/prerequisites.html

To build ppl you need GMP already installed, with C++ support.

If you build GCC with GMP in-tree, you don't get GMP installed, it's just
linked into GCC.

So of course PPL finds the system gmpxx.h because that's the only one you have
installed.


> I should write also that this script didn't mention the absence of gmpxx.h in
> objdir when a system version of gmp was already installed, for instance in
> /usr/local/lib & /usr/local/include. Ominous, no?
> 
> That being said. I'll keep away from PPL and Cloog as you suggests... ^o^ ...
> until I know more my way in gcc.

I think that's best.

> (--enable-cxx is indeed referenced in the pdf manual of gmp, p.6)

Of course, it's a GMP configure option. It's not a valid GCC one, thus this PR
is invalid.