Compiling as 32bit on MacOSX

[Gregory Ewing]

Ned Deily wrote:
> Perhaps you're 
> calling ld(1) directly?  To link multiple-arch executables (etc), the 
> Apple gcc driver does the dirty work of calling ld multiple times and 
> lipo-ing the results.

Is this something that only works at link time, then? The
gcc man page says:

   "Multiple options work, and
   direct the compiler to produce "universal" binaries including
   object code for each architecture specified with -arch."

 From this I was hoping to be able to do

    gcc -arch i386 -arch x86_64 -c foo.c

and get dual-architecture .o files that could then be linked
into dual-architecture libraries. But if I do the above, I
just get an x86_64 .o file.

Are you saying that I need to compile separate sets of .o
files and then combine them at link time? That sounds like
an awkward thing to retrofit onto a library's existing
build system.

-- 
Greg