Using WSL2 to cross-compile from Linux to Windows

[Niels Möller]

johanneskauffmann at hotmail.com writes:

> A while back someone messaged about cross-compiling from Linux to Windows [1].
> That person had a problem with the GMP script detecting the wrong build
> compiler:

It looks like that particular message ([1]
https://gmplib.org/list-archives/gmp-bugs/2020-January/004715.html) was
mine.

> Below, I implemented the patch suggested in the referenced message, and it works
> wonderfully.
>
>
> diff -r 58bb9b017366 acinclude.m4
> --- a/acinclude.m4      Sun May 29 18:08:56 2022 +0200
> +++ b/acinclude.m4      Sun Jun 12 23:34:56 2022 +0200
> @@ -3794,11 +3794,15 @@
>     [CC_FOR_BUILD=$HOST_CC],
>     [AC_MSG_ERROR([Specified HOST_CC doesn't seem to work])])
> else
> -  for i in "$CC" "$CC $CFLAGS $CPPFLAGS" cc gcc c89 c99; do
> -    GMP_PROG_CC_FOR_BUILD_WORKS($i,
> -      [CC_FOR_BUILD=$i
> -       break])
> -  done
> +  if test $cross_compiling = no ; then
> +    CC_FOR_BUILD="$CC"
> +  else
> +    for i in cc gcc c89 c99; do
> +      GMP_PROG_CC_FOR_BUILD_WORKS($i,
> +        [CC_FOR_BUILD=$i
> +         break])
> +    done
> +  fi
>    if test -z "$CC_FOR_BUILD"; then
>     AC_MSG_ERROR([Cannot find a build system compiler])
>    fi

Still makes sense to me. Could perhaps keep $CC at the *end* of the list?

I'm a bit annoyed by the related problem, that it is not enough to pass
--host to get cross_compilation set properly. For some backwards
compatiblity reasons one has to explicitly pass --build as well, even
when config.guess figures out the build system type perfectly right.
Documented in some detail at
https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.71/autoconf.html#Hosts-and-Cross_002dCompilation

Regards,
/Niels

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