MISRA C++-2008 Rule 5-0-15 - Array indexing shall be the only form of pointer arithmetic

Question

I need someone who has more experience with MISRA to help me to solve this. I have the following code:

byte* buf = new(std::nothrow) byte[bufferSize];

.....
for (uint32_t i = 0; i < bufferSize; i+=4)
{

..............
                        {
buf[ i+0 ] = b;
buf[ i+1 ] = g;
buf[ i+2 ] = r;

(1) Event misra_violation:  [Required] MISRA C++-2008 Rule 5-0-15 violation: Array indexing shall be the only form of pointer arithmetic.
buf[ i+3 ] = a;

}

MISRA Rule 5-0-15 doesn't allow also ptr++ or ptr--. What should be the approach here to increment/decrement and assign values using pointers created by new?

My MISRA checker is Coverity 7.0.3.3.

Answer 1

There is no problem with your code. It uses array indexing as required. Your static analyser is broken.

Answer 2

I feel the "for" should have condition with "i+3".

for (uint32_t i = 0; i+3 < bufferSize; i+=4)

This could solve the problem. Let me know if it solves.

Answer 3

Ok, I found a way this to work:

byte* buf = new(std::nothrow) byte[bufferSize];
.....
for (uint32_t i = 0; i < bufferSize; i+=4)
{
  ..............           
  uint32_t k = i;
  buf[k] = b;
  k++;
  buf[k] = g;
  k++;
  buf[k] = r;
  k++;
  buf[k] = a;
}

It seems that MISRA does not likes the index arithmetic to be inside the [] brackets. I am not sure if this is not a bug in the tool, maybe it is fixed in the newer Coverity tools.

The following DO NOT work ( MISRA again complains with Rule 5-0-15 violation):

byte* buf = new(std::nothrow) byte[bufferSize];
.....
for (uint32_t i = 0; i < bufferSize; i+=4)
{
  ..............           
  uint32_t k = i;
  buf[k++] = b;
  buf[k++] = g;
  buf[k++] = r;
  buf[k++] = a;
}