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boostorg / thread

Boost.org thread module
http://boost.org/libs/thread
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testable_mutex is broken #313

Open Lastique opened 4 years ago

Lastique commented 4 years ago

Currently, testable_mutex fails to compile because of this static assert:

../../../boost/thread/testable_mutex.hpp:39:24:   required from here
../../../boost/atomic/detail/atomic_template.hpp:1097:83: error: static assertion failed: boost::atomic<T> requires T to be a trivially copyable type

The problem is that testable_mutex uses atomic<thread::id> internally, and thread::id is indeed not trivially copyable. The trivially copyable requirement has always been there, but it was not enforced by Boost.Atomic until not long ago. Before, the code would compile, but user-defined copy constructor would not be called, which means thread::id could cause leak of thread_data if it used a smart pointer inside.

Lastique commented 4 years ago

Since https://github.com/boostorg/thread/pull/310 was merged, the problem is somewhat reduced as thread::id is trivially copyable, unless it uses thread_data_ptr internally (when BOOST_THREAD_PROVIDES_BASIC_THREAD_ID is not defined). Also, if thread::id stores pthread_t internally, it may be too large for lock-free atomic implementation.