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+--- Forum: MISRA-C: 2004 rules (https://forum.misra.org.uk/forumdisplay.php?fid=17)
+---- Forum: 6.17 Pointers and Arrays (https://forum.misra.org.uk/forumdisplay.php?fid=44)
+---- Thread: Rule 17.1 compatibility (/showthread.php?tid=856)
Rule 17.1 compatibility - misterb - 05-10-2011
Dear all,
below, you find code that shall be full MISRA-C:2004 compatible except MISRA rule 17.1 (according to my compiler). I removed the header file module.h for readability.
[code]
/* now module.c begins */
float32_t Defaults[6];
void misra17_1test(const float32_t in[6])
{
uint32_t s = 0u;
float32_t mythreshold = 0.0f;
float32_t tmpMax = 0.0f;
for (s = 0u; s < 6u; s++) {
mythreshold = in[s]; /* a MISRA 17.1 violation is detected here by compiler */
/* do something */
if (tmpMax > mythreshold) {
/* do something */
}
else {
/* do something */
}
}
}
*-----------------------------------------------------------------------------------------*/
/* now the main.c module begins */
extern float32_t Defaults[6];
int32_t main(void)
{
int32_t j = 0;
for(j=0; j
Re: Rule 17.1 compatibility - fpeelo - 05-10-2011
Rule 17.1 is "Pointer arithmetic shall only be applied to pointers that address an array or array element".
So it looks like your compiler is treating the parameter in as a pointer, not recognising that it points to an array.
According to K&R 2nd edition, "As formal parameters in a function definition,
char s[];
and
char *s;
are equivalent; we prefer the latter because it says more explicitly that the parameter is a pointer."
So maybe the compiler is reducing "const float32_t in[6]" to "const float32_t *in" before checking for MISRA violations?
Yes, your function prototype says "in[6]" but I don't believe C pays any attention to the "6".
This worries me, because I would like to have code that is as compliant as possible, and I don't see how to declare a function that operates on an array, that would be compliant. I asked here about whether it is possible (even the innocuous strlen() cannot be defined in a compliant way, unless I misunderstand).
Frank
Re: Rule 17.1 compatibility - misra-c - 06-10-2011
The parameter "in" is pointing to the first element of the array "Defaults" so the array indexing operation does not break Rule 17.1.