From a61d859519d520b849c11ad5c1c1972870abd956 Mon Sep 17 00:00:00 2001 From: José Fonseca Date: Mon, 3 Mar 2014 15:06:19 +0000 Subject: c11/threads: Don't implement thrd_current on Windows. GetCurrentThread() returns a pseudo-handle (a constant which only makes sense when 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 can cause serious problems. 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 does. For now, just comment out the thrd_current() implementation, so we get build errors if anybody tries to use it. Thanks to Brian Paul for spotting and diagnosing this problem. Cc: "10.0" "10.1" Reviewed-by: Brian Paul --- include/c11/threads_win32.h | 34 ++++++++++++++++++++++++++++++++-- 1 file changed, 32 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/c11/threads_win32.h b/include/c11/threads_win32.h index 771db9460f..d4c2a72d27 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 -- cgit v1.2.3