From: José Fonseca <jfons...@vmware.com>
GetCurrentThread() returns a pseudo-handle (a constant which can only
be used within the calling thread) and not a real handle.
DuplicateHandle will return a real handle, but it will create a new handle
every time we call. Calling
DuplicateHandle here means we will leak handles, which is also very bad.
In short, the Windows implementation of thrd_t needs a thorough make over.
And it won't be pretty. It looks like C11 committee over-simplified
things: it would be much better to have seperate objects for threads and
thread IDs like C++11.
For now, just comment out the thrd_current() implementation, so we get
build errors if anybody tries to use them.
Thanks to Brian Paul for spotting and diagnosing this problem.
---
include/c11/threads_win32.h | 34 ++++++++++++++++++++++++++++++++--
1 file changed, 32 insertions(+), 2 deletions(-)
diff --git a/include/c11/threads_win32.h b/include/c11/threads_win32.h
index 771db94..d4c2a72 100644
--- a/include/c11/threads_win32.h
+++ b/include/c11/threads_win32.h
@@ -492,12 +492,42 @@ thrd_create(thrd_t *thr, thrd_start_t func, void *arg)
return thrd_success;
}
+#if 0
// 7.25.5.2
static inline thrd_t
thrd_current(void)
{
- return GetCurrentThread();
+ HANDLE hCurrentThread;
+ BOOL bRet;
+
+ /* GetCurrentThread() returns a pseudo-handle, which is useless. We need
+ * to call DuplicateHandle to get a real handle. However the handle value
+ * will not match the one returned by thread_create.
+ *
+ * Other potential solutions would be:
+ * - define thrd_t as a thread Ids, but this would mean we'd need to
OpenThread for many operations
+ * - use malloc'ed memory for thrd_t. This would imply using TLS for
current thread.
+ *
+ * Neither is particularly nice.
+ *
+ * Life would be much easier if C11 threads had different abstractions for
+ * threads and thread IDs, just like C++11 threads does...
+ */
+
+ bRet = DuplicateHandle(GetCurrentProcess(), // source process (pseudo)
handle
+ GetCurrentThread(), // source (pseudo) handle
+ GetCurrentProcess(), // target process
+ &hCurrentThread, // target handle
+ 0,
+ FALSE,
+ DUPLICATE_SAME_ACCESS);
+ assert(bRet);
+ if (!bRet) {
+ hCurrentThread = GetCurrentThread();
+ }
+ return hCurrentThread;
}
+#endif
// 7.25.5.3
static inline int
@@ -511,7 +541,7 @@ thrd_detach(thrd_t thr)
static inline int
thrd_equal(thrd_t thr0, thrd_t thr1)
{
- return (thr0 == thr1);
+ return GetThreadId(thr0) == GetThreadId(thr1);
}
// 7.25.5.5
--
1.8.5.3
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