title: Code Coverage Data Generation Failed for Swift 3.0
body: <p>I am testing a library project; the tests passed with this error message:</p>
  
  <pre><code>Aggregation tool
  '/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/llvm-profdata'
  failed with exit code 1
  </code></pre>
  
  <p>I am not using the default toolchain (Swift 2.2) but the latest snapshot.
  I switched my toolchain in Xcode preference and it builds and runs the
  tests successfully; it just does not generate code coverage data. I
  noticed that the <a href="http://llvm.org/docs/CommandGuide/llvm-profdata.html" rel="nofollow"><code>llvm-profdata</code></a> belongs to the default
  toolchain, but I did not find any <code>llvm-profdata</code> in the corresponding
  folder of the Swift 3.0 toolchain.</p>
  
  <p>Environment:</p>
  
  <ul>
  <li>OS X 10.11.5 (latest)</li>
  <li>Xcode 7.3.1 (latest)</li>
  <li>Swift June 6, 2016: LLVM cb08d1dbbd, Clang 383859a9c4, Swift
  9e8266aaeb (latest)</li>
  </ul>
  
  <p>I am not familiar with the Swift toolchain; how can I get more
  information about why <code>llvm-profdata</code> failed, possibly with Xcode command
  line tools? Or is this a bug in the current version of Swift?</p>
  
  <p>Note:</p>
  
  <ul>
  <li><p>Xcode gives me the error only for Swift 3.0; I manually checked</p>
  
  <pre><code>Build/Intermediates/CodeCoverage/Coverage.profdata
  </code></pre>
  
  <p>in build folder with <code>llvm-profdata show</code>, and it is empty only when
  I compile with Swift 3.</p></li>
  </ul>