For those of us who are on macOS, you usually do not have any gcc, it’s all clang behind the curtains. E.g. see
$ /usr/bin/gcc --version Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1 Apple LLVM version 8.1.0 (clang-802.0.42) Target: x86_64-apple-darwin16.6.0 Thread model: posix InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin ld, is apples ld64 (see https://opensource.apple.com/source/ld64/) $ /usr/bin/ld -v @(#)PROGRAM:ld PROJECT:ld64-278.4 configured to support archs: armv6 armv7 armv7s arm64 i386 x86_64 x86_64h armv6m armv7k armv7m armv7em (tvOS) LTO support using: LLVM version 8.1.0, (clang-802.0.42) TAPI support using: Apple TAPI version 1.33.11 if you end up having clang+llvm-4.0.0-x86_64-apple-darwin/bin or similar in your path, you WILL have `ld.lld`, but that one is an ELF linker, which on a MachO platform won’t be very useful (and will therefore fail to link MachO objects). Llvm’s `lld` will provide you with the following semi helpful note: $ lld lld is a generic driver. Invoke ld.lld (Unix), ld (Mac) or lld-link (Windows) instead. however, my copy of clang+llvm, does only ship ld.lld, and lld-link, but not `ld`. Thus, if you end up having the llvm tools (and ld.lld) in your PATH, you will need to set `--disable-ld-override` during configure on macOS, or your ghc build will fail, because you end up trying to link MachO object files with an ELF only linker. Cheers, Moritz > On Jul 8, 2017, at 7:33 AM, Ben Gamari <[email protected]> wrote: > > Evan Laforge <[email protected]> writes: > >> On Fri, Jul 7, 2017 at 9:28 AM, Ben Gamari <[email protected]> wrote: >>> >>> In short, ./configure will now choose to use ld.gold or ld.lld if >>> available (although this can be disabled using the --disable-ld-override >>> configure flag). >> >> Just from curiosity, does this apply to OS X? Of course, gold is >> ELF-only, so it surely doesn't apply, but there's still lld. OS X >> uses clang to compile so I thought it might already use lld, but the >> 'ld -v' output looks different, and lld.llvm.org implies it's a >> replacement for OS X ld, so maybe not. But it doesn't look like GNU >> ld either, so maybe it's not affected by the BFD bug? >> >> I'll try 8.2 on OS X and see if the link time changes. > > 8.2 will prefer both gold and lld over bfd ld. However two conditions > must hold for these to be used, > > * The ld.lld/ld.gold executable must be in $PATH (or explicitly named > by passing the LD variable to configure) > > * $CC must understand the `-fuse-ld={gold,lld}` option. For (IMHO quite > silly) political reasons, gcc doesn't support `-fuse-ld=lld`. Debian > happens to patch gcc to add support but I don't know how common this > is in other distributions. > > Unfortunately, some earlier `gcc` versions didn't fail if given a > `-fuse-ld` option that they didn't understand. Sadly we have no reliable > way to detect this, so in this case we may end up passing a `-fuse-ld` > option that gcc simply ignores. > > In the case of OS X we use Apple's own home-grown linker. I'm not sure > whether/how OS X's gcc wrapper treats `-fuse-ld` (beyond that it doesn't > error if the flag is given). I also don't know whether lld is currently a > capable replacement for OS X ld. > > Cheers, > > - Ben > _______________________________________________ > ghc-devs mailing list > [email protected] > http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs _______________________________________________ ghc-devs mailing list [email protected] http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
