gcc 7.3 bootstrap: ld is skipping incompatible mpc/mpfr/gmp libs

[Jonathan Wakely]

On 20 March 2018 at 16:20, Michael Brunnbauer wrote:
>
> hi all,
>
> I'm trying to build gcc 7.3 on an x86 32 bit system with support for 32
> and 64 bit binaries

I don't know if that's even possible, other than by building a
cross-compiler with --target=x86_64-pc-linux-gnu. Maybe it is.


> and get linking problems with mpc/mpfr/gmp during the
> bootstrap process, e.g.:
>
>  ld: skipping incompatible /usr/lib/libgmp.so when searching for -lgmp
>  ld: skipping incompatible /usr/lib/libgmp.a when searching for -lgmp
>
> I first had gmp-5.0.1/mpc-0.8.1/mpfr-2.4.2 and switched to gmp-6.1.2/mpc-1.1.0/
> mpfr-4.0.1 without success. The version is probably not the problem because
> this is ld complaining - as if libgmp had the wrong architecture.

Yes, that's what the error usually means.

> Do I need
> the libraries in a 64 bit version also for a proper bootstrap?

Probably "instead" not "also".

Have you tried the following the instructions at
https://gcc.gnu.org/wiki/InstallingGCC and using the
contrib/download_prerequisites script so that gmp/mpfr/mpc are built
as part of the build process? GCC should build them with whatever
architecture is needed.