From Thibault Genessay, "On Windows, when a process tries to spawn one too many thread,

_beginthreadex() fails but OpenThreads still waits on the startup
Block before returning to the caller of OpenThreads::Thread::start().
This causes a deadlock. The return value of _beginthreadex() is
actually checked, but after the call to OpenThreads::Block::block() so
it is basically useless.

Attached is a fix to move the check for the return value of
_beginthreadex() before the call to block(), so that start() can
return to the caller with a non-zero error code. This solves the
problem for me."

src/OpenThreads/win32/Win32Thread.cpp

@@ -345,13 +345,13 @@ int Thread::start() {
 
     pd->uniqueId = (int)ID;
 
-    // wait till the thread has actually started.
-    pd->threadStartedBlock.block();
-
     if(!pd->tid) {
         return -1;
     }
 
+    // wait till the thread has actually started.
+    pd->threadStartedBlock.block();
+
     return 0;
 
 }