OpenCV With HoughLines(Visual Studio C++): _CrtIsValidHeapPointer(pUserData) Breakpoint Error - c++

Question

I am still pretty new to OpenCV and I've just recently come across the HoughLinesP function. First and foremost, my goal is to write code that will detect rectangles in a webcam. Currently, the code I have below only detect lines in general. However, I still have problems while I am debugging the program. Here is my code:
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include <iostream>
using namespace cv;
using namespace std;
int main() {
int erosion_size = 0;
VideoCapture cam(0);
if (!cam.isOpened()) {
cout << "cannot open camera";
}
while (true) {
Mat frame;
cam.read(frame);
Mat gray, edge, draw, die;
cvtColor(frame, gray, CV_BGR2GRAY);
Canny(gray, edge, 100, 150, 3);
edge.convertTo(draw, CV_8U);
dilate(draw, die, Mat(), Point(-1, -1), 2, 1, 1);
erode(die, die, Mat(), Point(-1, -1), 1, 1, 1);
#if 0
vector<Vec2f> lines;
HoughLines(die, lines, 1, CV_PI / 180, 100, 0, 0);
for (size_t i = 0; i < lines.size(); i++)
{
float rho = lines[i][0], theta = lines[i][1];
Point pt1, pt2;
double a = cos(theta), b = sin(theta);
double x0 = a*rho, y0 = b*rho;
pt1.x = cvRound(x0 + 1000 * (-b));
pt1.y = cvRound(y0 + 1000 * (a));
pt2.x = cvRound(x0 - 1000 * (-b));
pt2.y = cvRound(y0 - 1000 * (a));
line(frame, pt1, pt2, Scalar(0, 0, 255), 3, CV_AA);
}
#else
vector<Vec4i> lines;
HoughLinesP(die, lines, 1, CV_PI / 180, 200, 50, 10);
for (size_t i = 0; i < lines.size(); i++)
{
Vec4i l = lines[i];
line(frame, Point(l[0], l[1]), Point(l[2], l[3]), Scalar(0, 0, 255), 3, CV_AA);
}
#endif
imshow("Canny", die);
imshow("original", frame);
if (waitKey(30) >= 0)
break;
}
return 0;
}
When I debug the program, the webcam pops up okay, but when I show a rectangular object with lines(piece of paper) it stops the program with a break point error. I concluded that my program stopped every time it found a line. When I choose to continue instead of breaking, it gives me this error:
Debug Assertion failed!
Program: ....Studio
2013/Projects/TrialRectangle/Debug/TrialRectangle.exe
File: f:/dd/vctools/crt/crtw32/misc/dbgheap.c
Line: 1332
Expression: _CrtIsValidHeapPointer(pUserData)
I played around with the HoughLinesP function and found that a high threshold parameter(ex. 500) seems to make my program run fine BUT it does not show any HoughLines at all in my webcam. If someone could explain why that is, that would be helpful as well!
Does anyone have any ideas as to how to solve this breakpoint error?

Answer 1

I got into this Debug Assertion too.
In my case, It was because that my project was statically compiled, Yet I used OpenCV dynamically with it's dll. So I change my project into dynamically compile, Solved the Problem.
It's Because that OpenCV object is allocated in different heap. And When this object is destructed, current run-time can's find that heap, This is why the Assertion is hit.