Question

The following is a segment from a code which supposes to test communication with a server and obtain a picture from it:

bool testPICcomm(){
    Poco::Logger &logger = Poco::Logger::get("PictureTester");
    logger.setLevel(Poco::Message::PRIO_DEBUG);
    HttpClient* h = new HttpClient(host, 80);
    std::map<std::string, std::string> headers;
    Poco::UTF8Encoding utf;
    Encoder encoder(utf);


     h->connect();
     h->sendHttpRequest(askForPic,"","",0,0);
     if((h->getHttpHeaders(headers, encoder)) == false)
         {
         logger.debug("Couldn't Retrieve Headers "+ false);
         h->close();
         return false;
         }
     logger.debug("got headers");

     //get head data
     std::string mime = headers["Content-Type"];
     logger.debug("mime type:"  + mime);
     logger.debug("length string: "  + std::string((headers["Content-Length"]).c_str()));
     int length= atoi((headers["Content-Length"]).c_str());
     logger.debug("pic length:" + length);
...

I am using eclipse on linux (eclipse doesn’t function too well so im working only on the console).

Now by following logger messages i deduce that atoi (look at the end of the code) causes the segmentation fault.

Which is really weird considering that another function testXMLcomm works fine and it looks similar.

i included stdio and stdlib ofcourse.

Please Help!!!

Answer 1

I expect the crash is in the line logger.debug("pic length:" + length);. You’ve added an integer offset length to a pointer-to-string-literal, and come up with an address in no-man’s land.

You probably wanted to write something like:

ostringstream ss("pic length: ");
ss << length;
logger.debug(ss.str());

Or logger.debug("pic length: " + boost::lexical_cast<string>(length));, or C++11 has std::to_string(length).