Re: Need for --build with --host when cross-compiling ?

[Jan Engelhardt]

On Sunday 2013-02-03 10:49, Yann Droneaud wrote:
>
>I tried to explain the reasonning behind those patches in the following
>thread:
>http://lists.gnu.org/archive/html/config-patches/2013-02/msg00002.html
>
>Those patches are to be used as part of a kind of a workaround for the
>need to give a --build option when using --host option as part of a
>cross-compilation.
>
>When running ./configure --host=<triplet>, I'm getting
>
>configure: WARNING: if you wanted to set the --build type, don't use
>--host.
>    If a cross compiler is detected then cross compile mode will be used
>
>It's explain in: 14.1 Specifying target triplets
>
>"For historical reasons, whenever you specify `--host', be sure to
>specify `--build too'; this will be fixed in the future. So, to enter
>cross-compilation mode, use a command like this"
>
>http://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.69/html_node/Specifying-Target-Triplets.html#Specifying-Target-Triplets
>
>So to create a "valid" --build argument, I was going to use
>--build=`uname -p`-`uname -s` but its producing 'x86_64-Linux' which is
>not recognized by config.sub.

 --build/--host/--target is not supposed to be fed any names besides those
in the config.sub "dictionary". Toolchain names that do not follow suit
are not usable, and that currently includes, for example, x32 support.

>Even if I think config.sub should be more liberal in its input, autoconf
>and ./configure script should probably be fixed to not require a --build
>option when cross-compiling.

The --build flag is not required. If it were, you would get an ERROR
instead of a WARNING.