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R.13.5 When does a function have persistent side effects - Printable Version

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R.13.5 When does a function have persistent side effects - misra-c - 27-03-2015

Consider the following example:
Code:
bool fn ( int x )
{
   static int y;
   if ( x > 0 )
   {   y = x;  }  /* causes persistent side effect if reached */
   return ....
}

void call ( bool flag )
{
    if ( flag &&  fn(-3) ) /* Does RHS contain persistent side effect ? */
    { .... }
}
In this example the call of "fn(-3)" never executes the code "y=x" and therefore no persistent side effect will occur.
Is this a violation of rule 13.5?

Re: R.13.5 When does a function have persistent side effects - misra-c - 27-03-2015

A function is considered to have persistent side effects if there is a path through the function that might cause a persistent side effect. This determination takes no consideration of the possible values for parameters or other non-local objects.

Therefore, "fn(-3)" is considered to have persistent side effects" even though in this case the value of "y" is known not to change.