How to use resolve MISRA C error for assembly language inline function?

Question

I am using compiler related assembly language function asm() in my PIC32 MCU C code. My code is compiled and working fine with just using asm("reset") function in my C code.When checking MISRA compliance I am getting following MISRA error:

function 'asm' undeclared, assumed to return int [MISRA 2012 Rule 17.3, mandatory]asm("reset");

asm("reset");

How can I resolve this MISRA error for this assembly language function? I also tried creating function macro to use it but still getting an error.

function 'asm' undeclared, assumed to return int [MISRA 2012 Rule 17.3, mandatory]ASM_RESET(void);

#define ASM_RESET(void) asm("reset")
ASM_RESET(void);

Answer 1

It looks like PC-Lint isn't recognizing asm as a keyword. It is treating it as a function which has no prototype. You could try adding +rw(asm) to the options.

On the other hand, this forum post suggests that the legal way is to define a reset function in standalone file that includes only assembly, and show the C file a prototype for it.

reset.c:

void reset(void) {
   asm("reset");
}

test.c:

#include "reset.h"

...
reset();

Answer 2

asm is a compiler extension keyword , not a function. Being compiler specific, it is not automatically recognised by your static analysis tool,and your compiler's inline assembly syntax is "function-like", so it applies the function prototyping rule.

You need to configure PC-Lint correctly using a configuration file or command line options that describe the implementation defined behaviour of your compiler. That may include a great many options, but in this case you should use:

-dasm()=  

which will cause the analyser to ignore inline assembly code with the function-like syntax asm(...)

Alternatively you can ignore the inline assembler syntax during static analysis by conditionally defining a macro that hides all such directives:

#if defined _lint
    #define asm( asmstr )
#endif

This however would hide other deviations from the checker, such as rules about encapsulation and isolation of in-line assembly. For that reason you should not use a macro or inline assembly mixed with C code lines, but rather define a wrapper function:

void reset(void) 
{
   asm("reset");
}

and place the reset() function defined above in a separate translation unit and simply omit that source code from the analysis - as if it were library code.