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

[Yann Droneaud]

[Moving the discussion to address@hidden

Hi,

I've recently sent two patches against config.sub to
address@hidden

http://lists.gnu.org/archive/html/config-patches/2013-02/msg00000.html
http://lists.gnu.org/archive/html/config-patches/2013-02/msg00001.html

Yann Droneaud (2):
      config.sub: use $name instead of $1
      config.sub: be more liberal on input case: accept upper case name

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. I was surprised by the behavor and made
patches to allow config.sub to recognize this string.

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.

Could people on the list give some advice on this subject ?

Regards.

-- 
Yann Droneaud
OPTEYA