MISRA Discussion Forums - 6.2 Language Extensions

Packed struct

Thu, 29 Sep 2011 10:27:55 +0000

Hi
is packing of structures allowed within Misra C?

I only wish to use the structure to overlay a generic byte array, which is populated from an external interface serialy. However the structure has 7 bytes but without packing has 8.

What i want is to be able to index into the generic array as such

sCFG *ptr = &genericArray[0];

for(i=0u; i< 10u; i++){
ptr[i].CFG0 = 10u;
..etc..
}

But because without packing the struct is 1 byte larger, i will end up misaligned.
So basically can i pack my structure to acheive this goal?

Thank you

James

FYI
typedef struct{
u8 CFG0;
u8 CFG1;
u8 CFG2;
u8 CFG3;
u8 CFG4;
u8 CFG5;
u8 CFG6;
}sCFG ;

Assembly encapsulation in macros?

Mon, 26 Apr 2010 18:41:36 +0000

Is this code compliant with rule #2.1?

Code:
#define ASM_MACRO_1 asm { "abc" }

#define ASM_MACRO_2 asm { "xyz" }

extern void g();

void f( void )

    {

    ASM_MACRO_1;    /* Do something in assembly.    */

    g();            /* Do something in C.           */

    ASM_MACRO_2;    /* Do something in assembly.    */

    }

Silencing the checker

Sun, 08 Feb 2009 08:35:07 +0000

What do people think of comments like these in code

/* defines to satisfy the MISRA checker tool */
... inevitable strange pre-processor magic

#if defined ( MISRA_CHECK )
.. behaviour 1
#endif

I see worrying amounts of it in a project I am working with and it makes me think I am working with unfinished code where the developers would rather continue writing insecure code by keeping a checker quiet than addressing the root causes. That this has been allowed by the checking tool vendor without

Does this kind of thing satisfy the spirit of MISRA and should checking tool vendors be inventing their own suppression language to litter the C-code with?

Does it break rule 2.4 - sections of code should not be commented out

Could we have a rule that bans checking tool logic, defines and comments in production code. Could we add a rule that requires checking tool vendors be required to discard the content of all well formed comments and not add mechansims for the programmer to determine if a checking tool is parsing the code? please.

Jonathan

Rule 2.1

Thu, 16 Feb 2006 07:22:58 +0000

What are the possible scenarios in which Rule 2.1 will be violated?

Rule allows for Macros, C-functions and Assembly functions.

If any assembly code is used directly it will be reported as an compliler error for undefined identifier etc.