<![CDATA[MISRA Discussion Forums - 8.18 Pointers and arrays]]>

<![CDATA[MISRA Discussion Forums - 8.18 Pointers and arrays]]> https://forum.misra.org.uk/ Thu, 05 Nov 2026 15:13:49 +0000 MyBB <![CDATA[Rule 18.8 and clarification of "use" of VLA types]]> https://forum.misra.org.uk/showthread.php?tid=1384 Fri, 27 Oct 2017 16:23:22 +0000 rgamble]]> https://forum.misra.org.uk/showthread.php?tid=1384
The example below declares a pointer to a VLA type and then dereferences the pointer:

Code:
typedef unsigned uint32_t;

typedef int int32_t;

void foo(uint32_t sz, int32_t (*ary)[sz], int32_t val) {

    (*ary)[0] = val;

}

Is the declaration of the pointer parameter ary a violation of this rule? Is the statement that dereferences ary a violation of this rule?]]>
The example below declares a pointer to a VLA type and then dereferences the pointer:

Code:
typedef unsigned uint32_t;

typedef int int32_t;

void foo(uint32_t sz, int32_t (*ary)[sz], int32_t val) {

    (*ary)[0] = val;

}

Is the declaration of the pointer parameter ary a violation of this rule? Is the statement that dereferences ary a violation of this rule?]]> <![CDATA[Rule 18.1 and Rule 11.3 compatibility]]> https://forum.misra.org.uk/showthread.php?tid=1243 Fri, 06 May 2016 15:29:42 +0000 m.bruna]]> https://forum.misra.org.uk/showthread.php?tid=1243
i am not sure about compliance of following example.

Code:
uint32_t varialble = 0;

uint8_t * ptr = (uint8_t *)variable;

(*ptr) = 0;

ptr++;        //line in question

(*ptr) = 0;        //line in question

While exception to the rule 11.3 clearly says, that converting the pointer to object to pointer to char is ok and can be used for accessing individual bytes, Rule 18.1 says that object that is not an array shall be treated as an array of single element and does not allow dereferencing a pointer beyond the end of it.

Can an object that is not an array be treated as an array of 8-bit variables with length of its byte size for this purpose? or can i only access the first byte of the object this way?

thanks,

Michal]]>
i am not sure about compliance of following example.

Code:
uint32_t varialble = 0;

uint8_t * ptr = (uint8_t *)variable;

(*ptr) = 0;

ptr++;        //line in question

(*ptr) = 0;        //line in question

While exception to the rule 11.3 clearly says, that converting the pointer to object to pointer to char is ok and can be used for accessing individual bytes, Rule 18.1 says that object that is not an array shall be treated as an array of single element and does not allow dereferencing a pointer beyond the end of it.

Can an object that is not an array be treated as an array of 8-bit variables with length of its byte size for this purpose? or can i only access the first byte of the object this way?

thanks,

Michal]]> <![CDATA[Rule 18.4, 10.1, and the "type" of pointer to object]]> https://forum.misra.org.uk/showthread.php?tid=1204 Thu, 01 Oct 2015 18:48:02 +0000 michael.metivier]]> https://forum.misra.org.uk/showthread.php?tid=1204

Code:
void test(uint8_t * up)

{

    bool invalid = !up;

    ...

}

Code:
void test(uint8_t * up)

{

    bool invalid = !up;

    ...

}

is valid with regard to the usage of '!' against a pointer. According to the 18.X rules, '!' is not disallowed for use on pointers, but the explanation of Rule 10.1 with regards to the appropriate essential type for use with '!' would indicate that, as a non-Boolean, its use on pointers should be disallowed.

Do pointers have an "essential type" under the essential type model and what is the correct interpretation in this case?]]> <![CDATA[Rule 18.4 using -- operator for pointers]]> https://forum.misra.org.uk/showthread.php?tid=1078 Thu, 17 Jul 2014 06:28:19 +0000 simondl]]> https://forum.misra.org.uk/showthread.php?tid=1078
Rule 18.4 mentions +, -, += and -= operators and also ++ operator (both post and pre fix?). -- operator is not mentioned. How to deal with it?

Regards]]>
Rule 18.4 mentions +, -, += and -= operators and also ++ operator (both post and pre fix?). -- operator is not mentioned. How to deal with it?

Regards]]>