gcc -m32 option on amd64.

[Tom Evans]

On Fri, 2007-07-27 at 20:20 +1000, Peter Jeremy wrote:
> On 2007-Jul-27 15:13:48 +0530, Sharad Chandra <sharadc at niksun.com> wrote:
> >I am trying gcc -m32 on freebsd 6.1 amd64 env, but it does not seems to be 
> >working. i also installed /usr/port/lang/linux-libgcc/ but did not help
> >what i did is=>
> >echo "main () {}" > t.c; gcc -m32 t.c
> >/usr/bin/ld: skipping 
> >incompatible /usr/local/lib/gcc/x86_64-portbld-freebsd6.1/4.2.0/gcc/x86_64-portbld-freebsd6.1/4.2.0/libgcc.a 
> >when searching for -lgcc
> >/usr/bin/ld: cannot find -lgcc
> >collect2: ld returned 1 exit status
> >
> >how can we make this working?
> 
> You are using gcc 4.2 from ports.  I suspect this only includes the
> 64-bit libraries.  gcc in the base system includes both 32-bit and
> 64-bit libraries by default but it still suffers the same problem.
> 
> I had a go at fixing the problem in amd64/112215 but this has other
> problems and needs more work.  Note that non-trivial code will break
> because <machine/XXXX.h> points at amd64 headers whilst the -m32
> compiler needs i386 headers in many cases.  There's a non-trivial
> amount of work needed to actually get cross-building working.  I
> suggest you look throught the FreeBSD-amd64 archives.
> 

gcc on amd64 is capable of generating i386 code, but ld on amd64 is
incapable of linking i386 code together without serious amounts of work.

At work, we use a large number of amd64 boxes as compile farm servers
for i386 development, using distcc and a wrapper to invoke gcc correctly
on the external boxes.

To verify that it works (it compiles to i386 code), do this:
$ uname -a; echo "main() { } " > t.c ; gcc -c -m32 -o t.o t.c; file t.o
FreeBSD chef.mintel.co.uk 6.1-STABLE FreeBSD 6.1-STABLE #1: Fri Jun 23
12:48:28 BST 2006
operator at chef.mintel.co.uk:/usr/obj/usr/src/sys/CHEF  amd64
t.o: ELF 32-bit LSB relocatable, Intel 80386, version 1 (FreeBSD), not
stripped

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