initializing 2d std::array in a class works in release build but not in debug

Question

I'm trying to create a 2d Array class for different use cases where I know the size at compile time and that it won't change during runtime. IE setting up a grid for a battleships game.

current implementation works in both debug and release when using balanced 2d arrays such as 2 by 2, however when using unbalanced 2d arrays like 2 by 3 it will work in release but not in debug. I get expression: array subscript out of range when debugging

im using visual studio 2022 RC with std 20 enabled

header file

template <class T,unsigned int colSize,unsigned int rowSize>
  class TwoDArray{
  public:
  TwoDArray(){

    for (int i = 0; i < colSize; ++i) {
        for (int j = 0; j < rowSize; ++j) {
            matrix[i][j] = j;
            std::cout << matrix[i][j] << " ";
         }
         std::cout <<  "   " << i << std::endl;
    }

 }
  private:
  std::array<std::array<T, colSize>, rowSize> matrix;

}

in main

int main(){  

   auto p = TwoDArray<int,2 ,3>{};
   
   return 0;
}

releaseBuild for creating 2d array in class .png

debugBuild for creating 2d array in class

You mixed up colSize and rowSize in your for loops. The outer one should be rowSize — UnholySheep
– UnholySheep, Commented Nov 7, 2021 at 21:57
The debug build is being helpful and adding additional checks that you aren't going out of bounds of the array, the release build lets you do whatever you want and you get "lucky" that it doesn't crash — Alan Birtles
– Alan Birtles, Commented Nov 7, 2021 at 22:07

ZygD · Accepted Answer · 2021-11-08 05:38:48Z

0

Mixing up the colSize and rowSize in the for loops was the problem. Good to know about what the release build allows you to do.

edited Nov 8, 2021 at 5:38

ZygD

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answered Nov 8, 2021 at 3:04

matthew

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