[Clfs-support] [Native Compiler] Problem Cross-compiling GMP MPFR and MPC

[William Harrington]

On Fri, 14 Apr 2017 10:15:36 +0200
Michele Bucca <michele.bucca at gmail.com> wrote:

> Hello Everyone,
> 
> I'm trying to cross-compile a native host-x-host compiler with the
> musl-libc library
> 
> To do that I have to
> 
> 1) compile a cross-compiler. (Done)
> 2) Install GMP, MPFR and MPC on the cross-compiler
> 3) make a host-x-host cross-compile to make a native compiler
> 
> Now I'm stuck compiling the GMP, MPFR and MPC...
> 
> I had problems with MPFR because when I tried to compile them with the
> following configure switches
> 
> ../mpfr-3.1.4/configure --host=i486-linux-musl
> --prefix=/home/michele/tmp/musl-native-toolchain/native/i486-linux-musl/
> 
> it produced me x86_64 libraries! (My host is x86_64-linux-gnu)
> 
> So I changed the configure switch like that:
> 
> ../mpfr-3.1.4/configure --host=i486-linux-musl
> --build=x86_64-linux-gnu
> --prefix=/home/michele/tmp/musl-native-toolchain/native/i486-linux-musl/
> 
> and it compiled well..
> 
> Now I'm having problems building MPC for the same reason: the
> configure is like this:
> 
> ../mpc-1.0.3/configure --host=i486-linux-musl
> --build=x86_64-linux-gnu
> --prefix=/home/michele/tmp/musl-native-toolchain/native/i486-linux-musl/
> 
> what am I doing wrong?
> 

Hello Michele,

First you need to understand the difference between host, build, and target...

https://www.gnu.org/software/autoconf/manual/autoconf-2.65/html_node/Specifying-Target-Triplets.html

You ended up with 64bit libraries because build defaulted to your host compiler.

build and host can be the same, but build will use the toolchain you need a target when cross-compiling.

In this case, build and host is the same because are most likely using the same machine to create the cross-compiler and use that cross-compiler (example):

--build=x86_64-cross-linux-gnu
--host=x86_64-cross-linux-gnu
--target=i486-linux-musl

After the cross-toolchain is built, then you can use (example):

--host=i486-linux-musl
--build=x86_64-cross-linux-gnu

If there is any confusion, you can look at he main cross-lfs CLFS book as a guide.

Sincerely,

William