<![CDATA[MISRA Discussion Forums - 8.19 Overlapping storage]]>

<![CDATA[MISRA Discussion Forums - 8.19 Overlapping storage]]> https://forum.misra.org.uk/ Thu, 05 Nov 2026 15:13:42 +0000 MyBB <![CDATA[Rule 19.1 and assigment between members of a struct]]> https://forum.misra.org.uk/showthread.php?tid=1216 Fri, 20 Nov 2015 10:34:11 +0000 GerlindeKettl]]> https://forum.misra.org.uk/showthread.php?tid=1216

Code:
struct s_tag {  

uint8 ReadPos;

uint8 WritePos; }; 

typedef struct s_tag s;

union u_tag { 

s      Elements;

uint32 Value; }; 

typedef union u_tag u; 

u NewState;

NewState.Elements.ReadPos  = NewState.Elements.WritePos;

Code:
struct s_tag {  

uint8 ReadPos;

uint8 WritePos; }; 

typedef struct s_tag s;

union u_tag { 

s      Elements;

uint32 Value; }; 

typedef union u_tag u; 

u NewState;

NewState.Elements.ReadPos  = NewState.Elements.WritePos;

My static code checker thinks it is a violation, but from my point of view I'm just assigning one member of a struct to a different member of the struct and they don't overlap in memory. That this struct is a member of a union should not matter as there is no assignment across the members of the union.]]> <![CDATA[Rule 19.1 and assignment of one element of array]]> https://forum.misra.org.uk/showthread.php?tid=1208 Thu, 29 Oct 2015 05:41:08 +0000 lovewar]]> https://forum.misra.org.uk/showthread.php?tid=1208

Code:
int16_t a[20];

void g(void) 

{

    int16_t *p = &a[0];

    int16_t *q = &a[0];

    *p = *q;              /* Compliant - exception 1 */

}

void f(void) 

{

    int16_t *p = &a[0];

    int16_t *q = &a[1];

    *p = *q;                     // here, is it Compliant ?

}

]]>

Code:
int16_t a[20];

void g(void) 

{

    int16_t *p = &a[0];

    int16_t *q = &a[0];

    *p = *q;              /* Compliant - exception 1 */

}

void f(void) 

{

    int16_t *p = &a[0];

    int16_t *q = &a[1];

    *p = *q;                     // here, is it Compliant ?

}

]]> <![CDATA[Rule 19.1 Example]]> https://forum.misra.org.uk/showthread.php?tid=1022 Wed, 22 Jan 2014 07:33:12 +0000 minoru.kanome]]> https://forum.misra.org.uk/showthread.php?tid=1022
a = b; /* Compliant - exception 1 */

a and b are not overlapping object.
Therefore, this code is improper as the example.
Is it right?]]>
a = b; /* Compliant - exception 1 */

a and b are not overlapping object.
Therefore, this code is improper as the example.
Is it right?]]>