boost thread compiler error with GCC

Question

Hello all,

on linux, gcc 4.3, compiling a class with boost::thread implementation and mutexes / condition variables I get the following strange error, apparently due to type conflicts with the posix thread library:

*Compiling: filter.cpp
/usr/include/boost/thread/condition.hpp: In member function »void boost::condition::wait(L&) [with L = boost::mutex]«:
/host/.../filter.cpp:68:   instantiated from here
/usr/include/boost/thread/condition.hpp:90: Error: no match für »operator!« in »!lock«*
*/usr/include/boost/thread/condition.hpp:90: Notice: candidates are: operator!(bool) <built in>*
*/usr/include/boost/thread/mutex.hpp:66: Error: »pthread_mutex_t boost::mutex::m_mutex« is private
/usr/include/boost/thread/condition.hpp:93: Error: in this context*

The code is:

void CFilter::process( CData **s )
{
    boost::mutex::scoped_lock bufferLock(m_mutex);
    while (!m_bStop)
        m_change.wait(bufferLock);                      //<- line 68

    // ... further processing
}

with the class declaration

#include <boost/shared_ptr.hpp>
#include <boost/bind.hpp>
#include <boost/thread/condition.hpp>
#include <boost/thread/thread.hpp>
#include <boost/thread/mutex.hpp>

class CFilter
{
    // ...
    boost::shared_ptr<boost::thread> m_thread;
    boost::mutex m_mutex;
    boost::condition m_change;
    // ...

    process( CData **s );
}

The operator error takes place in boost's condition.hpp, in

if (!lock)
    throw lock_error();

I'm using Boost 1.38.0, on Windows I don't find any problems. Any help is appreciated!

Answer 1

You must wait on the bufferLock, not m_mutex:

while (!m_bStop)
    m_change.wait(bufferLock);

Condition<>::wait() takes a ScopedLock as parameter, not a Mutex.

Cheers, V.