Infinite loop with regex (non reproducible in command line application)

pgiovanni

Let me know if you can reproduce this on your qtcreator. I have a button connected to a QlineEdit. A new window appears and is supposed to have a chart appear. But instead it gets stuck in the regex loop. The loop works in a command line app. I think the pointer std::string MBTIstring = *new std::string(this->readInMBTI->text().toStdString()); causes an error potentially. In my command line attempt passing around pointers causes a segmentation fault.

readInMBTI is the QlineEdit name btw;

Why is it infinitely looping???? it works elsewhere :(


QWidget *wdg = new QWidget;
wdg->show();

std::ifstream file("file.txt");
   std::string MBTIstring = *new std::string(this->readInMBTI->text().toStdString());
   std::string line;
   std::string returnLine;

   if(MBTIstring.length() < 17) {

       while(getline(file, line)) {
        if(line.find(MBTIstring, 0) != std::string::npos && line.find(MBTIstring, 0) < 2) {
          returnLine = line;
          break;
        }
      }
   }

  std::regex r(" *(\\w+ \\w+)");
  std::smatch m;
  auto flag = std::regex_constants::match_continuous;
  while(std::regex_search(returnLine, m, r, flag)) {
       MBTIbroken.push_back(m[1]);
       MBTIstring = m.suffix().str();
   }

JonB

@pgiovanni said in Infinite loop with regex (non reproducible in command line application):

Why is it infinitely looping???? it works elsewhere :(

  while(std::regex_search(returnLine, m, r, flag)) {
       MBTIbroken.push_back(m[1]);
       MBTIstring = m.suffix().str();
   }

Could you explain how that loop exits, assuming it enters (i.e. there is a match)? Thanks. It's pasted from your first post. And it's what I answered "No, it does not work" to.

You seem to have changed the last line to

returnLine = m.suffix().str();

later on. Why? Is one your non-working Qt code and the other your working command line one?

it works without qt involved man.

In the code you show the only bit that is "Qt" is

QWidget *wdg = new QWidget;
wdg->show();

Other than that there isn't any Qt code.

Christian Ehrlicher

@pgiovanni said in Infinite loop with regex (non reproducible in command line application):

std::string MBTIstring = *new std::string(this->readInMBTI->text().toStdString());

wtf?

while(std::regex_search(returnLine, m, r, flag))

where do you modify returnLine in your loop?

JonB

@pgiovanni said in Infinite loop with regex (non reproducible in command line application):

The loop works in a command line app.

it works elsewhere :(

No, it does not.

pgiovanni

No, it does not.

it works without qt involved man. You want proof?

pgiovanni

m.suffix().str(); should be changing it. It works in command line app as such.

#include <iostream>
#include <string>
#include <regex>
#include <vector>
#include <fstream>

int main() {
std::string returnLine;
std::vector<std::string> MBTIbroken;
std::string MBTIstring;
std::regex r(" *(\\w+ \\w+)"); // entire match will be 2 numbers
std::smatch m;
std::string line;
std::cout << "input MBTI type" << std::endl;
getline(std::cin, MBTIstring);

  std::ifstream file("jcalg hardcode.txt");

    if(MBTIstring.length() < 17) {

        while(getline(file, line)) {
         if(line.find(MBTIstring, 0) != std::string::npos && line.find(MBTIstring, 0) < 2) {
           returnLine = line;
           break;
         }
       }
    }

  auto flag = std::regex_constants::match_continuous;
  while(std::regex_search(returnLine, m, r, flag)) {
    MBTIbroken.push_back(m[1]);
    returnLine = m.suffix().str();
  }



  int i = 0;
  std::cout << "Vector Contents:" << std::endl;
  for(auto s : MBTIbroken) {
    std::cout << (++i) << ") " << s << std::endl;
  }
}

@Christian-Ehrlicher it gets the string input into the QLineEdit which is what i need? wym "wtf"

JonB

@pgiovanni said in Infinite loop with regex (non reproducible in command line application):

Why is it infinitely looping???? it works elsewhere :(

  while(std::regex_search(returnLine, m, r, flag)) {
       MBTIbroken.push_back(m[1]);
       MBTIstring = m.suffix().str();
   }

Could you explain how that loop exits, assuming it enters (i.e. there is a match)? Thanks. It's pasted from your first post. And it's what I answered "No, it does not work" to.

You seem to have changed the last line to

returnLine = m.suffix().str();

later on. Why? Is one your non-working Qt code and the other your working command line one?

it works without qt involved man.

In the code you show the only bit that is "Qt" is

QWidget *wdg = new QWidget;
wdg->show();

Other than that there isn't any Qt code.

pgiovanni

@JonB oh shit. you right. and that worked. programs crashing now, but i'll spend some time on that first. it's not the same issue.

JonB

@pgiovanni said in Infinite loop with regex (non reproducible in command line application):

No, it does not.

it works without qt involved man. You want proof?

A more productive initial reaction than this would be "I wonder if these guys actually know what they're talking about, I'll go triple-check my code in case..." :) <- Smiley