Help building a 32bit GCC that can generate 32/64bit (x86)

[Ian Lance Taylor]

Paul Smith <paul@mad-scientist.net> writes:

>> I think the simplest way to do this would be to configure as usual on a
>> 64-bit system, and build it using something like
>>     make BOOT_CFLAGS="-m32 -g -O2"
>
> I tried to build on a 64bit system setting CC="gcc -m32" and CXX="g++
> -m32" when running configure.  But this failed.  I'll look up
> BOOT_CFLAGS and see what I can find out.

Setting CC and CXX won't help, because that won't affect the later
bootstrap stages.  Setting BOOT_CFLAGS should affect the way the later
bootstrap stages are built, and should cause them to build 32-bit
binaries.  I haven't actually tried it.

> One, build on a 32bit host and use --target=x86_64-pc-linux-gnu (or
> something) to get a 64bit cross compiler (I assume(?) the resulting
> compiler will also be able to build 32bit targets).

That should work.

> Two, build on a 64bit host and figure out a way to force the resulting
> compiler to be a 32bit application.  Would the best way of doing that be
> using configure with CC="gcc -m32"?  Or setting --host=i686-pc-linux-gnu
> (or similar)?  Or...?

That should work, but use BOOT_CFLAGS as I suggested.

>> > I am using --enable-targets=all to configure.
>> 
>> That only affects the binutils.
>
> It's listed in the GCC install.info file... is it relevant only for
> binutils?

I'm sorry, you're quite right.  I did not know about that.  You're
right, using --enable-targets=all when bootstrapping on a 32-bit ought
to give you a compiler which supports the -m64 option.  What failed when
you tried that?

Ian