On 03/03/2014 02:41 PM, jfons...@vmware.com wrote:
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.
Can you fix the word wrapping in that paragraph?
Otherwise, the series LGTM. Reviewed-by: Brian Paul <bri...@vmware.com>
And these could probably go into the next stable release(s):
Cc: "10.0" "10.1" <mesa-sta...@lists.freedesktop.org>
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
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