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+---- Forum: 8.2 Unused code (https://forum.misra.org.uk/forumdisplay.php?fid=157)
+---- Thread: Possible inaccurate example? (/showthread.php?tid=1293)
Possible inaccurate example? - andream - 17-11-2016
The following is the example reported for Rule 2.2 (dead code):
Quote:In this example, it is assumed that the object pointed to by p is used in other functions.
Code:
extern volatile uint16_t v;
extern char *p;
void f (void ) {
uint16_t x;
(void) v; /* Compliant - v is accessed for its side effect * and the cast to void is permitted by exception */
(int32_t) v; /* Non-compliant - the cast operator is dead */
v >> 3; /* Non-compliant - the >> operator is dead */
x = 3; /* Non-compliant - the = operator is dead * - x is not subsequently read */
*p++; /* Non-compliant - result of * operator is not used */
(*p)++; /* Compliant - *p is incremented */
}I'm not sure that last but one statement represents a non-compliance. In fact, the expression *p++ is treated as *(p++), as the precedence of postfix ++ is higher than *. Indeed the result of * operator is not used, but p value results permanently increased, and p is a global variable. How can be stated that it is not compliant, alias dead code, i.e. "...whose removal would not affect program behaviour"?
Re: Possible inaccurate example? - andream - 18-11-2016
Sorry for viewers. I apologize, I simpy didn't notice that the declared non compliance, in the cited example, is not dead code, rather unused "*" operator.
Re: Possible inaccurate example? - misra-c - 09-12-2016
Rule 2.2 applies to each operator in an expression, not the expression as a whole.
As was mentioned in the 2nd post, the "*" operation is unused and constitues dead code. The expression "*p++;" could be replaced by "p++;" with no change in behaviour of the program.