I'm trying to use QtXmlPatterns module in order to parse an XML file.
Unfortunately using Qt5.1 on MacOsX 10.7&10.8 I found a problem I have not with Qt4.8.5.
#include <QCoreApplication>
#include <QGuiApplication>
#include <QXmlQuery>
#include <QStringList>
#include <QDebug>
int main(int argc, char *argv[])
{
//QGuiApplication a(argc, argv);
QCoreApplication a(argc, argv);
QXmlQuery qry;
qry.setQuery("doc(\"file.xml\")");
QStringList lst;
qry.evaluateTo(&lst);
qDebug() << lst;
return 0;
}
this is the .pro I'm using.
QT += core gui xmlpatterns
TARGET = Test
TEMPLATE = app
CONFIG -= app_bundle
SOURCES += main.cpp
If I run a QCoreApplication everything works properly, instead if I switch on QGuiApplication (or a QApplication) this small program hangs forever on the evaluteTo function. It doesn't matter if file.xml exists or not.
On Windows and on Linux the same program run smoothly even if I use the QCoreApplication or the QGuiApplication or the QApplication.
I tried also to play a little with the QXmlQuery functions. If I call the setFocus function I got the same behaviour (with QCoreApplication everything it's ok, with QGuiApplication it hangs for ever on the setFocus function).
Suggestions?
Related
I have a program using cpprestsdk for http querying and websocketpp for subscribing a data stream. The program will crash immediately(it says Process finished with exit code 139 (interrupted by signal 11: SIGSEGV)). But if I comment either of the http querying or subcribing data stream, the program won't crash.
#include <websocketpp/config/asio_client.hpp>
#include <websocketpp/client.hpp>
#include "json.hpp"
#include <iostream>
#include <ctime>
#include <iostream>
#include <cpprest/http_client.h>
#include <cpprest/filestream.h>
#include <vector>
#include <string>
using std::string;
using namespace web;
using std::cout, std::endl;
using std::vector;
using websocketpp::lib::placeholders::_1;
using websocketpp::lib::placeholders::_2;
using websocketpp::lib::bind;
typedef websocketpp::client<websocketpp::config::asio_tls_client> client;
typedef websocketpp::config::asio_client::message_type::ptr message_ptr;
void on_stream_data(websocketpp::connection_hdl hdl, message_ptr msg) {
}
class OrderBook {
public:
void initialize() {
web::http::client::http_client_config cfg;
std::string uri = string("https://fapi.binance.com/fapi/v1/depth?symbol=btcusdt&limit=1000");
web::http::client::http_client client(U(uri), cfg);
web::http::http_request request(web::http::methods::GET);
request.headers().add("Content-Type", "application/x-www-form-urlencoded");
web::http::http_response response = client.request(request).get();
}
int start_stream() {
client c;
std::string uri = string("wss://fstream.binance.com/ws/btcusdt#depth#100ms");
try {
c.set_access_channels(websocketpp::log::alevel::all);
c.clear_access_channels(websocketpp::log::alevel::frame_payload);
c.init_asio();
c.set_message_handler(bind(on_stream_data, ::_1, ::_2));
websocketpp::lib::error_code ec;
client::connection_ptr con = c.get_connection(uri, ec);
if (ec) {
std::cout << "could not create connection because: " << ec.message() << std::endl;
return 0;
}
c.connect(con);
c.run();
} catch (websocketpp::exception const &e) {
std::cout << e.what() << std::endl;
}
}
};
int main(int argc, char *argv[]) {
OrderBook ob;
ob.initialize(); // comment either of these two lines, the program won't crash, otherwise the program will crash once start
std::this_thread::sleep_for(std::chrono::milliseconds(10000000));
ob.start_stream(); // comment either of these two lines, the program won't crash, otherwise the program will crash once start
}
When I run this program in Clion debug mode, Clion show that the crash comes from function in /opt/homebrew/Cellar/boost/1.76.0/include/boost/asio/ssl/detail/impl/engine.ipp
int engine::do_connect(void*, std::size_t)
{
return ::SSL_connect(ssl_);
}
It says Exception: EXC_BAD_ACCESS (code=1, address=0xf000000000)
What's wrong with it? is it because I run two pieces of code using boost::asio, and something shouldn't be initialized twice?
I can compile this and run it fine.
My best bet is that you might be mixing versions, particularly boost versions. A common mode of failure is caused when ODR violations lead to Undefined Behaviour.
Note that these header-only libraries depend on a number of boost libraries that are not header-only (e.g. Boost System, Thread and/or Chrono). You need to compile against the same version as the libraries you link.
If you use distribution packaged versions of any library (cpprestsdk, websocketpp or whatever json library that is you're using) then you'd be safest also using the distribution packaged version of Boost.
I'd personally simplify the situation by just using Boost (Beast for HTTP/websocket, Json for, you guessed it).
Running it all on a test Ubuntu 18.04 the OS Boost 1.65 version, the start_stream sequence triggers this informative error:
[2022-05-22 13:42:11] [fatal] Required tls_init handler not present.
could not create connection because: Connection creation attempt failed
While being UBSAN/ASAN clean. Perhaps that error helps you, once you figure out the configuration problems that made your program crash.
I am creating a QR code scanner program in C++ using the library called libdecodeqr.
I downloaded all the files from https://github.com/josephholsten/libdecodeqr and I modified one of the test programs. However, I keep getting the error "unresolved external symbol". It's because I have not linked the libraries.
But I can't find libdecodeqr.lib anywhere! It's not included in the GitHub package and it's nowhere online!
In the instructions on the GitHub page, it says to add decodeqr.h, qrtypes.h, qrerror.h and libdecodeqr.lib to my environment. Other than the .lib file, I have added all those files to my environment.
Where can I find libdecodeqr.lib?
Also, here is the sample program I modified and am testing:
#include <stdio.h>
#include "opencv2/core/core.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "C:/Users/Asish/Documents/libdecodeqr-master/libdecodeqr/decodeqr.h"
#include "C:/Users/Asish/Documents/libdecodeqr-master/libdecodeqr/qrerror.h"
#include "C:/Users/Asish/Documents/libdecodeqr-master/libdecodeqr/qrtypes.h"
#include "bitstream.h"
using namespace cv;
int main(int argc, char *argv[])
{
namedWindow("src", 1);
//
// load image
//
Mat src_old = imread("qrTest.png", 1);
IplImage* src = new IplImage(src_old);
imshow("src", src_old);
//
// show version info
//
printf("libdecodeqr version %s\n", qr_decoder_version());
//
// initialize
//
QrDecoderHandle decoder = qr_decoder_open();
//
// do decode using default parameter
//
short stat = qr_decoder_decode_image(decoder, src);
printf("STATUS=%04x\n", stat);
//
// get QR code header
//
QrCodeHeader header;
if (qr_decoder_get_header(decoder, &header)){
//
// get QR code text
// To null terminate, a buffer size is larger than body size.
//
char *buf = new char[header.byte_size + 1];
qr_decoder_get_body(decoder, (unsigned char *)buf, header.byte_size + 1);
printf("%s\n", buf);
}
//
// finalize
//
qr_decoder_close(decoder);
puts("");
puts("Hit any key to end.");
cvWaitKey(0);
destroyAllWindows();
cvReleaseImage(&src);
return(0);
}
You are downloading the source code from GitHub, which means that you also need to create a new VisualStudio C++ project to compile your own libdecodeqr.lib (or dll). This will require you also install OpenCV in your computer.
How can I display colored text on the terminal from a ObjectiveC command line application?
Is there a portable way that will work both on iTerm and Terminal?
Just create a command line project and use this one as a starter. When compiling and running it you should see colors in the terminal.
#include <stdio.h>
#define KNRM "\x1B[0m"
#define KRED "\x1B[31m"
#define KGRN "\x1B[32m"
#define KYEL "\x1B[33m"
#define KBLU "\x1B[34m"
#define KMAG "\x1B[35m"
#define KCYN "\x1B[36m"
#define KWHT "\x1B[37m"
int main(int argc, const char * argv[])
{
printf("%sred\n", KRED);
printf("%sgreen\n", KGRN);
printf("%syellow\n", KYEL);
printf("%sblue\n", KBLU);
printf("%smagenta\n", KMAG);
printf("%scyan\n", KCYN);
printf("%swhite\n", KWHT);
printf("%snormal\n", KNRM);
return 0;
}
If you type set in Terminal you’ll probably see:
TERM=xterm-color
Among others. The “xterm-color” is an old way of saying what control and escape sequences the terminal will respond to, if you look that up you’ll find lots of fun things.
Is there any way to pop up a wxWidget dialog for selecting files in a command line procedure?
I am new to wxWidgets programming and it seems straightforward to pop up a selecting file dialog with FileDialog class in a wx app.
Here is my c++ code and it works fine within a wx app procedure but not in a command line one.
#include
//#include "wx/osx/filedlg.h"
#include "wx/wx.h"
#include
using namespace std;
//IMPLEMENT_APP(MyApp)
int main(int argc, const char * argv[])
{
wxFileDialog OpenDialog(NULL, wxEmptyString, wxEmptyString, wxEmptyString,
_("*"),
wxFD_MULTIPLE);
// Creates a "open file" dialog with 4 file types
if (OpenDialog.ShowModal() == wxID_OK) // if the user click "Open" instead of "cancel"
{
wxArrayString wx_str_arr;
OpenDialog.GetFilenames(wx_str_arr);
/*
for(size_t i=0; i<wx_str_arr.GetCount(); ++i)
{
wxString str = wx_str_arr.Item(i);
cout<<"str["<<i<<"] = "<<str.c_str().AsChar()<<endl;
}
*/
cout<<"count:"<<wx_str_arr.GetCount()<<endl;
}
return 0;
}
You must initialize wxWidgets correctly for this to work, see wxInitializer class for how to do it in console application.
Note that under Unix, including OS X, there is really absolutely no difference between console and GUI applications, this distinction only exists under Windows.
I have created a GUI using tcl. I want to make some of the core functionalities of the tcl code available to be used by any program which supports dll. For that i have taken a very simple tcl code example, which adds two integer numbers and i have written a c wrapper function to use this functionality. This is working for me. Now how can i create a dll for these two c and tcl files, so that any program can use this addition functionality by simply loading the dll.
Here is my simple tcl code :
/* Filename : simple_addition.tcl */
#!/usr/bin/env tclsh8.5
proc add_two_nos { } {
set a 10
set b 20
set c [expr { $a + $b } ]
puts " c is $c ......."
}
And here is my c wrapper function which uses the above tcl addition functionality :
#include <tcl.h>
#include <tclDecls.h>
#include <tclPlatDecls.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main (int argc, char **argv) {
Tcl_Interp *interp;
int code;
char *result;
printf("inside main function \n");
Tcl_FindExecutable(argv[0]);
interp = Tcl_CreateInterp();
code = Tcl_Eval(interp, "source simple_addition.tcl; add_two_nos");
/* Retrieve the result... */
result = Tcl_GetString(Tcl_GetObjResult(interp));
/* Check for error! If an error, message is result. */
if (code == TCL_ERROR) {
fprintf(stderr, "ERROR in script: %s\n", result);
exit(1);
}
/* Print (normal) result if non-empty; we'll skip handling encodings for now */
if (strlen(result)) {
printf("%s\n", result);
}
/* Clean up */
Tcl_DeleteInterp(interp);
exit(0);
}
This c wrapper is working fine for me and gives correct results.
Now I want to create a dll file, so that if i include that dll to any program that supports dll, it should be able to use this addition functionality of the above tcl code. Can anybody please tell me the way i can do it. Please help me. I am new to this dll concept.
In order to create the .dll you'll have to use something like Visual Studio and C or C++ to create the .dll (there are lots of other tools out there that can create .dll files but VS is easy to get hold of and to use.) So in VS create a new project, this needs to be a C++ WIN32 project. Select the DLL application type and the Export Symbols additional option.
VS will create a basic .dll that you can then amend to do what you want. I short I'd look at putting the creating/destruction of the intrepter into the dllmain:
BOOL APIENTRY DllMain( HMODULE hModule,
DWORD ul_reason_for_call,
LPVOID lpReserved
)
{
switch (ul_reason_for_call)
{
case DLL_PROCESS_ATTACH:
{
Tcl_FindExecutable(NULL);
interp = Tcl_CreateInterp();
}
case DLL_THREAD_ATTACH:
break ;
case DLL_THREAD_DETACH:
break ;
case DLL_PROCESS_DETACH:
{
Tcl_DeleteInterp(interp);
break;
}
}
return TRUE;
}
and then create functions exported by the .dll that make use of the interpreter. If you aren't familiar with the concept of shared libaries then I'd suggest spending a little time reading up on them, try here and here for some background reading.