c++ - pipe and stringstream - memory leak when writing in the stringstream -

i have memory issue code when try write binary data in stringstream object. valgrind log (first spotted system monitor):

==23562== 16,368 bytes in 1 blocks possibly lost in loss record 1,612 of 1,612 ==23562==    @ 0x402a6dc: operator new(unsigned int) (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so) ==23562==    0x4c72213: std::string::_rep::_s_create(unsigned int, unsigned int, std::allocator<char> const&) (in /usr/lib/i386-linux-gnu/libstdc++.so.6.0.19) ==23562==    0x4c73332: std::string::_rep::_m_clone(std::allocator<char> const&, unsigned int) (in /usr/lib/i386-linux-gnu/libstdc++.so.6.0.19) ==23562==    0x4c733d1: std::string::reserve(unsigned int) (in /usr/lib/i386-linux-gnu/libstdc++.so.6.0.19) ==23562==    0x4c4e1ff: std::basic_stringbuf<char, std::char_traits<char>, std::allocator<char> >::overflow(int) (in /usr/lib/i386-linux-gnu/libstdc++.so.6.0.19) ==23562==    0x4c52aec: std::basic_streambuf<char, std::char_traits<char> >::xsputn(char const*, int) (in /usr/lib/i386-linux-gnu/libstdc++.so.6.0.19) ==23562==    0x4c48e8d: std::ostream::write(char const*, int) (in /usr/lib/i386-linux-gnu/libstdc++.so.6.0.19) **==23562==    0x8140eac: msgmgt::update_stream() (msgmgt.cpp:524)** ==23562==    0x814192e: msgmgt::thread() (msgmgt.cpp:727) ==23562==    0x807614e: dlib::threaded_object::thread_helper() (threaded_object_extension.cpp:256) ==23562==    0x80ebec2: void dlib::dlib_create_new_thread_helper<dlib::threaded_object, &dlib::threaded_object::thread_helper>(void*) (create_new_thread_extension.h:24) ==23562==    0x80768c3: dlib::threads_kernel_shared::thread_starter(void*) (threads_kernel_shared.cpp:272) 

the following function (udpate stream) checks pipe between process , current 1 , writes pipe content inside stringstream object, leads memory leak:

(i removed non necessary code sake of clarity)

std::stringstream _outputstream;  unsigned int msgmgt::update_stream() { fd_set set;  struct timeval timeout; //number of bytes read on pipe ssize_t read_bytes=0;  /* initialize file descriptor set. */ fd_zero(&set); fd_set(_fd[0], &set); fd_set(_fd_stop[0], &set); //allowing stop select  /* initialize timeout data structure. */ timeout.tv_sec = _timeout; timeout.tv_usec = 0;  int ret; errno=0; if(!should_stop()){      ret = select(fd_setsize, &set, null, null, &timeout);      if (ret > 0){          if(fd_isset(_fd[0],&set)){             //activity on pipe             char* buffer=new char[data_max_length];             errno=0;             //data transfer process pipe _outputstream             read_bytes = read(_fd[0],buffer,data_max_length);  //none blocking read              if(read_bytes<0 && errno !=eagain){             //error in read             }else{             //write data in stringstream             //supposed memory leak                 _outputstream.write(buffer,read_bytes);              }         delete[] buffer;           }     }  }  return read_bytes; } 

i don't understand what's going on. ideas ?

thank you,

pierre.

your buffer leaked, if _outputstream.write throws exception.

you use smart pointer store pointer buffer or use vector buffer. both solutions automatically delete in case of exception.