cmd/link: darwin/386 is broken in recent macOS

[bradfitz]

Apparently the darwin/386 port has been broken for some time but we never noticed because our 386 builder only ran on macOS 10.11. But @eliasnaur did and reported it. We switched to macOS 10.14 so we see the failure:

https://build.golang.org/log/9cdaf8e7ac6aec29dd0ff0eb0db06a7d9bb6ebc5

Building Go toolchain1 using /Users/gopher/goboot.
Building Go bootstrap cmd/go (go_bootstrap) using Go toolchain1.
Building Go toolchain2 using go_bootstrap and Go toolchain1.
Building Go toolchain3 using go_bootstrap and Go toolchain2.
Building packages and commands for darwin/386.
# runtime/cgo
ld: warning: The i386 architecture is deprecated for macOS (remove from the Xcode build setting: ARCHS)
ld: warning: ignoring file /Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/lib/libpthread.tbd, missing required architecture i386 in file /Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/lib/libpthread.tbd
ld: warning: ignoring file /Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/lib/libSystem.tbd, missing required architecture i386 in file /Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/lib/libSystem.tbd
Undefined symbols for architecture i386:
  "___stack_chk_fail", referenced from:
      _x_cgo_init in _x004.o
      __cgo_sys_thread_start in _x004.o
  "___stack_chk_guard", referenced from:
      _x_cgo_init in _x004.o
      __cgo_sys_thread_start in _x004.o
  "___stderrp", referenced from:
      __cgo_sys_thread_start in _x004.o
      _x_cgo_sys_thread_create in _x005.o
      _x_cgo_thread_start in _x008.o
      __cgo_sys_thread_start in _x004.o
      _x_cgo_sys_thread_create in _x005.o
      _x_cgo_thread_start in _x008.o
      __cgo_sys_thread_start in _x004.o
      _x_cgo_sys_thread_create in _x005.o
      _x_cgo_thread_start in _x008.o
  "_abort", referenced from:
      __cgo_sys_thread_start in _x004.o
      _x_cgo_sys_thread_create in _x005.o
      _x_cgo_thread_start in _x008.o
  "_fprintf", referenced from:
      __cgo_sys_thread_start in _x004.o
      _x_cgo_sys_thread_create in _x005.o
  "_free", referenced from:
      _threadentry in _x004.o
  "_fwrite$UNIX2003", referenced from:
      _x_cgo_thread_start in _x008.o
  "_malloc", referenced from:
      _x_cgo_thread_start in _x008.o
  "_nanosleep$UNIX2003", referenced from:
      _x_cgo_sys_thread_create in _x005.o
      __cgo_try_pthread_create in _x005.o
  "_pthread_attr_destroy", referenced from:
      _x_cgo_init in _x004.o
  "_pthread_attr_getstacksize", referenced from:
      _x_cgo_init in _x004.o
      __cgo_sys_thread_start in _x004.o
  "_pthread_attr_init", referenced from:
      _x_cgo_init in _x004.o
      __cgo_sys_thread_start in _x004.o
  "_pthread_cond_broadcast", referenced from:
      _x_cgo_notify_runtime_init_done in _x005.o
  "_pthread_cond_wait$UNIX2003", referenced from:
      __cgo_wait_runtime_init_done in _x005.o
  "_pthread_create", referenced from:
      _x_cgo_sys_thread_create in _x005.o
      __cgo_try_pthread_create in _x005.o
     (maybe you meant: __cgo_try_pthread_create)
  "_pthread_detach", referenced from:
      _x_cgo_sys_thread_create in _x005.o
      __cgo_try_pthread_create in _x005.o
  "_pthread_mutex_lock", referenced from:
      __cgo_wait_runtime_init_done in _x005.o
      _x_cgo_notify_runtime_init_done in _x005.o
      _x_cgo_set_context_function in _x005.o
      __cgo_get_context_function in _x005.o
  "_pthread_mutex_unlock", referenced from:
      __cgo_wait_runtime_init_done in _x005.o
      _x_cgo_notify_runtime_init_done in _x005.o
      _x_cgo_set_context_function in _x005.o
      __cgo_get_context_function in _x005.o
  "_pthread_sigmask$UNIX2003", referenced from:
      __cgo_sys_thread_start in _x004.o
  "_setenv$UNIX2003", referenced from:
      _x_cgo_setenv in _x006.o
  "_strerror$UNIX2003", referenced from:
      __cgo_sys_thread_start in _x004.o
      _x_cgo_sys_thread_create in _x005.o
  "_unsetenv$UNIX2003", referenced from:
      _x_cgo_unsetenv in _x006.o
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)
go tool dist: FAILED: /private/var/folders/9w/4l2_g3kx01x199n37fbmv3s80000gn/T/workdir-host-darwin-10_14/go/pkg/tool/darwin_386/go_bootstrap install -gcflags=all= -ldflags=all= std cmd: exit status 2

/cc @ianlancetaylor @randall77

[ianlancetaylor]

From the error messages, the C compiler and linker no longer support 386. Unless there is some additional XCode package we can install to add support, I think we would have to change the darwin/386 port to no longer support cgo or external linking.

[eliasnaur]

FWIW, I can get much further on my macOS 10.14 with Xcode 10.2.1:

$ GOARCH=386 ./all.bash
Building Go cmd/dist using /Users/elias/go1.10.1.
Building Go toolchain1 using /Users/elias/go1.10.1.
Building Go bootstrap cmd/go (go_bootstrap) using Go toolchain1.
Building Go toolchain2 using go_bootstrap and Go toolchain1.
Building Go toolchain3 using go_bootstrap and Go toolchain2.
Building packages and commands for host, darwin/amd64.
Building packages and commands for target, darwin/386.

##### Testing packages.
ok  	archive/tar	0.126s
ok  	archive/zip	2.516s
ok  	bufio	0.291s
ok  	bytes	0.958s
ok  	compress/bzip2	0.180s
...

I don't know what is different on the builder. I have the full Xcode installed, not just the command line tools; perhaps that makes a difference?

[ianlancetaylor]

According to https://support.apple.com/en-us/HT208436, Mojave (10.14) is the last version of macOS to support running 32-bit apps.

According to https://developer.apple.com/documentation/xcode_release_notes/xcode_10_release_notes?language=objc , "The macOS 10.14 SDK no longer contains support for compiling 32-bit applications. If developers need to compile for i386, Xcode 9.4 or earlier is required. (39858111)".

[ianlancetaylor]

@eliasnaur By setting GOARCH=386 on an amd64 system, you are defaulting to CGO_ENABLED=0. That will disable cgo support, and will not use the C compiler or linker.

[eliasnaur]

Duh, thanks for clearing that up.

[bradfitz]

I think we would have to change the darwin/386 port to no longer support cgo or external linking.

SGTM. For a ~month until macOS 10.15 is out with no 386 support at all.

[gopherbot]

Change https://golang.org/cl/174497 mentions this issue: cmd/dist: disable cgo for darwin/386