"Internal problem" when running a MEX file the second time

Hi, I am having a problem when trying to run a .mexmaci64 file written by C++ with OpenCV the second time. I really appreciate if someone could help me.

Here is the test I did: I created a .dylib by C++ and some OpenCV stuff, and compiled it in the terminal with something like this:

g++ -dynamiclib Test.cpp -fvisibility=hidden -o libTest.dylib `pkg-config --cflags --libs opencv`

Then, in the mexFunction, I loaded this .dylib and did nothing else. It could run properly the first time, but Matlab popped up a window saying "Matlab encountered a internal problem... bla bla" when I ran it the second time.

I think it's because the dylib with OpenCV couldn't be loaded properly the second time, since I tried the same thing without the OpenCV stuff and everything is fine.

Does anyone know how to solve this? Thank you!

Answer 1

[Ken Atwell]

Does the OpenCV library have a "close" function or something similar to call before the library is unloaded? Assuming there is, you could call this as the last operation in Test.cpp.

[Liu]

Hi Ken,

Thanks for your answer. I used the dlopen() and dlclose() in a function TestArray() to load and close the dylib, and mexFunction will call TestArray(). It's something like this:

void TestArray() {

//....

void *hLib = dlopen(libName, RTLD_LOCAL);

if (!hLib) {

printf("Unable to open library:\n%s\n", libName);

printf("%s\n", dlerror());

return;

}

//......

if (dlclose(hLib)) {

printf("Unable to close library:\n%s\n", dlerror());

}

}

I tried to print something out to check at which step it crashes, and it turned out to be the dlopen() part when called the second time. I tried to put it in a try-catch, but MATLAB still reports the same thing. Maybe I should reorganise my code and separate the OpenCV part; it seems really confusing...