MISRA Discussion Forums

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?

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.

misra-c

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