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.. >>=20 >>=20 >> On Feb 27, 2013, at 8:57 AM, Warner Losh wrote: >>=20 >>>=20 >>> On Feb 26, 2013, at 5:35 PM, Brooks Davis wrote: >>>=20 >>>> 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. >>>=20 >>> Cool! >>>=20 >>>> The patch is untested with gcc. >>>=20 >>> I'd like to see it tested with gcc :) >>>=20 >>>> 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. >>>=20 >>> The patches I posted a few months ago had that as well... >>>=20 >>>> 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. >>>=20 >>> I think this will work, but it is kludgy. I had created a = __X=3D<prefix-path> which was prepended to ${CC}, et al, in sys.mk. It = was only defined when you set CROSS_COMPILER_PATH (or = EXTERNAL_COMPILER_PATH, I forget) during the cross building stage. It = also had the advantage of making external cross binutils available. Your = patch could fairly easily use this interface instead of having to set 3 = different variables, which will morph to 10 when you add binutil = support. >>=20 >=20 > I think something like this will have to be done for binutils given = the > way -B works, but I don't think it's workable in the general compiler > case because I want to be able to use gcc46 or a future clang33 or > similar as CC without changing the system compiler. Ideally I'd > also like to support clang's method of finding appropriate binutils > by looking first for /binutils/path/${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. >>=20 >=20 > I'm not sure what you mean by "That isn't reflected in the port". s/port/patches/ will help. Basically, I did "CC?=3D${__X}cc" when I = should have done "CC?=3D${__X}cc ${__Y}". Warner
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