MISRA Discussion Forums

Just wanted to know if Line 3 in the following case is a violation for Rule 12.12 ...??

1. int i;
2. float f=2.1;
3. i=(int)f >>2; //Typecasting should actually take care of the bit implementation of floats

Also, If its a violation to Rule 12.12..Does that mean all typecasts (from float to any other type) should also be considered as violationg this rule..?

In my opinion, Rule 12.12 intends to prevent direct access to the representation of floating-point values. This might typically be achieved using either a union or pointer casts, for example:

Code:
unsigned int tmp = *(unsigned int *)&f; /* get the float as 32-bit int */

tmp = tmp ^ 0x80000000;  /* flip the sign bit */

f = *(float *)&tmp;  /* store the result back */

I don't think that casting a floating-point value to int violates Rule 12.12 because there is no direct access to the representation of the value. In addition, the conversion is well-defined in that the floating point value is truncated towards zero with the result being undefined only if the truncated value won't fit in the integer type.

This example does not violate rule 12.12 as there is no access to the underlying floating representation as discussed by Steve in a previous post.

Akhil

Steve Montgomery

misra-c