Memory leak fix for Managed Static Mutex

[paigeale]

Summary

When llvm exists inside of a dll and one links to the LLVM libraries there exists a memory leak on the unload of the dll because the mutex inside of the ManagedStatic class does not get released.

[hliao]

could you keep the original scoped lock by adding a level of block?

[paigeale]

Updated diff to keep original lock mechanism

[paigeale]

@hliao ,

Could you please review latest change and merge if satisfactory?

[hliao]

Could you double-check that on other platforms? Like Linux with shared library builds. At least, there are crash in my local build.

[hliao]

that change results in regression test crashing on Linux builds.

llvm/lib/Support/ManagedStatic.cpp

 
 /// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
 void llvm::llvm_shutdown() {
-  std::lock_guard<std::recursive_mutex> Lock(*getManagedStaticMutex());
+  {
+    std::lock_guard<std::recursive_mutex> Lock(*getManagedStaticMutex());
+
+    while (StaticList)
+      StaticList->destroy();
+  }
 
-  while (StaticList)
-    StaticList->destroy();
+  delete ManagedStaticMutex;
+  ManagedStaticMutex = nullptr;
 }