[libcxx-commits] [libcxx] 715ca75 - [libcxx] [test] Fix spurious failures in the thread detach test on Windows

[Martin Storsjö via libcxx-commits]

Author: Martin Storsjö
Date: 2021-07-08T12:36:03+03:00
New Revision: 715ca752ac4f8ba69fe68110823e0eabf5614bc7

URL: https://github.com/llvm/llvm-project/commit/715ca752ac4f8ba69fe68110823e0eabf5614bc7
DIFF: https://github.com/llvm/llvm-project/commit/715ca752ac4f8ba69fe68110823e0eabf5614bc7.diff

LOG: [libcxx] [test] Fix spurious failures in the thread detach test on Windows

Make sure that the detached thread has started up before exiting
the process.

If the detached thread hasn't started up at all, and the main thread
exits, global data structures in the process are torn down, which
then can cause crashes when the thread starts up late after required
mutexes have been destroyed. (In particular, the mutex used internally
in _Init_thread_header, which is used in the initialization of
__thread_local_data()::__p, can cause crashes if the main thread already
has finished and progressed far with destruction.)

Differential Revision: https://reviews.llvm.org/D105592

Added: 
    

Modified: 
    libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.member/detach.pass.cpp

Removed: 
    


################################################################################
diff  --git a/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.member/detach.pass.cpp b/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.member/detach.pass.cpp
index ea82d5392aeb6..03dc79d2d8379 100644
--- a/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.member/detach.pass.cpp
+++ b/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.member/detach.pass.cpp
@@ -60,7 +60,7 @@ class G
 int G::n_alive = 0;
 bool G::op_run = false;
 
-void foo() {}
+void foo() { done = true; }
 
 int main(int, char**)
 {
@@ -75,6 +75,7 @@ int main(int, char**)
         assert(G::n_alive == 1);
     }
     assert(G::n_alive == 0);
+    done = false;
 #ifndef TEST_HAS_NO_EXCEPTIONS
     {
         std::thread t0 = support::make_test_thread(foo);
@@ -85,6 +86,11 @@ int main(int, char**)
             t0.detach();
         } catch (std::system_error const&) {
         }
+        // Wait to make sure that the detached thread has started up.
+        // Without this, we could exit main and start destructing global
+        // resources that are needed when the thread starts up, while the
+        // detached thread would start up only later.
+        while (!done) {}
     }
 #endif