[lld] r192250 - Fix flaky elf/X86_64/dynlib-search.test.

[Rui Ueyama]

Author: ruiu
Date: Tue Oct  8 18:01:52 2013
New Revision: 192250

URL: http://llvm.org/viewvc/llvm-project?rev=192250&view=rev
Log:
Fix flaky elf/X86_64/dynlib-search.test.

Output to llvm::err() is not guaranteed to be thread-safe, so it needs
to be guarded with a lock.

Differential Revision: http://llvm-reviews.chandlerc.com/D1862

Modified:
    lld/trunk/lib/Driver/Driver.cpp

Modified: lld/trunk/lib/Driver/Driver.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/Driver/Driver.cpp?rev=192250&r1=192249&r2=192250&view=diff
==============================================================================
--- lld/trunk/lib/Driver/Driver.cpp (original)
+++ lld/trunk/lib/Driver/Driver.cpp Tue Oct  8 18:01:52 2013
@@ -25,6 +25,8 @@
 #include "llvm/Support/Path.h"
 #include "llvm/Support/raw_ostream.h"
 
+#include <mutex>
+
 namespace lld {
 
 /// This is where the link is actually performed.
@@ -49,13 +51,26 @@ bool Driver::link(LinkingContext &contex
   ScopedTask readTask(getDefaultDomain(), "Read Args");
   TaskGroup tg;
   int index = 0;
+  std::mutex diagnosticsMutex;
   for (auto &ie : inputGraph.inputElements()) {
     tg.spawn([&, index] {
-      if (error_code ec = ie->parse(context, diagnostics)) {
-        FileNode *fileNode = (llvm::dyn_cast<FileNode>)(ie.get());
-        diagnostics << fileNode->errStr(ec) << "\n";
+      // Writes to the same output stream is not guaranteed to be thread-safe.
+      // We buffer the diagnostics output to a separate string-backed output
+      // stream, acquire the lock, and then print it out.
+      std::string buf;
+      llvm::raw_string_ostream stream(buf);
+
+      if (error_code ec = ie->parse(context, stream)) {
+        FileNode *fileNode = llvm::dyn_cast<FileNode>(ie.get());
+        stream << fileNode->errStr(ec) << "\n";
         fail = true;
       }
+
+      stream.flush();
+      if (!buf.empty()) {
+        std::lock_guard<std::mutex> lock(diagnosticsMutex);
+        diagnostics << buf;
+      }
     });
     ++index;
   }