Date: Wed, 17 Nov 2010 16:32:18 -0700 From: Warner Losh <imp@bsdimp.com> To: John Baldwin <jhb@freebsd.org> Cc: Garrett Cooper <gcooper@freebsd.org>, Warner Losh <imp@freebsd.org>, Tijl Coosemans <tijl@coosemans.org>, Dimitry Andric <dim@freebsd.org>, freebsd-arch@freebsd.org Subject: Re: Support for cc -m32 Message-ID: <4CE46602.9000303@bsdimp.com> In-Reply-To: <201011171718.37798.jhb@freebsd.org> References: <201007291718.12687.tijl@coosemans.org> <4CE417B3.3030102@bsdimp.com> <201011172058.05683.tijl@coosemans.org> <201011171718.37798.jhb@freebsd.org>
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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.
Warner
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