Re: [Boost-users] segfault using boost::thread_specific_ptr

21 Dec 2015

      Ah thanks. I had to change the check to if (! tls_buffer.get()) or

In file included from ./EventWorker.h:13:
./Util.h:85:13: error: invalid argument type
      'boost::thread_specific_ptrstd::stringstream' to unary expression
        if (! tls_buffer) {
            ^ ~~~~~~~~~~
1 error generated.
make: *** [EventWorker.o] Error 1

but it seems to work now.

Mike
...
On Dec 21, 2015, at 10:04 AM, Juan Ramírez  wrote:
tls_buffer is not initialized, thread_specific_ptr will not allocate memory for you (it will call delete on thread exit tough)
if (!tls_buffer) {
   tls_buffer.reset(new std::stringstream());
}
The previous must be done before any attempt to use that variable
On Mon, Dec 21, 2015 at 11:34 AM, Michael P. Soulier  wrote:
Hello,
I’m trying to implement a thread-safe logger that uses a boost::thread_specific_ptr to a std::stringstream as a logging buffer.
static boost::thread_specific_ptrstd::stringstream tls_buffer;
class MLoggerHandler
{
public:
    MLoggerHandler(boost::mutex& mutex, std::ostream& ostream);
    ~MLoggerHandler();
    void setLevel(int level);
template <class T>
    // For handling << from any object.
    MLoggerHandler& operator <<(T input) {
        std::cerr << "Adding to buffer" << std::endl;
        if (m_start) {
            *tls_buffer << localDateTime() << " " << input; <================= SEGFAULT
            m_start = false;
        }
        else {
            *tls_buffer << input;
        }
        std::cerr << "On buffer: " << tls_buffer->str() << std::endl;
        return *this;
    }
    // For handling std::endl
    std::ostream& operator <<(std::ostream& (*f)(std::ostream&)) {
        std::cerr << "Flushing buffer" << std::endl;
        m_start = true;
        std::ostream& rv = f(m_ostream);
        m_mutex.lock();
        m_ostream << tls_buffer->str();
        m_mutex.unlock();
        tls_buffer->str("");
        return rv;
    }
private:
    // A flag to indicate the beginning of a new line.
    bool m_start = true;
    // A mutex passed in from the main logger for synchronization.
    boost::mutex& m_mutex;
    // The logging level.
    int m_level;
    // The output stream.
    std::ostream& m_ostream;
    // Return the current date and time as a localized string.
    const std::string localDateTime();
};
The initial idea, was to flush the buffer and write when a terminating std::endl was encountered. But, just trying to dereference the pointer and write to the std::stringstream is crashing. Do I need to initialize the std::stringstream, or is it initialized in constructor?
Thanks,
Mike
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-- 
Juan
:wq
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