Repair thread-unsafe modifications of n_alive in F.pass.cpp

In this example, the ctor of G runs in the main thread in the expression G(), and also in the copy ctor of G() in the DECAY_COPY inside std::thread. The main thread destroys the G() instance at the semicolon, and the started thread destroys the G() after it returns. Thus there is a race between the threads on the n_alive variable.

The fix is to join with the background thread before attempting to destroy the G in the main thread.

llvm-svn: 344820

1 files changed, 10 insertions, 4 deletions

diff --git a/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.constr/F.pass.cpp b/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.constr/F.pass.cpp
index d419b8cc855..be3fc9c5d1e 100644
--- a/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.constr/F.pass.cpp
+++ b/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.constr/F.pass.cpp
@@ -157,8 +157,11 @@ int main()
     {
         assert(G::n_alive == 0);
         assert(!G::op_run);
-        std::thread t((G()));
-        t.join();
+        {
+            G g;
+            std::thread t(g);
+            t.join();
+        }
         assert(G::n_alive == 0);
         assert(G::op_run);
     }
@@ -185,8 +188,11 @@ int main()
     {
         assert(G::n_alive == 0);
         assert(!G::op_run);
-        std::thread t(G(), 5, 5.5);
-        t.join();
+        {
+            G g;
+            std::thread t(g, 5, 5.5);
+            t.join();
+        }
         assert(G::n_alive == 0);
         assert(G::op_run);
     }