Support for cc -m32

[John Baldwin]

On Wednesday, November 17, 2010 6:52:40 pm Nathan Whitehorn wrote:
> 
> On Nov 17, 2010, at 5:32 PM, Warner Losh wrote:
> 
> > On 11/17/2010 15:18, John Baldwin wrote:
> >> On Wednesday, November 17, 2010 2:57:51 pm Tijl Coosemans wrote:
> >>> cc-m32-3.diff:
> >>>     Modify amd64 headers to include i386 headers when compiling 32  
> >>> bit code.
> >>>
> >>>     All amd64 headers follow the following format:
> >>>
> >>>     #ifndef _AMD64_HEADER_H_
> >>>     #define _AMD64_HEADER_H_
> >>>
> >>>     #ifdef __i386__
> >>>     #include<i386/header.h>
> >>>     #else
> >>>
> >>>     /* Amd64 declarations go here. */
> >>>
> >>>     #endif /* __i386__ */
> >>>     #endif /* !_AMD64_HEADER_H_ */
> >> I find this to be really ugly, and error prone (since it is a  
> >> manual process).
> >> I'd prefer something that autogenerated headers in /usr/include/ 
> >> machine that
> >> #include the appropriate version similar to what Warner suggested.
> >>
> >> However, one issue with that approach (and this one) are headers  
> >> that only
> >> exist for one platform.  The end result would be that that header  
> >> would now
> >> exist for both platforms (in that if you do 'if [ -r
> >> /usr/include/machine/foo.h ]' it will be true).  We can make it  
> >> #error or
> >> otherwise fail (by including a non-existing file for example), but  
> >> if there
> >> was some way to have cc -m32 "magically" substitute "i386/" for  
> >> "machine",
> >> that is what I would most prefer.  (This has problems too in that  
> >> #include
> >> <machine/foo.h>  would work with -m32 even though /usr/include/ 
> >> machine/foo.h
> >> doesn't exist, but /usr/include/i386/foo.h does.
> > "magically" converting machine -> i386 requires cpp hacking.
> >
> > However, the if [] test is beyond the scope of the API that we  
> > support.  Scripts that use -m32 will have to cope with other issues.
> >
> > We could 'solve' this by having an /usr/include32, but even that  
> > still isn't complete.
> >
> > I contend that the least bad solution is to auto generate the  
> > machine directory from the sys/{i386,amd64}/include.  If we do that,  
> > we could implement -m64 on i386 too, but that needs a lot more  
> > infrastructure.
> 
> The other way of solving this, which continues to work very well on  
> powerpc64, is to have the machine/ stuff be identical for the two  
> platforms (which, as far as I can tell, really are the same platform,  
> but with a different ABI) and to use appropriate #ifdefs to select the  
> right things. I would imagine, based on the continued exodus of these  
> headers to x86/ anyway, that the differences are not enormously large.  
> They certainly were not for PPC.

Only a few of the headers have moved to x86/, and those were the easy
cases.  There are a few more that could be merged (or possibly have
common bits in an x86/foo.h that both versions include).

-- 
John Baldwin