cmd/dist: depends on clang license being accepted on OSX

[cookieo9]

In a recent update to either the OS or the dev-tools clang on OSX will refuse to run (with error code 69) until it is run as root, and the license is accepted.

The output from ./all.bash when compiling from source is:

go tool dist: cannot invoke C compiler "clang": exit status 69

Go needs a system C compiler for use with cgo.
To set a C compiler, export CC=the-compiler.
To disable cgo, export CGO_ENABLED=0.

Which is a little of a head scratcher. I think the error message could elaborate on a possible cause, so that the users don't think the only solution is to disable cgo.

[ianlancetaylor]

It seems kind of special purpose to have cmd/dist print out a specific message about this oddity. What does clang print if you run it as non-root before root? Would it be sufficient for cmd/dist to display that output?

[cookieo9]

It prints out a message to the effect that clang needs to be run as root to accept the license (I've lost the output, so I can't give exact details.) I was just thinking that it would make sense for the build process to make it clear what the problem was. Either by outputting clang's output, or by printing a message when darwin's clang fails with a certain error code.

[rakyll]

It prints out

Agreeing to the Xcode/iOS license requires admin privileges, please re-run as root via sudo.

As an experienced user, I knew what I had to do. But it is confusing for anyone who doesn't know they need to run clang, accept the license and so on.

[rakyll]

/cc @crawshaw @hyangah

This error message is also visible from gomobile build's output without any useful context.

gomobile  build  -target=android .
gomobile: xcrun --find: exit status 69


Agreeing to the Xcode/iOS license requires admin privileges, please re-run as root via sudo.

[rsc]

It's wacky but I think we probably do need to special case it. OS X is a very common platform for our users, and this is a very common situation. Printing the compiler output is not enough unless we make it very clear that it's compiler output and that the user is not being asked to sudo ./all.bash (which would work but isn't what we want).

[bradfitz]

On a fresh Capitan (10.11.1 (15B42)) install, I see:

ward5k:~ bradfitz$ git
xcode-select: note: no developer tools were found at '/Applications/Xcode.app', requesting install. Choose an option in the dialog to download the command line developer tools.
ward5k:~ bradfitz$ echo $?
1
ward5k:~ bradfitz$ clang
xcode-select: note: no developer tools were found at '/Applications/Xcode.app', requesting install. Choose an option in the dialog to download the command line developer tools.
ward5k:~ bradfitz$ echo $?
1

[rsc]

@bradfitz That must be before you installed Xcode. After you install Xcode then you get the message about re-running as root.

[gopherbot]

CL https://golang.org/cl/17940 mentions this issue.