This issue doesn't seem to be the case with all of my projects, one in particular gives this issue when I run `npm i` (node v6.9.4 (npm v5.6.0) <- also not sure if this is right):

```
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__threading_support:25:11: fatal error: 
          'pthread.h' file not found
    # include <pthread.h>

```

The error log:

```
12788 verbose stack Error: farmhash@1.2.1 install: `node-gyp rebuild`
12788 verbose stack Exit status 1
12788 verbose stack     at EventEmitter.<anonymous> (/Users/tom.firth/.nvm/versions/node/v6.9.4/lib/node_modules/npm/node_modules/npm-lifecycle/index.js:285:16)
12788 verbose stack     at emitTwo (events.js:106:13)
12788 verbose stack     at EventEmitter.emit (events.js:191:7)
12788 verbose stack     at ChildProcess.<anonymous> (/Users/tom.firth/.nvm/versions/node/v6.9.4/lib/node_modules/npm/node_modules/npm-lifecycle/lib/spawn.js:55:14)
12788 verbose stack     at emitTwo (events.js:106:13)
12788 verbose stack     at ChildProcess.emit (events.js:191:7)
12788 verbose stack     at maybeClose (internal/child_process.js:877:16)
12788 verbose stack     at Process.ChildProcess._handle.onexit (internal/child_process.js:226:5)
12789 verbose pkgid farmhash@1.2.1
12790 verbose cwd /Users/tom.firth/Sites/the-works
12791 verbose Darwin 16.7.0
12792 verbose argv "/Users/tom.firth/.nvm/versions/node/v6.9.4/bin/node" "/Users/tom.firth/.nvm/versions/node/v6.9.4/bin/npm" "i"
12793 verbose node v6.9.4
12794 verbose npm  v5.6.0
12795 error code ELIFECYCLE
12796 error errno 1
12797 error farmhash@1.2.1 install: `node-gyp rebuild`
12797 error Exit status 1
12798 error Failed at the farmhash@1.2.1 install script.
12798 error This is probably not a problem with npm. There is likely additional logging output above.
12799 verbose exit [ 1, true ]

```

Both of these point to `node-gyp rebuild` - I haven't had this installed globally before, but i've tried it with and without and get the same error.

I have xcode 9.1 installed and ran:
`$ xcode-select --install`
which gives: `xcode-select: error: command line tools are already installed, use "Software Update" to install updates`

I followed the steps in: [npmjs.com/fixing-npm-permissions](https://docs.npmjs.com/getting-started/fixing-npm-permissions)

`$ gcc --version`
which gives: 

```
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 9.0.0 (clang-900.0.38)
Target: x86_64-apple-darwin16.7.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

```

`$ which gcc`
which gives:
`/usr/bin/gcc`

The `node-gyp` issue makes me think it's related to the compiler but I have reinstalled xcode and node (via brew and nodejs.org)

Any help or suggestions would be really appreciated.

**edit:**

I have tried npm 3.10.10 because 5.6.0 obviously wasn't right. This was previously installed and didn't resolve the issue.

I installed xcode 8.2.1 to replace xcode 9.1, this didn't resolve the issue.