comphelper: fix MSVC hang in ThreadPool::shutdown()

Commit aa68c99d88fd7abe08c4aee5206c859a0cdba38e added some code using
std::condition_variable to comphelper.

Built with MSVC 2017, this causes many cppunittester.exe processes to
deadlock in ThreadPool::shutdown():

    maTasksChanged.notify_all();

This ultimately calls NtReleaseKeyedEvent(), which never returns.

The reason appears to be a bug in Windows 7, for which a "hotfix"[1] is
avaiable here, but it's apparently not distributed via Windows Update
so we likely can't rely on users or even developers having this installed.

However, the documentation of DllMain[2] and ExitProcess[3] indicates
that during shutdown, by the time global destructors are invoked
all threads other than the one that called ExitProcess have already
been terminated.

Returning from main() implicitly calls ExitProcess [4].

As it turns out the problem only happens for some CppUnitTests because
soffice.bin will call ThreadPool::shutdown() from Desktop::doShutdown()
while it is still safe.

[1] http://support.microsoft.com/kb/2582203
[2] https://msdn.microsoft.com/en-US/library/windows/desktop/ms682583(v=vs.85).aspx
[3] https://msdn.microsoft.com/en-us/library/windows/desktop/ms682658(v=vs.85).aspx
[4] https://blogs.msdn.microsoft.com/oldnewthing/20100827-00/?p=13023

Change-Id: I6137461ca7efe9a5fbe4f8f8478fb96de3570469
Reviewed-on: https://gerrit.libreoffice.org/35066
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Stahl <mstahl@redhat.com>

1 files changed, 11 insertions, 3 deletions

diff --git a/package/qa/cppunit/test_package.cxx b/package/qa/cppunit/test_package.cxx
index 335f490ddaba..d015e8db8d66 100644
--- a/package/qa/cppunit/test_package.cxx
+++ b/package/qa/cppunit/test_package.cxx
@@ -119,8 +119,16 @@ namespace
         uno::Reference<container::XNameAccess> xNA(xZip, uno::UNO_QUERY);
         CPPUNIT_ASSERT(xNA.is());
 
+        struct TestThreadPool
         {
-            comphelper::ThreadPool aPool(4);
+            comphelper::ThreadPool aPool;
+            TestThreadPool(sal_Int32 const i) : aPool(i) {}
+            ~TestThreadPool() { aPool.shutdown(); }
+        };
+
+        {
+            TestThreadPool aPool(4);
+            comphelper::ThreadPool & rPool(aPool.aPool);
             std::shared_ptr<comphelper::ThreadTaskTag> pTag = comphelper::ThreadPool::createThreadTaskTag();
 
             std::vector<std::vector<char>> aTestBuffers(26);
@@ -135,10 +143,10 @@ namespace
                 xNA->getByName(aName) >>= xStrm;
 
                 CPPUNIT_ASSERT(xStrm.is());
-                aPool.pushTask(new Worker(pTag, xStrm, *itBuf));
+                rPool.pushTask(new Worker(pTag, xStrm, *itBuf));
             }
 
-            aPool.waitUntilDone(pTag);
+            rPool.waitUntilDone(pTag);
 
             // Verify the streams.
             CPPUNIT_ASSERT_EQUAL(size_t(26), aTestBuffers.size());