MISRA 10.3 FALSE positive

Luděk Hezina

Hi,

I'm using TI ARM compiler v5.1.7. And I think that following case not violates MISRA rule 10.3 by casting uint32_t * to s2*. Or am I missing something?

typedef struct _s1{
uint32_t a;
uint32_t b;
}s1;

typedef struct _s2{
uint16_t d;
uint16_t e;
}s2;

void a(s1 *val);

void a(s1 *val)
{
s2 *tmp = (s2*)NULL;

tmp = (s2*)&(val->a);/** violates rule (MISRA-C:2004 10.3/R) The value of a complex expression of integer type shall only be cast to a type of the same signedness that is no wider than the underlying type of the expression */

tmp->d = 0U;
}

Luděk Hezina

over 10 years ago

0 George Mock over 10 years ago

TI__Guru**** 249900 points

I get two MISRA diagnostics for that line. Here is what it looks like ...

"file.c", line 20: warning: (MISRA-C:2004 10.3/R) The value of a complex
          expression of integer type shall only be cast to a type of the same
          signedness that is no wider than the underlying type of the
          expression
     tmp = (s2*)&(val->a); // error
                ^

"file.c", line 20: warning: (MISRA-C:2004 11.4/A) A cast should not be
          performed between a pointer to object type and a different pointer
          to object type
     tmp = (s2*)&(val->a); // error
           ^

I changed the comment on that source line to just "// error" so it will be shorter. And I build with --verbose_diagnostics to show more detail on the error. This detail includes showing the source line with a ^ character under the spot where the error starts.

I think you should be more concerned about MISRA diagnostic 11.4. That one is correct. You are taking the address of a uint32_t scalar, and casting it to the address of a s2 structure.

Thanks and regards,

-George

0 Luděk Hezina over 10 years ago in reply to George Mock

Prodigy 140 points

Yes 11.4 is correct. But 10.3 I don't see. If I write

uint32_t *uintptr = NULL;

uintptr = (uint32_t*)&(val->a);

the 10.3 is still there.

Luděk Hezina

0 George Mock over 10 years ago in reply to Luděk Hezina

TI__Guru**** 249900 points

Thank you for bringing this to our attention. I can reproduce this error, and 2 more that are similar. I filed SDSCM00051003 in the SDOWP system to have this investigated. Feel free to follow it with the SDOWP link below in my signature.

Thanks and regards,

-George

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MISRA 10.3 FALSE positive