test: add duplicate symbol test

On OSX symbols are exported by default, and they overlap if two
different copies of the same symbol appear in a process. This change
ensures that, on OSX, symbols are hidden by default.

Re: nodejs/node-addon-api#456

addon.gypi

@@ -90,10 +90,16 @@
 
     'conditions': [
       [ 'OS=="mac"', {
+        'cflags': [
+          '-fvisibility=hidden'
+        ],
         'defines': [
           '_DARWIN_USE_64_BIT_INODE=1'
         ],
         'xcode_settings': {
+          'OTHER_CFLAGS': [
+            '-fvisibility=hidden'
+          ],
           'DYLIB_INSTALL_NAME_BASE': '@rpath'
         },
       }],

test/test-addon.js

@@ -19,6 +19,18 @@ function runHello(hostProcess) {
   return execFileSync(hostProcess, ['-e', testCode], { cwd: __dirname }).toString()
 }
 
+function runDuplicateBindings(hostProcess) {
+  if (!hostProcess) {
+    hostProcess = process.execPath
+  }
+  var testCode =
+    "console.log((function(bindings) {" +
+    "return bindings.pointerCheck1(bindings.pointerCheck2());" +
+    "})(require('duplicate_symbols')))"
+  console.log('running ', hostProcess);
+  return execFileSync(hostProcess, ['-e', testCode], { cwd: __dirname }).toString()
+}
+
 function getEncoding() {
   var code = 'import locale;print locale.getdefaultlocale()[1]'
   return execFileSync('python', ['-c', code]).toString().trim()
@@ -52,6 +64,23 @@ test('build simple addon', function (t) {
   proc.stderr.setEncoding('utf-8')
 })
 
+test('make sure addon symbols do not overlap', function (t) {
+  t.plan(3)
+
+  var addonPath = path.resolve(__dirname, 'node_modules', 'duplicate_symbols')
+  // Set the loglevel otherwise the output disappears when run via 'npm test'
+  var cmd = [nodeGyp, 'rebuild', '-C', addonPath, '--loglevel=verbose']
+  var proc = execFile(process.execPath, cmd, function (err, stdout, stderr) {
+    var logLines = stderr.toString().trim().split(/\r?\n/)
+    var lastLine = logLines[logLines.length-1]
+    t.strictEqual(err, null)
+    t.strictEqual(lastLine, 'gyp info ok', 'should end in ok')
+    t.strictEqual(runDuplicateBindings().trim(), 'not equal')
+  })
+  proc.stdout.setEncoding('utf-8')
+  proc.stderr.setEncoding('utf-8')
+})
+
 test('build simple addon in path with non-ascii characters', function (t) {
   t.plan(1)