V2598. MISRA. Variable length array types are not allowed.

This diagnostic rule is based on the MISRA (Motor Industry Software Reliability Association) manual for software development.

This rule only applies to C. Declaring variable-length arrays can lead to a stack overflow and potential vulnerabilities in the program.

Look at the example:

void foo(size_t n)
{
  int arr[n];
  // ....
}

Transmission of large number 'n' can lead to a stack overflow as the array will become too large and take up more memory than it really is.

The most logical way is to limit the size of the array:

#define MAX_SIZE 128
void foo(size_t n)
{
  size_t size = n > MAX_SIZE ? MAX_SIZE : n;
  int arr[size];
  if (size < n) // error
  // ....
}

However, in this case it is better to use a constant to simplify the logic of the program:

#define SIZE 128
void foo()
{
  int arr[size];
  // ....
}

This will also help to avoid VLA-connected problems like calculating 'sizeof' on such arrays and passing them to other functions.

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