On 28/03/2019 10:28, Jan Beulich wrote: >>>> On 28.03.19 at 11:14, <andrew.coop...@citrix.com> wrote: >> On 28/03/2019 09:55, Jan Beulich wrote: >>>>>> On 27.03.19 at 19:45, <julien.gr...@arm.com> wrote: >>>> Clang uses "-target" option for cross-compilation. >>> And all possible targets are always available? I'd like to point out >>> that CROSS_COMPILE can be used for other than actual cross >>> compilation, e.g. building with just an alternative tool chain >>> built for the same target. Dropping the $(CROSS_COMPILE) >>> prefixes makes this impossible afaict. Requiring suitable wrapper >>> scripts to be put in place would seem better to me. >>> >>> I also wonder why this change is needed for Arm, but wasn't >>> needed so far for x86. But perhaps no-one ever tried using it >>> so far ... >> It seems that CROSS_COMPILE is a GNU-ism, which is not shared by the >> clang world. I can't find anything which will make you a >> $FOO-$BAR-clang binary, whereas you do typically get clang-$X aliases >> for the different versions of clang. > Oh, interesting. For my own re-built tool chains I actually can't use > CROSS_COMPILE either, because traditionally all my wrapper scripts > have a suffix like you say clang uses too. I patch in > > cross-compile ?= $(CROSS_COMPILE)$(1) > > locally as a fallback, to then use it as > > AS = $(call cross-compile,as) > > and then override things in the build root directory .config to > suite my actual needs, e.g. in its simplest possible form > > cross-compile=$(1)x > > But of course this doesn't fit clang either, as it's (aiui) only the > compiler which wants to be overridden this way. > >> Using -target is from the Clang instructions on cross compilation, which >> say to do it this way. https://clang.llvm.org/docs/CrossCompilation.html >> >> The targets supported will depend on the configuration Clang was >> compiled with, but Clang specifically opposes GCC's way of requiring the >> user to recompile for every different target. It is expected that a >> packager of clang will enable all of the supported targets in the >> package they distribute. > Are you sure a distro caring about, say, only x86 would indeed > enable Arm and all sorts of other architectures in the compiler, > just because it can be enabled? IOW I assume the need for an > override to the system default clang binaries would still exist.
I've just tried, and Ubuntu 16.04's default clang-3.8 is perfectly happy compiling Aarch64, and makes a suitable looking elf object. (I can't actually disassemble it because objdump chokes, but .text is the expected length) As the cross-compilation documentation states, this is a deliberate design decision which, amongst other things, prevents distros from needing to maintain per-arch packages. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
