16-05-2006, 12:31 PM
Hello
I use unions in the following example. And I want to know, if in such a situation the use of unions is compliant or not compliant to MISRA-C:2004. Or if somebody has a better idea for a good implementation.
A. What do you think of this little example. Good user, or bad work?
B. Compliant to rule 18.4, a situation in which unions could be used? Or not. And then, how we could do it in a MISRA-C:2004 way?
thanks a lot
Best regards,
Manni
BTW: Big thanks for your help in my last threads. My MISRA Guide proceed.
I use unions in the following example. And I want to know, if in such a situation the use of unions is compliant or not compliant to MISRA-C:2004. Or if somebody has a better idea for a good implementation.
Code:
Example_Ports.h /* eg. a processor library of a processor manufacturer */
-----------FILE START----------------
...
...
...
#define PORTA (*((volatile uint8_t *)(2000)))
/* So with \"PORTA\" we get access to data content of PORTA (adress 2000), it is a unsigned char, 8 bits. The file and this line is given by the processor manufacturer */
...
...
-----------FILE END----------------
/*Example_Test.c /* the example c file*/
-----------FILE START----------------
...
...
...
typedef union {
uint8_t cb ;
struct bits {
uint8_t
b0 : 1,
b1 : 1,
b2 : 1,
b3 : 1,
b4 : 1,
b5 : 1,
b6 : 1,
b7 : 1 ;
} b ;
}example_bitfield;
#define B7 b.b7
#define B6 b.b6
#define B5 b.b5
#define B4 b.b4
#define B3 b.b3
#define B2 b.b2
#define B1 b.b1
#define B0 b.b0
#define bitf_porta (*((volatile example_bitfield*) &PORTA))
/* Typcast to easy and safty access to each bit, see next line */
#define porta_light bitf_porta.B5
/* for a good identifier for the bit. which is for example for a light */
int main(void)
{
uint8_t x;
x = 0;
/* Now we can easy use the bits of the ports of the processor manufacturer. eg: */
porta_light = 1;
x = porta_light;
}A. What do you think of this little example. Good user, or bad work?
B. Compliant to rule 18.4, a situation in which unions could be used? Or not. And then, how we could do it in a MISRA-C:2004 way?
thanks a lot
Best regards,
Manni
BTW: Big thanks for your help in my last threads. My MISRA Guide proceed.