MISRA Discussion Forums - 6.20 Standard Libraries

Executing process

Sun, 17 Nov 2019 22:40:04 +0000

Hello,

Regarding the rule 20.11, the call of 'system' shall not be used. But In my current program, I'm creating process by using fork() and system() to start it.

What is the best solution to create process and start it in order to comply with MISRA C 2004 ?

By advance thanks for your answer.

MISRA 20.2

Thu, 26 Apr 2018 14:18:46 +0000

Hello,

Why the following code is the violation of MISRA 20.2 ?

Code:
#define abs(a)   (((a) < (0)) ? -(a) : (a))

As far as I understand from the topics , 20.2 does not concern with preprocessor identifier then why I get an violation for the same.

Misra rule 20.3

Wed, 01 Mar 2017 11:31:01 +0000

Code:
#define MAX_BUF_LEN 20

#define MAX_ID_LEN    40

typedef struct

{

uint8_t  sno[MAX_BUF_LEN];

uint8_t  ID[MAX_ID_LEN ];'

} xdata_t;

typedef {

uint8_t   time;

uint32_t vol;

uint8_t ID[MAX_ID_LEN ];

}xpf_t

xdata_t  testdata;

xpf_t      pfdata

....

memcpy(pfdata.ID, testdata.ID, MAX_ID_LEN );  // Misra not compliant

......

I am using parasoft tool for checking misra compliance. for the above memcpy line I am getting the following misra non compliance

Values is "ID" passed to library function "memcpy" without being checked

I am using statically declared array. Why is it throwing this misra compliance? Can any one point how to make thsi line compliant

TIA
Narendra

MISRA rule 20.1 and 20.2

Fri, 14 Mar 2014 18:53:59 +0000

20.1 (req): %s: Reserved identifiers, macros and functions in the standard library, shall not be defined, redefined or undefined.
20.2 (req): %s: The names of standard library macros, objects and functions shall not be reused.

As per the rule 20.1, Reserved identifiers should not be defined, redefined or undefined.
I am getting the violation of MISRA 20.2 for the below example:

For the declaration,
int for;
'for' is the reserve identifier. It is re-defined as variable declaration and it is not used in any standard library.
Hence it should violates the MISRA rule 20.1 and not MISRA rule 20.2.

Please explain the difference between MISRA 20.1 and 20.2 rules with suitable examples.

Dynamic memory allocation - rule 20.4

Thu, 13 Dec 2012 11:49:16 +0000

Hi,

I missed discussion about new Misra C to be released.
Anyway now and then I have several questions and comments about dynamic memory allocation.

In Misra C 2004 there is only one rule (20.4) addressing dynamic memory allocation.
In my opinion it's too little. There are questions not answered by this single rule.

So the questions are:
1. Is this rule only forbiding use of malloc, calloc, realloc and free functions while leaving a room for implementation and use of prorpietary functions?

2. Is proprietary dynamic memory management allowed in any way?

3. I would like to implement my own "heap" (pool) which would allow for memory allocation on startup only and no deallocation anytime. Is this possible without violation of this rule?

In my opinion these questions should be answered in new Misra in some clearer way.

Best regards,
Szymon

about rule20_5

Tue, 15 Jun 2010 06:38:50 +0000

void func()
{
int errno;//does even declaration of errno violates rule20_5,errno is user defined?
}

about rule20.5

Tue, 25 May 2010 12:18:47 +0000

According to the rule 20.5, error indiaction facility should not be used even if it is well defined.
1)Is it mean that we should not declare the identifier(function and variable) with the name "errno"?
2)As per the standard library for linux "errno" MACRO is defined to function pointer call and for Visual C++ it is extern variable declaration. So does usage of "errno"(i.e. function call) on linux also violates the rule 20.5?

Do not use the sizeof() operator

Mon, 03 Aug 2009 13:13:12 +0000

I would suggest a new rule for MISRA C.
"Do not use the sizeof() operator".
Output seems to be compiler dependent, e.g. TI compiler for TMS320C2x/C2xx/C5x series returns the number of 16bit units.

They (TI) claim, that there is an ambiguity in the ANSI C definition:
- sizeof() shall return the number of bytes
- sizeof(char) shall return 1
As they implement a char as 16 bit, their solution of the dilemma is to define a byte as 16 bit.

This sounds problematic and will cause issues while porting code, which uses the sizeof() operator.

Clarification Needed on Rule 20.12

Thu, 05 Mar 2009 15:24:35 +0000

Rule says not to use any functionality of and it is a Required rule.

How to use POSIX compliant timer APIs like timer_create, timer_settime etc is also defined in this header file?

20.1, 20.2 scopes

Thu, 15 May 2008 13:08:18 +0000

Is rule 20.1 limited to #define and #undef directives?
Is rule 20.2 limited only to identifiers already defined in standard library?

If this is true:

Code:
void errno(); 

/* errono is a reserved keyword and is already defined in standard library */

/* This code is a violation of rule 20.2 only  */

int __MyVariable(); 

/* __MyVariable is also a reserved keyword but is not defined in standard library */

/* This code is not a violation of 20.1 nor 20.2 */

Rule 20.9

Tue, 21 Feb 2006 10:56:15 +0000

Rule 20.9 says that the input/output library shall not be used in production code.

We can not use the function open because is not ANSI C. Which would be the alternative to open a file instead of fopen?

Thanks.

Is Rule 20.1 applicable to \"defined\"?

Fri, 09 Sep 2005 13:30:17 +0000

Question: Is Rule 20.1 applicable to \"defined\"?

(a) We presume that \"#define defined (10)\" will be in violation of Rule 20.1.

(b) If our presumption is correct, then which of \"reserved identifier\", \" macro\" or \"function\" will \"defined\" be?
We could not find the answer in ISO/IEC 9899:1990. Is it described somewhere in COR1, COR2 or AMD1?

Answer: MISRA C Steering Team 7/9/2005

(a) YES - defined is included in the text under the rule.

(b) defined is listed under 6.8.8 Predefined Macro Names.
It is also listed in Appendix G: Undefined Behaviour 54.

What about keywords?

Fri, 09 Sep 2005 13:04:17 +0000

Question:

Is it correct to think that a keyword is out of the scope of Rule 20.1?

For example, \"#define int (10)\" violates Rule 19.4, doesn't it?

Answer: MISRA C Steering Team 7/9/2005

Keywords (as defined in 6.1.1) shall be considered to be in the scope of 20.1.
This is detailed in the supporting text and will be clarified in the Technical Corrigendum.

#define int (10)

This is not a violation of 19.4.

19.4 is concerned with the replacement text of a macro, and not its name.

Clarification of 20.1 - Intrepretation of \"not to be d

Fri, 09 Sep 2005 13:00:50 +0000

Question 2: Interpretation of \"not be defined, redefined\"

a) Does it mean that \"#define\" is not allowed?

b) Is it not allowed to define as an object or a function, either?

Answer: MISRA C Steering Team clarification 7/9/2005

(a) YES - To define an object or a function with the name of a reserved identifier is prohibited under rule 20.2.

(b) YES - To #define macros with the name of a reserved identifier is prohibited.

Clarification of 20.1 Scope

Fri, 09 Sep 2005 12:57:03 +0000

Question:

Question 1: Interpretation of \"Reserved identifiers, macros and functions in the standard library\"

Does this phrase mean
a) \"Reserved identifiers
AND
macros in the standard library
AND
functions in the standard library\"
or
b) \"Reserved identifiers in the standard library
AND
macros in the standard library
AND
functions in the standard library\" ?

It seems that in case of a) above, \"#define __ABC (10)\" violates Rule 20.1 whereas it does not in case of b), because \"__ABC\", which is a reserved identifier, is not in the standard library. Moreover, it is not guaranteed that all of \"__LINE__, __FILE__, __DATE__, __TIME__, __STDC__ \"
are in the standard library. If not in the standard library, it is presumed that they can be \"defined, redefined or undefined\". Which interpretation should we take, a) or b) ?

MISRA C Steering Team Answer (7/9/2005)
Option A.
Reserved identifiers are defined by ISO/IEC 9899:1990 sections 7.1.3 Reserved Identifiers, 7.13 Future library directions and 6.8.8 Predefined Macro Names.
Macros in the standard library are examples of reserved identifiers.
Functions in the standard library are examples of reserved identifiers.

Any identifier in the standard library is an example of reserved identifiers.