Re: Issues w/ cross-compiling

[Ralf Wildenhues]

* address@hidden wrote on Wed, Jul 09, 2008 at 09:24:46AM CEST:
> On Tue, 8 Jul 2008 22:57:24 +0200 Ralf Wildenhues wrote:
> >
> >If you have a way to actually execute code on the compile
> >system (get binfmt to execute 'elksemu $binary' should be
> >possible), then you can avoid compile-only tests and make
> >AC_COMPUTE_INT use the cheaper execution test.
> 
> Great thank you for suggestion. Yes, by using "elksemu",
> checking for the size of types would be more exact.
> Should I write elksemu-specific checking? e.g., checking
> the target is ELKS, system has "elksemu" (and it works),
> then several checks are executed by elksemu.
> If Autoconf has any existing macros to utilize such
> emulatior command, please let me know. I don't think
> such commandline emulator is popular (I guess, today
> virtual machine solution are prefered), so I don't
> hesitate to write ELKS-specific macros.

No, Autoconf unfortunately does not have the means to invoke
elksemu currently.  However, you can tell your system admin
to enable binfmt_misc support for 8086 binaries.  On my system
it works like this (as root):

   modprobe binfmt_misc
   echo ':i86-elks:M::\x01\x03\x20\x00:\xff\xff\xff\x83:/lib/elksemu:' \
        > /proc/sys/fs/binfmt_misc/register

and causes the kernel to just start elksemu when an 8086
binary is exec'ed.  That means to you, and to configure scripts,
it looks like those binaries can be executed natively, thus
the cross-compile sections of the configure script won't be used,
thus the AC_COMPILE_INT computations will be correct for this case.

Hope that helps.

FWIW, I've started working on a patch against Autoconf to support
bcc better, but it will be a bit before it's finished, because
essentially, this compiler is *really* unpredictable when compared
to, say, GCC.  bcc definitely needs some work, too.

Cheers,
Ralf