Pointers to Variable Length Arrays (VLA)

Snippet

Pointers to Variable Length Arrays (VLA)

Using a pointer to an array with a variable size (VLA) as a function parameter allows for natural multidimensional indexing (matrix[i][j]) while maintaining type safety. Unlike a pointer-to-pointer (int **), this approach ensures the data is contiguous in memory, which is critical for cache efficiency and direct mapping to row-major layouts.

snippet.c

void process_matrix(int rows, int cols, int (*matrix)[cols]) {
    for (int i = 0; i < rows; i++) {
        matrix[i][0] = i * cols;
    }
}

Breakdown

int (*matrix)[cols]

Defines a pointer to an array of 'cols' integers, where 'cols' is determined at runtime.

matrix[i][0]

Uses pointer arithmetic to skip exactly 'cols' integers per row index increment.

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Pointers to Variable Length Arrays (VLA)

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