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  • Inject runtime exception to pthread sometime fails. How to fix that?

    - by lionbest
    I try to inject the exception to thread using signals, but some times the exception is not get caught. For example the following code: void _sigthrow(int sig) { throw runtime_error(strsignal(sig)); } struct sigaction sigthrow = {{&_sigthrow}}; void* thread1(void*) { sigaction(SIGINT,&sigthrow,NULL); try { while(1) usleep(1); } catch(exception &e) { cerr << "Thread1 catched " << e.what() << endl; } }; void* thread2(void*) { sigaction(SIGINT,&sigthrow,NULL); try { while(1); } catch(exception &e) { cerr << "Thread2 catched " << e.what() << endl; //never goes here } }; If I try to execute like: int main() { pthread_t p1,p2; pthread_create( &p1, NULL, &thread1, NULL ); pthread_create( &p2, NULL, &thread2, NULL ); sleep(1); pthread_kill( p1, SIGINT); pthread_kill( p2, SIGINT); sleep(1); return EXIT_SUCCESS; } I get the following output: Thread1 catched Interrupt terminate called after throwing an instance of 'std::runtime_error' what(): Interrupt Aborted How can I make second threat catch exception? Is there better idea about injecting exceptions?

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  • How to treat Base* pointer as Derived<T>* pointer?

    - by dehmann
    I would like to store pointers to a Base class in a vector, but then use them as function arguments where they act as a specific class, see here: #include <iostream> #include <vector> class Base {}; template<class T> class Derived : public Base {}; void Foo(Derived<int>* d) { std::cerr << "Processing int" << std::endl; } void Foo(Derived<double>* d) { std::cerr << "Processing double" << std::endl; } int main() { std::vector<Base*> vec; vec.push_back(new Derived<int>()); vec.push_back(new Derived<double>()); Foo(vec[0]); Foo(vec[1]); delete vec[0]; delete vec[1]; return 0; } This doesn't compile: error: call of overloaded 'Foo(Base*&)' is ambiguous Is it possible to make it work? I need to process the elements of the vector differently, according to their int, double, etc. types.

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  • CURL C API: callback was not called

    - by Pierre
    Hi all, The code below is a test for the CURL C API . The problem is that the callback function write_callback is never called. Why ? /** compilation: g++ source.cpp -lcurl */ #include <assert.h> #include <iostream> #include <cstdlib> #include <cstring> #include <cassert> #include <curl/curl.h> using namespace std; static size_t write_callback(void *ptr, size_t size, size_t nmemb, void *userp) { std::cerr << "CALLBACK WAS CALLED" << endl; exit(-1); return size*nmemb; } static void test_curl() { int any_data=1; CURLM* multi_handle=NULL; CURL* handle_curl = ::curl_easy_init(); assert(handle_curl!=NULL); ::curl_easy_setopt(handle_curl, CURLOPT_URL, "http://en.wikipedia.org/wiki/Main_Page"); ::curl_easy_setopt(handle_curl, CURLOPT_WRITEDATA, &any_data); ::curl_easy_setopt(handle_curl, CURLOPT_VERBOSE, 1); ::curl_easy_setopt(handle_curl, CURLOPT_WRITEFUNCTION, write_callback); ::curl_easy_setopt(handle_curl, CURLOPT_USERAGENT, "libcurl-agent/1.0"); multi_handle = ::curl_multi_init(); assert(multi_handle!=NULL); ::curl_multi_add_handle(multi_handle, handle_curl); int still_running=0; /* lets start the fetch */ while(::curl_multi_perform(multi_handle, &still_running) == CURLM_CALL_MULTI_PERFORM ); std::cerr << "End of curl_multi_perform."<< endl; //cleanup should go here ::exit(EXIT_SUCCESS); } int main(int argc,char** argv) { test_curl(); return 0; } Many thanks Pierre

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  • How to reliably get size of C-style array?

    - by Frank
    How do I reliably get the size of a C-style array? The method often recommended seems to be to use sizeof, but it doesn't work in the foo function, where x is passed in: #include <iostream> void foo(int x[]) { std::cerr << (sizeof(x) / sizeof(int)); // 2 } int main(){ int x[] = {1,2,3,4,5}; std::cerr << (sizeof(x) / sizeof(int)); // 5 foo(x); return 0; } Answers to this question recommend sizeof but they don't say that it (apparently?) doesn't work if you pass the array around. So, do I have to use a sentinel instead? (I don't think the users of my foo function can always be trusted to put a sentinel at the end. Of course, I could use std::vector, but then I don't get the nice shorthand syntax {1,2,3,4,5}.)

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  • What is wrong with this code for reading binary files? [on hold]

    - by qed
    What is wrong with this code for reading binary files? It compiles OK, but will not print out the file as planned, in fact, it prints nothing at all. #include <iostream> #include <fstream> int main(int argc, const char *argv[]) { if (argc < 2) { ::std::cerr << "usage: " << argv[0] << " <filename>\n"; return 1; } ::std::basic_ifstream<unsigned char> in(argv[1], ::std::ios::binary); unsigned char uc; while (in.get(uc)) { printf("%02X ", uc); } // TODO: error handling, in case the file could not be opened or read return 0; }

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  • XQuery method question, trying to sum values read from xml

    - by Buck
    I'm pretty new to XQuery and I'm trying to write an example function that I can't get to work. I want to read an xml file, parse out the "time" values, sum them as they're read and return the sum. This is trivial and I'm looking to build more functionality into it but I'd like to get this working first. Also, I know there's a "sum" directive in XQuery that would do just this but I want to add more to it so the built-in sum is insufficient for my needs. Here's my funtion: bool example(Zorba* aZorba) { XQuery_t lQuery = aZorba-compileQuery( "for $i in fn:doc('/tmp/products.xml')//time" "let $sum := xs:integer($i)" " return $sum" ); DynamicContext* lCtx = lQuery-getDynamicContext(); lCtx-setContextItemAsDocument("temp_measurements.xml", lDocStream); try { std::cout << lQuery << std::endl; } catch (DynamicException& e) { std::cerr << e.getDescription() << std::endl; return false; } catch (StaticException& f){ std::cerr << f.getDescription() << f.getErrorCodeAsString(f.getErrorCode()) << std::endl; return false; } } It's called with an appropriate main(). If I comment out the line that starts "let $sum..." then this works in that it returns the time values as a series of integers like this: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3.... Input file looks like this: <?xml version="1.0" encoding="UTF-8"? <temps <temp <time0</time <lat0</lat <long0</long <value0</value </temp <temp <time1</time <lat0</lat <long1</long <value0</value </temp ...

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  • How do I retrieve program output in Python?

    - by Geoff
    I'm not a Perl user, but from this question deduced that it's exceedingly easy to retrieve the standard output of a program executed through a Perl script using something akin to: $version = `java -version`; How would I go about getting the same end result in Python? Does the above line retrieve standard error (equivalent to C++ std::cerr) and standard log (std::clog) output as well? If not, how can I retrieve those output streams as well? Thanks, Geoff

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  • Linux termios VTIME not working?

    - by San Jacinto
    We've been bashing our heads off of this one all morning. We've got some serial lines setup between an embedded linux device and an Ubuntu box. Our reads are getting screwed up because our code usually returns two (sometimes more, sometimes exactly one) message reads instead of one message read per actual message sent. Here is the code that opens the serial port. InterCharTime is set to 4. void COMBaseClass::OpenPort() { cerr<< "openning port"<< port <<"\n"; struct termios newtio; this->fd = -1; int fdTemp; fdTemp = open( port, O_RDWR | O_NOCTTY); if (fdTemp < 0) { portOpen = 0; cerr<<"problem openning "<< port <<". Retrying"<<endl; usleep(1000000); return; } newtio.c_cflag = BaudRate | CS8 | CLOCAL | CREAD ;//| StopBits; newtio.c_iflag = IGNPAR; newtio.c_oflag = 0; /* set input mode (non-canonical, no echo,...) */ newtio.c_lflag = 0; newtio.c_cc[VTIME] = InterCharTime; /* inter-character timer in .1 secs */ newtio.c_cc[VMIN] = readBufferSize; /* blocking read until 1 char received */ tcflush(fdTemp, TCIFLUSH); tcsetattr(fdTemp,TCSANOW,&newtio); this->fd = fdTemp; portOpen = 1; } The other end is configured similarly for communication, and has one small section of particular iterest: while (1) { sprintf(out, "\r\nHello world %lu", ++ulCount); puts(out); WritePort((BYTE *)out, strlen(out)+1); sleep(2); } //while Now, when I run a read thread on the receiving machine, "hello world" is usually broken up over a couple messages. Here is some sample output: 1: Hello 2: world 1 3: Hello 4: world 2 5: Hello 6: world 3 where number followed by a colon is one message recieved. Can you see any error we are making? Thank you. Edit: For clarity, please view section 3.2 of this resource href="http://www.faqs.org/docs/Linux-HOWTO/Serial-Programming-HOWTO.html. To my understanding, with a VTIME of a couple seconds (meaning vtime is set anywhere between 10 and 50, trial-and-error), and a VMIN of 1, there should be no reason that the message is broken up over two separate messages.

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  • boost::asio::async_read_until problem

    - by user368831
    I'm trying to modify the echo server example from boost asio and I'm running into problem when I try to use boost::asio::async_read_until. Here's the code: #include <cstdlib> #include <iostream> #include <boost/bind.hpp> #include <boost/asio.hpp> using boost::asio::ip::tcp; class session { public: session(boost::asio::io_service& io_service) : socket_(io_service) { } tcp::socket& socket() { return socket_; } void start() { std::cout<<"starting"<<std::endl; boost::asio::async_read_until(socket_, boost::asio::buffer(data_, max_length), ' ', boost::bind(&session::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } void handle_read(const boost::system::error_code& error, size_t bytes_transferred) { std::cout<<"handling read"<<std::endl; if (!error) { boost::asio::async_write(socket_, boost::asio::buffer(data_, bytes_transferred), boost::bind(&session::handle_write, this, boost::asio::placeholders::error)); } else { delete this; } } void handle_write(const boost::system::error_code& error) { if (!error) { /* socket_.async_read_some(boost::asio::buffer(data_, max_length), boost::bind(&session::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); */ } else { delete this; } } private: tcp::socket socket_; enum { max_length = 1024 }; char data_[max_length]; }; class server { public: server(boost::asio::io_service& io_service, short port) : io_service_(io_service), acceptor_(io_service, tcp::endpoint(tcp::v4(), port)) { session* new_session = new session(io_service_); acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session, boost::asio::placeholders::error)); } void handle_accept(session* new_session, const boost::system::error_code& error) { if (!error) { new_session->start(); new_session = new session(io_service_); acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session, boost::asio::placeholders::error)); } else { delete new_session; } } private: boost::asio::io_service& io_service_; tcp::acceptor acceptor_; }; int main(int argc, char* argv[]) { try { if (argc != 2) { std::cerr << "Usage: async_tcp_echo_server <port>\n"; return 1; } boost::asio::io_service io_service; using namespace std; // For atoi. server s(io_service, atoi(argv[1])); io_service.run(); } catch (std::exception& e) { std::cerr << "Exception: " << e.what() << "\n"; } return 0; } The problem is when I try to compile I get this weird error: server.cpp: In member function ‘void session::start()’: server.cpp:27: error: no matching function for call to ‘async_read_until(boost::asio::basic_stream_socket &, boost::asio::mutable_buffers_1, char, boost::_bi::bind_t, boost::_bi::list3, boost::arg<1 ()(), boost::arg<2 ()() )’ Can someone please explain what's going on? From what I can tell the arguments to async_read_until are correct. Thanks!

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  • boost::asio::async_read_until problem

    - by user368831
    Hi again, I'm modify the boost asio echo example to use async_read_until to read the input word by word. Even though I am using async_read_until all the data sent seems to be read from the socket. Could someone please advise: #include <cstdlib> #include <iostream> #include <boost/bind.hpp> #include <boost/asio.hpp> using boost::asio::ip::tcp; class session { public: session(boost::asio::io_service& io_service) : socket_(io_service) { } tcp::socket& socket() { return socket_; } void start() { std::cout<<"starting"<<std::endl; boost::asio::async_read_until(socket_, buffer, ' ', boost::bind(&session::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } void handle_read(const boost::system::error_code& error, size_t bytes_transferred) { std::ostringstream ss; ss<<&buffer; std::string s = ss.str(); std::cout<<s<<std::endl; if (!error) { boost::asio::async_write(socket_, boost::asio::buffer(s), boost::bind(&session::handle_write, this, boost::asio::placeholders::error)); } else { delete this; } } void handle_write(const boost::system::error_code& error) { std::cout<<"handling write"<<std::endl; if (!error) { } else { delete this; } } private: tcp::socket socket_; boost::asio::streambuf buffer; }; class server { public: server(boost::asio::io_service& io_service, short port) : io_service_(io_service), acceptor_(io_service, tcp::endpoint(tcp::v4(), port)) { session* new_session = new session(io_service_); acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session, boost::asio::placeholders::error)); } void handle_accept(session* new_session, const boost::system::error_code& error) { if (!error) { new_session->start(); new_session = new session(io_service_); acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session, boost::asio::placeholders::error)); } else { delete new_session; } } private: boost::asio::io_service& io_service_; tcp::acceptor acceptor_; }; int main(int argc, char* argv[]) { try { if (argc != 2) { std::cerr << "Usage: async_tcp_echo_server <port>\n"; return 1; } boost::asio::io_service io_service; using namespace std; // For atoi. server s(io_service, atoi(argv[1])); io_service.run(); } catch (std::exception& e) { std::cerr << "Exception: " << e.what() << "\n"; } return 0; } Thanks!

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  • boost::asio::async_write problem

    - by user368831
    Hi, I'm trying to figure out how asynchronous reads and writes work in boost asio by manipulating the echo example. Currently, I have a server that should, when sent a sentence, respond with only the first word. However, the boost::asio::async_write never seems to complete even though the write handler is being called. Can someone please explain what's going on? Here's the code: #include <cstdlib> #include <iostream> #include <boost/bind.hpp> #include <boost/asio.hpp> using boost::asio::ip::tcp; class session { public: session(boost::asio::io_service& io_service) : socket_(io_service) { } tcp::socket& socket() { return socket_; } void start() { std::cout<<"starting"<<std::endl; boost::asio::async_read_until(socket_, buffer, ' ', boost::bind(&session::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } void handle_read(const boost::system::error_code& error, size_t bytes_transferred) { // std::ostringstream ss; // ss<<&buffer; char* c = new char[bytes_transferred]; //std::string s; buffer.sgetn(c,bytes_transferred); std::cout<<"data: "<< c<<" bytes: "<<bytes_transferred<<std::endl; if (!error) { boost::asio::async_write(socket_, boost::asio::buffer(c,bytes_transferred), boost::bind(&session::handle_write, this, boost::asio::placeholders::error)); } else { delete this; } } void handle_write(const boost::system::error_code& error) { std::cout<<"handling write"<<std::endl; if (!error) { } else { delete this; } } private: tcp::socket socket_; boost::asio::streambuf buffer; }; class server { public: server(boost::asio::io_service& io_service, short port) : io_service_(io_service), acceptor_(io_service, tcp::endpoint(tcp::v4(), port)) { session* new_session = new session(io_service_); acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session, boost::asio::placeholders::error)); } void handle_accept(session* new_session, const boost::system::error_code& error) { if (!error) { new_session->start(); new_session = new session(io_service_); acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session, boost::asio::placeholders::error)); } else { delete new_session; } } private: boost::asio::io_service& io_service_; tcp::acceptor acceptor_; }; int main(int argc, char* argv[]) { try { if (argc != 2) { std::cerr << "Usage: async_tcp_echo_server <port>\n"; return 1; } boost::asio::io_service io_service; using namespace std; // For atoi. server s(io_service, atoi(argv[1])); io_service.run(); } catch (std::exception& e) { std::cerr << "Exception: " << e.what() << "\n"; } return 0; } Thanks!

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  • Linker error when compiling boost.asio example

    - by Alon
    Hi, I'm trying to learn a little bit C++ and Boost.Asio. I'm trying to compile the following code example: #include <iostream> #include <boost/array.hpp> #include <boost/asio.hpp> using boost::asio::ip::tcp; int main(int argc, char* argv[]) { try { if (argc != 2) { std::cerr << "Usage: client <host>" << std::endl; return 1; } boost::asio::io_service io_service; tcp::resolver resolver(io_service); tcp::resolver::query query(argv[1], "daytime"); tcp::resolver::iterator endpoint_iterator = resolver.resolve(query); tcp::resolver::iterator end; tcp::socket socket(io_service); boost::system::error_code error = boost::asio::error::host_not_found; while (error && endpoint_iterator != end) { socket.close(); socket.connect(*endpoint_iterator++, error); } if (error) throw boost::system::system_error(error); for (;;) { boost::array<char, 128> buf; boost::system::error_code error; size_t len = socket.read_some(boost::asio::buffer(buf), error); if (error == boost::asio::error::eof) break; // Connection closed cleanly by peer. else if (error) throw boost::system::system_error(error); // Some other error. std::cout.write(buf.data(), len); } } catch (std::exception& e) { std::cerr << e.what() << std::endl; } return 0; } With the following command line: g++ -I /usr/local/boost_1_42_0 a.cpp and it throws an unclear error: /tmp/ccCv9ZJA.o: In function `__static_initialization_and_destruction_0(int, int)': a.cpp:(.text+0x654): undefined reference to `boost::system::get_system_category()' a.cpp:(.text+0x65e): undefined reference to `boost::system::get_generic_category()' a.cpp:(.text+0x668): undefined reference to `boost::system::get_generic_category()' a.cpp:(.text+0x672): undefined reference to `boost::system::get_generic_category()' a.cpp:(.text+0x67c): undefined reference to `boost::system::get_system_category()' /tmp/ccCv9ZJA.o: In function `boost::system::error_code::error_code()': a.cpp:(.text._ZN5boost6system10error_codeC2Ev[_ZN5boost6system10error_codeC5Ev]+0x10): undefined reference to `boost::system::get_system_category()' /tmp/ccCv9ZJA.o: In function `boost::asio::error::get_system_category()': a.cpp:(.text._ZN5boost4asio5error19get_system_categoryEv[boost::asio::error::get_system_category()]+0x7): undefined reference to `boost::system::get_system_category()' /tmp/ccCv9ZJA.o: In function `boost::asio::detail::posix_thread::~posix_thread()': a.cpp:(.text._ZN5boost4asio6detail12posix_threadD2Ev[_ZN5boost4asio6detail12posix_threadD5Ev]+0x1d): undefined reference to `pthread_detach' /tmp/ccCv9ZJA.o: In function `boost::asio::detail::posix_thread::join()': a.cpp:(.text._ZN5boost4asio6detail12posix_thread4joinEv[boost::asio::detail::posix_thread::join()]+0x25): undefined reference to `pthread_join' /tmp/ccCv9ZJA.o: In function `boost::asio::detail::posix_tss_ptr<boost::asio::detail::call_stack<boost::asio::detail::task_io_service<boost::asio::detail::epoll_reactor<false> > >::context>::~posix_tss_ptr()': a.cpp:(.text._ZN5boost4asio6detail13posix_tss_ptrINS1_10call_stackINS1_15task_io_serviceINS1_13epoll_reactorILb0EEEEEE7contextEED2Ev[_ZN5boost4asio6detail13posix_tss_ptrINS1_10call_stackINS1_15task_io_serviceINS1_13epoll_reactorILb0EEEEEE7contextEED5Ev]+0xf): undefined reference to `pthread_key_delete' /tmp/ccCv9ZJA.o: In function `boost::asio::detail::posix_tss_ptr<boost::asio::detail::call_stack<boost::asio::detail::task_io_service<boost::asio::detail::epoll_reactor<false> > >::context>::posix_tss_ptr()': a.cpp:(.text._ZN5boost4asio6detail13posix_tss_ptrINS1_10call_stackINS1_15task_io_serviceINS1_13epoll_reactorILb0EEEEEE7contextEEC2Ev[_ZN5boost4asio6detail13posix_tss_ptrINS1_10call_stackINS1_15task_io_serviceINS1_13epoll_reactorILb0EEEEEE7contextEEC5Ev]+0x22): undefined reference to `pthread_key_create' collect2: ld returned 1 exit status How can I fix it? Thank you.

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  • Does boost::asio makes excessive small heap allocations or am I wrong?

    - by Poni
    #include <cstdlib> #include <iostream> #include <boost/bind.hpp> #include <boost/asio.hpp> using boost::asio::ip::tcp; class session { public: session(boost::asio::io_service& io_service) : socket_(io_service) { } tcp::socket& socket() { return socket_; } void start() { socket_.async_read_some(boost::asio::buffer(data_, max_length - 1), boost::bind(&session::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } void handle_read(const boost::system::error_code& error, size_t bytes_transferred) { if (!error) { data_[bytes_transferred] = '\0'; if(NULL != strstr(data_, "quit")) { this->socket().shutdown(boost::asio::ip::tcp::socket::shutdown_both); this->socket().close(); // how to make this dispatch "handle_read()" with a "disconnected" flag? } else { boost::asio::async_write(socket_, boost::asio::buffer(data_, bytes_transferred), boost::bind(&session::handle_write, this, boost::asio::placeholders::error)); socket_.async_read_some(boost::asio::buffer(data_, max_length - 1), boost::bind(&session::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } } else { delete this; } } void handle_write(const boost::system::error_code& error) { if (!error) { // } else { delete this; } } private: tcp::socket socket_; enum { max_length = 1024 }; char data_[max_length]; }; class server { public: server(boost::asio::io_service& io_service, short port) : io_service_(io_service), acceptor_(io_service, tcp::endpoint(tcp::v4(), port)) { session* new_session = new session(io_service_); acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session, boost::asio::placeholders::error)); } void handle_accept(session* new_session, const boost::system::error_code& error) { if (!error) { new_session->start(); new_session = new session(io_service_); acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session, boost::asio::placeholders::error)); } else { delete new_session; } } private: boost::asio::io_service& io_service_; tcp::acceptor acceptor_; }; int main(int argc, char* argv[]) { try { if (argc != 2) { std::cerr << "Usage: async_tcp_echo_server <port>\n"; return 1; } boost::asio::io_service io_service; using namespace std; // For atoi. server s(io_service, atoi(argv[1])); io_service.run(); } catch (std::exception& e) { std::cerr << "Exception: " << e.what() << "\n"; } return 0; } While experimenting with boost::asio I've noticed that within the calls to async_write()/async_read_some() there is a usage of the C++ "new" keyword. Also, when stressing this echo server with a client (1 connection) that sends for example 100,000 times some data, the memory usage of this program is getting higher and higher. What's going on? Will it allocate memory for every call? Or am I wrong? Asking because it doesn't seem right that a server app will allocate, anything. Can I handle it, say with a memory pool? Another side-question: See the "this-socket().close();" ? I want it, as the comment right to it says, to dispatch that same function one last time, with a disconnection error. Need that to do some clean-up. How do I do that? Thank you all gurus (:

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  • bind() fails with windows socket error 10038

    - by herrturtur
    I'm trying to write a simple program that will receive a string of max 20 characters and print that string to the screen. The code compiles, but I get a bind() failed: 10038. After looking up the error number on msdn (socket operation on nonsocket), I changed some code from int sock; to SOCKET sock which shouldn't make a difference, but one never knows. Here's the code: #include <iostream> #include <winsock2.h> #include <cstdlib> using namespace std; const int MAXPENDING = 5; const int MAX_LENGTH = 20; void DieWithError(char *errorMessage); int main(int argc, char **argv) { if(argc!=2){ cerr << "Usage: " << argv[0] << " <Port>" << endl; exit(1); } // start winsock2 library WSAData wsaData; if(WSAStartup(MAKEWORD(2,0), &wsaData)!=0){ cerr << "WSAStartup() failed" << endl; exit(1); } // create socket for incoming connections SOCKET servSock; if(servSock=socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)==INVALID_SOCKET) DieWithError("socket() failed"); // construct local address structure struct sockaddr_in servAddr; memset(&servAddr, 0, sizeof(servAddr)); servAddr.sin_family = AF_INET; servAddr.sin_addr.s_addr = INADDR_ANY; servAddr.sin_port = htons(atoi(argv[1])); // bind to the local address int servAddrLen = sizeof(servAddr); if(bind(servSock, (SOCKADDR*)&servAddr, servAddrLen)==SOCKET_ERROR) DieWithError("bind() failed"); // mark the socket to listen for incoming connections if(listen(servSock, MAXPENDING)<0) DieWithError("listen() failed"); // accept incoming connections int clientSock; struct sockaddr_in clientAddr; char buffer[MAX_LENGTH]; int recvMsgSize; int clientAddrLen = sizeof(clientAddr); for(;;){ // wait for a client to connect if((clientSock=accept(servSock, (sockaddr*)&clientAddr, &clientAddrLen))<0) DieWithError("accept() failed"); // clientSock is connected to a client // BEGIN Handle client cout << "Handling client " << inet_ntoa(clientAddr.sin_addr) << endl; if((recvMsgSize = recv(clientSock, buffer, MAX_LENGTH, 0)) <0) DieWithError("recv() failed"); cout << "Word in the tubes: " << buffer << endl; closesocket(clientSock); // END Handle client } } void DieWithError(char *errorMessage) { fprintf(stderr, "%s: %d\n", errorMessage, WSAGetLastError()); exit(1); }

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  • Are free operator->* overloads evil?

    - by Potatoswatter
    I was perusing section 13.5 after refuting the notion that built-in operators do not participate in overload resolution, and noticed that there is no section on operator->*. It is just a generic binary operator. Its brethren, operator->, operator*, and operator[], are all required to be non-static member functions. This precludes definition of a free function overload to an operator commonly used to obtain a reference from an object. But the uncommon operator->* is left out. In particular, operator[] has many similarities. It is binary (they missed a golden opportunity to make it n-ary), and it accepts some kind of container on the left and some kind of locator on the right. Its special-rules section, 13.5.5, doesn't seem to have any actual effect except to outlaw free functions. (And that restriction even precludes support for commutativity!) So, for example, this is perfectly legal (in C++0x, remove obvious stuff to translate to C++03): #include <utility> #include <iostream> #include <type_traits> using namespace std; template< class F, class S > typename common_type< F,S >::type operator->*( pair<F,S> const &l, bool r ) { return r? l.second : l.first; } template< class T > T & operator->*( pair<T,T> &l, bool r ) { return r? l.second : l.first; } template< class T > T & operator->*( bool l, pair<T,T> &r ) { return l? r.second : r.first; } int main() { auto x = make_pair( 1, 2.3 ); cerr << x->*false << " " << x->*4 << endl; auto y = make_pair( 5, 6 ); y->*(0) = 7; y->*0->*y = 8; // evaluates to 7->*y = y.second cerr << y.first << " " << y.second << endl; } I can certainly imagine myself giving into temp[la]tation. For example, scaled indexes for vector: v->*matrix_width[2][5] = x; Did the standards committee forget to prevent this, was it considered too ugly to bother, or are there real-world use cases?

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  • Are there supposed to be more restrictions on operator->* overloads?

    - by Potatoswatter
    I was perusing section 13.5 after refuting the notion that built-in operators do not participate in overload resolution, and noticed that there is no section on operator->*. It is just a generic binary operator. Its brethren, operator->, operator*, and operator[], are all required to be non-static member functions. This precludes definition of a free function overload to an operator commonly used to obtain a reference from an object. But the uncommon operator->* is left out. In particular, operator[] has many similarities. It is binary (they missed a golden opportunity to make it n-ary), and it accepts some kind of container on the left and some kind of locator on the right. Its special-rules section, 13.5.5, doesn't seem to have any actual effect except to outlaw free functions. (And that restriction even precludes support for commutativity!) So, for example, this is perfectly legal (in C++0x, remove obvious stuff to translate to C++03): #include <utility> #include <iostream> #include <type_traits> using namespace std; template< class F, class S > typename common_type< F,S >::type operator->*( pair<F,S> const &l, bool r ) { return r? l.second : l.first; } template< class T > T & operator->*( pair<T,T> &l, bool r ) { return r? l.second : l.first; } template< class T > T & operator->*( bool l, pair<T,T> &r ) { return l? r.second : r.first; } int main() { auto x = make_pair( 1, 2.3 ); cerr << x->*false << " " << x->*4 << endl; auto y = make_pair( 5, 6 ); y->*(0) = 7; y->*0->*y = 8; // evaluates to 7->*y = y.second cerr << y.first << " " << y.second << endl; } I can certainly imagine myself giving into temp[la]tation. For example, scaled indexes for vector: v->*matrix_width[5] = x; Did the standards committee forget to prevent this, was it considered too ugly to bother, or are there real-world use cases?

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  • failbit is being set and I can't figure out why

    - by felipedrl
    I'm writing a MIDI file loader. Everything is going fine until at some track I get a failbit exception while trying to read from file. I can't figure out why, I've checked the file size and it's ok too. Upon checking "errno" and it returns "0". Any ideas? Thanks. The snippet follows: file.read(reinterpret_cast<char*>(&mHeader.id), sizeof(MidiHeader)); mTracks = new MidiTrack[mHeader.nTracks]; for (uint i = 0; i < mHeader.nTracks; ++i) { // this read fails on 6th i. I've checked hexadecimal file and it's // ok so far. file.read(reinterpret_cast<char*>(&mTracks[i].id), sizeof(uint)); if (file.fail()) { std::cerr << errno << std::endl; massert(false); } massert(mTracks[i].id == 0x6B72544D); file.read(reinterpret_cast<char*>(&mTracks[i].size), sizeof(uint)); mTracks[i].size = swapBytes(mTracks[i].size); mTracks[i].data = new char[mTracks[i].size]; file.read(mTracks[i].data, mTracks[i].size * sizeof(char)); totalBytesRead += 8 + mTracks[i].size; massert(totalBytesRead <= fileSize); }

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  • Basic SDL2 Code which "Stop working" when calling SDL_Quit() [migrated]

    - by Rivten
    So I got into SDL2 with C++ quite recently and I did this very simple code : int main(int argc, char** argv) { SDL_Event *event; bool done = false; if(SDL_Init(SDL_INIT_VIDEO) != 0) { std::cerr << "Problèmes pour initialiser la SDL : " << SDL_GetError() << std::endl; return 1; } SDL_Window *window = 0; window = SDL_CreateWindow("Mopion", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, WIDTH, HEIGHT, SDL_WINDOW_SHOWN); if(window == 0) { done = true; } while(!done) { while(SDL_PollEvent(event)) { switch(event->type) { case SDL_QUIT: done = true; break; case SDL_KEYUP: if(event->key.keysym.sym == SDLK_q) { done = true; } break; default: break; } } } SDL_DestroyWindow(window); SDL_Quit(); return 0; } While that code executes at first quite well, when I hit the "Q" key, the window closes but I got a Windows Error Window saying that "My program stopped working." which is not very convenient. Using the debugger, I found that everything is fine until SDL_Quit() is called. Anyone has any idea why this is going on ? Thanks a lot !

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  • SDK mouse relative motion, weird results

    - by zaftcoAgeiha
    I have a simple SDL application that tracks the relative change in mouse position But for some reason, the motion.xrel and motion.yrel give back massive numbers! my code: SDL_WM_GrabInput(SDL_GRAB_ON); SDL_ShowCursor(false); while(!quit){ // Draw the scene if (invalidated == 1){ on_render(); invalidated = 0; } // And poll for events SDL_PumpEvents(); SDL_Event event; while ( SDL_PollEvent(&event) ) { switch (event.type) { case SDL_KEYDOWN: case SDL_KEYUP: on_key(event.key); break; case SDL_MOUSEMOTION: std::cerr << event.motion.xrel << ":" << event.motion.yrel << std::endl; invalidated = 1; break; ... and the printed results are ridiculous: 400:300 -11297:1705 -11215:1268 -10969:940 -10314:-43 -9986:-698 -9331:-1681 -9003:-2227 -8593:-2664 -8020:-3538 -7774:-3647 -7365:-4193 -7283:-4302 -7119:0 any idea why?? System is Ubuntu 12 running in virtual box

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  • Of these 3 methods for reading linked lists from shared memory, why is the 3rd fastest?

    - by Joseph Garvin
    I have a 'server' program that updates many linked lists in shared memory in response to external events. I want client programs to notice an update on any of the lists as quickly as possible (lowest latency). The server marks a linked list's node's state_ as FILLED once its data is filled in and its next pointer has been set to a valid location. Until then, its state_ is NOT_FILLED_YET. I am using memory barriers to make sure that clients don't see the state_ as FILLED before the data within is actually ready (and it seems to work, I never see corrupt data). Also, state_ is volatile to be sure the compiler doesn't lift the client's checking of it out of loops. Keeping the server code exactly the same, I've come up with 3 different methods for the client to scan the linked lists for changes. The question is: Why is the 3rd method fastest? Method 1: Round robin over all the linked lists (called 'channels') continuously, looking to see if any nodes have changed to 'FILLED': void method_one() { std::vector<Data*> channel_cursors; for(ChannelList::iterator i = channel_list.begin(); i != channel_list.end(); ++i) { Data* current_item = static_cast<Data*>(i->get(segment)->tail_.get(segment)); channel_cursors.push_back(current_item); } while(true) { for(std::size_t i = 0; i < channel_list.size(); ++i) { Data* current_item = channel_cursors[i]; ACQUIRE_MEMORY_BARRIER; if(current_item->state_ == NOT_FILLED_YET) { continue; } log_latency(current_item->tv_sec_, current_item->tv_usec_); channel_cursors[i] = static_cast<Data*>(current_item->next_.get(segment)); } } } Method 1 gave very low latency when then number of channels was small. But when the number of channels grew (250K+) it became very slow because of looping over all the channels. So I tried... Method 2: Give each linked list an ID. Keep a separate 'update list' to the side. Every time one of the linked lists is updated, push its ID on to the update list. Now we just need to monitor the single update list, and check the IDs we get from it. void method_two() { std::vector<Data*> channel_cursors; for(ChannelList::iterator i = channel_list.begin(); i != channel_list.end(); ++i) { Data* current_item = static_cast<Data*>(i->get(segment)->tail_.get(segment)); channel_cursors.push_back(current_item); } UpdateID* update_cursor = static_cast<UpdateID*>(update_channel.tail_.get(segment)); while(true) { if(update_cursor->state_ == NOT_FILLED_YET) { continue; } ::uint32_t update_id = update_cursor->list_id_; Data* current_item = channel_cursors[update_id]; if(current_item->state_ == NOT_FILLED_YET) { std::cerr << "This should never print." << std::endl; // it doesn't continue; } log_latency(current_item->tv_sec_, current_item->tv_usec_); channel_cursors[update_id] = static_cast<Data*>(current_item->next_.get(segment)); update_cursor = static_cast<UpdateID*>(update_cursor->next_.get(segment)); } } Method 2 gave TERRIBLE latency. Whereas Method 1 might give under 10us latency, Method 2 would inexplicably often given 8ms latency! Using gettimeofday it appears that the change in update_cursor-state_ was very slow to propogate from the server's view to the client's (I'm on a multicore box, so I assume the delay is due to cache). So I tried a hybrid approach... Method 3: Keep the update list. But loop over all the channels continuously, and within each iteration check if the update list has updated. If it has, go with the number pushed onto it. If it hasn't, check the channel we've currently iterated to. void method_three() { std::vector<Data*> channel_cursors; for(ChannelList::iterator i = channel_list.begin(); i != channel_list.end(); ++i) { Data* current_item = static_cast<Data*>(i->get(segment)->tail_.get(segment)); channel_cursors.push_back(current_item); } UpdateID* update_cursor = static_cast<UpdateID*>(update_channel.tail_.get(segment)); while(true) { for(std::size_t i = 0; i < channel_list.size(); ++i) { std::size_t idx = i; ACQUIRE_MEMORY_BARRIER; if(update_cursor->state_ != NOT_FILLED_YET) { //std::cerr << "Found via update" << std::endl; i--; idx = update_cursor->list_id_; update_cursor = static_cast<UpdateID*>(update_cursor->next_.get(segment)); } Data* current_item = channel_cursors[idx]; ACQUIRE_MEMORY_BARRIER; if(current_item->state_ == NOT_FILLED_YET) { continue; } found_an_update = true; log_latency(current_item->tv_sec_, current_item->tv_usec_); channel_cursors[idx] = static_cast<Data*>(current_item->next_.get(segment)); } } } The latency of this method was as good as Method 1, but scaled to large numbers of channels. The problem is, I have no clue why. Just to throw a wrench in things: if I uncomment the 'found via update' part, it prints between EVERY LATENCY LOG MESSAGE. Which means things are only ever found on the update list! So I don't understand how this method can be faster than method 2. The full, compilable code (requires GCC and boost-1.41) that generates random strings as test data is at: http://pastebin.com/e3HuL0nr

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  • is memset(ary,0,length) a portable way of inputting zero in double array

    - by monkeyking
    The following code uses memset to set all the bits to zero #include <iostream> #include <cstring> int main(){ int length = 5; double *array = new double[length]; memset(array,0,sizeof(double)*length); for(int i=0;i<length;i++) if(array[i]!=0.0) std::cerr<< "not zero in: " <<i <<std::endl; return 0; } Can I assume that this will work on all platforms? Does the double datatype always correspond to the ieee-754 standard? thanks

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  • C++ std::equal -- rationale behind not testing for the 2 ranges having equal size?

    - by ShaChris23
    I just wrote some code to test the behavior of std::equal, and came away surprised: int main() { try { std::list<int> lst1; std::list<int> lst2; if(!std::equal(lst1.begin(), lst1.end(), lst2.begin())) throw std::logic_error("Error: 2 empty lists should always be equal"); lst2.push_back(5); if(std::equal(lst1.begin(), lst1.end(), lst2.begin())) throw std::logic_error("Error: comparing 2 lists where one is not empty should not be equal"); } catch(std::exception& e) { std::cerr << e.what(); } } The output (a surprise to me): Error: comparing 2 lists where one is not empty should not be equal Observation: why is it the std::equal does not first check if the 2 containers have the same size() ? Was there a legitimate reason?

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  • Why Does try ... catch Blocks Require Braces?

    - by Bidou
    Hello. While in other statements like if ... else you can avoid braces if there is only one instruction in a block, you cannot do that with try ... catch blocks: the compiler doesn't buy it. For instance: try do_something_risky(); catch (...) std::cerr << "Blast!" << std::endl; With the code above, g++ simply says it expects a '{' before do_something_risky(). Why this difference of behavior between try ... catch and, say, if ... else ? Thanks!

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  • Loading Unmanaged C++ in C#. Error Attempted to read or write protected memory

    - by Thatoneguy
    I have a C++ function that looks like this __declspec(dllexport) int ___stdcall RegisterPerson(char const * const szName) { std::string copyName( szName ); // Assign name to a google protocol buffer object // Psuedo code follows.. Protobuf::Person person; person->set_name(copyName); // Error Occurs here... std::cerr << person->DebugString() << std::endl; } The corresponding C# code looks like this... [DllImport(@"MyLibrary.dll", SetLastError = true)] public static unsafe extern int RegisterPerson([MarshalAs(UnmanagedType.LPTStr)]string szName) Not sure why this is not working. My C++ library is compiled as Multi Threaded DLL with MultiByte encoding. Any help would be appreciated. I saw this is a common problem online but no answers lead me to a solution for my problem.

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