Date: Wed, 27 Feb 2013 14:01:42 -0700 From: Warner Losh <imp@bsdimp.com> To: Brooks Davis <brooks@FreeBSD.org> Cc: freebsd-arch@FreeBSD.org Subject: Re: [RFC] external compiler support Message-ID: <13FB8CB0-9937-4BD8-AE89-0D24494D8663@bsdimp.com> In-Reply-To: <20130227190804.GB17489@lor.one-eyed-alien.net> References: <20130227003517.GB7348@lor.one-eyed-alien.net> <28404C12-67F3-44F0-AB28-02B749472873@bsdimp.com> <51BB3E17-128A-4989-B272-D8B40D4B854B@bsdimp.com> <20130227190804.GB17489@lor.one-eyed-alien.net>
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On Feb 27, 2013, at 12:08 PM, Brooks Davis wrote: > On Wed, Feb 27, 2013 at 09:08:05AM -0700, Warner Losh wrote: >> Ooops, forgot to add one item.. >> >> >> On Feb 27, 2013, at 8:57 AM, Warner Losh wrote: >> >>> >>> On Feb 26, 2013, at 5:35 PM, Brooks Davis wrote: >>> >>>> Below (and at http://people.freebsd.org/~brooks/patches/xcc.diff) you >>>> can find an initial patch with proposed commit for external compiler >>>> support. It relies on the existing cross binutils as I'm finding that >>>> the two are fairly separable. With this patch I've been able to build >>>> from amd64 to arm, amd64, and i386 using clang from the lang/clang-devel >>>> port. I've also compiled the tree with a customized clang being >>>> developed at the University of Cambridge. >>> >>> Cool! >>> >>>> The patch is untested with gcc. >>> >>> I'd like to see it tested with gcc :) >>> >>>> Does this seem like a reasonable approach? I do plan to look at external >>>> binutils support, but it's not on the critical path for our current work >>>> so I've opted to avoid it for now. >>> >>> The patches I posted a few months ago had that as well... >>> >>>> As a bonus for those who don't need an external compiler, but do run >>>> make buildworld frequently, the XCC, XCXX, and XCPP variables can be set >>>> to the location of the installed base system compiler to avoid building >>>> the compiler twice during buildworld. >>> >>> I think this will work, but it is kludgy. I had created a __X=<prefix-path> which was prepended to ${CC}, et al, in sys.mk. It was only defined when you set CROSS_COMPILER_PATH (or EXTERNAL_COMPILER_PATH, I forget) during the cross building stage. It also had the advantage of making external cross binutils available. Your patch could fairly easily use this interface instead of having to set 3 different variables, which will morph to 10 when you add binutil support. >> > > I think something like this will have to be done for binutils given the > way -B works, but I don't think it's workable in the general compiler > case because I want to be able to use gcc46 or a future clang33 or > similar as CC without changing the system compiler. Ideally I'd > also like to support clang's method of finding appropriate binutils > by looking first for /binutils/path/${TARGET_TRIPLE}-tool and then > /binutils/path/tool. I didn't know that clang did this, but that's certainly doable. > As a strawman, let's say we add a CROSS_COMPILER_PATH and a > CROSS_BINUTILS_PATH. The former will set XCC, XCXX, and XCPP if they > are unset. The latter will control -B and set the various binutils > variables (XNM, XLD, etc). I'm not sure I like splitting things like that. It is unnatural. > The sys.mk solution seems clean at first glance, but I don't think it's > sufficently general. It's also insufficient because you need --sysroot > unless you want to build a sysroot somewhere and hardcode paths to it > into your toolchain. Worse, if you want rescue to work, --sysroot must > be part of CC etc because crunchgen doesn't make it easy to manipulate > CFLAGS. Yes, that's a hole in the current system. My stuff works great for xdev-build toolchains, but less well for generic toolchains because of the sysroot issue. that's one part of your patch I especially liked. >> I've also started looking into using clang --mumble to doing cross builds too, so I don't have to have 4 compilers configured and laying around for the different platforms I play with. That isn't reflected in the port. >> > > I'm not sure what you mean by "That isn't reflected in the port". s/port/patches/ will help. Basically, I did "CC?=${__X}cc" when I should have done "CC?=${__X}cc ${__Y}". Warner
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