[llvm-bugs] clang-tidy weird warning for mutex lock

[Abhishek Deshpande via llvm-bugs]

Recently, I checked out llvm tools from following link.

http://llvm.org/docs/GettingStarted.html#getting-started-quickly-a-summary

I followed the instructions and build the tools required for clang-tidy.

At my workplace, we are modernizing our module's source code to C++11
standard and we aggressively using clang-tidy (built from the trunk as
mentioned above) for this purpose.

One of the use cases where we are stuck is a weird warning for mutex locks.

Here is a smaller reproducible version of our use case

#include <boost/thread.hpp>

void foo2()
{
    boost::mutex crapmutex;
    boost::mutex::scoped_lock lock(crapmutex);
}

int main() {
    foo2();
    return 0;
}

When we run clang-tidy with all checks enabled, specify our internal
compilation options followed by standard compiler flags, we get following
warnings for mutex locks

33110 warnings generated.
..../boost/include/boost/thread/pthread/mutex.hpp:149:23: warning: This
lock has already been acquired [clang-analyzer-alpha.unix.PthreadLock]
            int res = posix::pthread_mutex_lock(&m);
                      ^
..../Source.cpp:13:5: note: Calling 'foo2'
    foo2();
    ^
...../Source.cpp:8:31: note: Calling constructor for 'unique_lock'
    boost::mutex::scoped_lock lock(crapmutex);
                              ^
..../boost/include/boost/thread/lock_types.hpp:157:7: note: Calling
'unique_lock::lock'
      lock();
      ^
..../boost/include/boost/thread/lock_types.hpp:369:7: note: Taking false
branch
      if (m == 0)
      ^
..../boost/include/boost/thread/lock_types.hpp:374:7: note: Taking false
branch
      if (owns_lock())
      ^
..../boost/include/boost/thread/lock_types.hpp:379:7: note: Calling
'mutex::lock'
      m->lock();
      ^
..../boost/include/boost/thread/pthread/mutex.hpp:149:23: note: This lock
has already been acquired
            int res = posix::pthread_mutex_lock(&m);
                      ^
Suppressed 33109 warnings (33109 in non-user code).
Use -header-filter=.* to display errors from all non-system headers. Use
-system-headers to display errors from system headers as well.

Why is this warning coming up? These two locks are totally not related. Is
this a bug? If not then why is this warning coming up?

Please let me know if any more details are required.

Thanks,
Recker
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