LANG.ERRCODE.NOTEST : Missing Test of Error Code

The code calls a function that sets errno to non-zero on failure, but does not subsequently check whether errno is equal to zero.

The functions that are subject to this checking are specified using the ERRNO_SETTING_FUNCTIONS configuration parameter.

To specify that function f() sets errno and should be subject to checking for this class, add a new ERRNO_SETTING_FUNCTIONS rule to your configuration file.

ERRNO_SETTING_FUNCTIONS += f

To exclude a function from checking for this class, comment out the corresponding ERRNO_SETTING_FUNCTIONS rule.

ERRNO_SETTING_FUNCTIONS is also used by the Inappropriate Test of Error Code warning class.

Properties

Class Name

Missing Test of Error Code

Significance

style

Mnemonic

LANG.ERRCODE.NOTEST

Categories

MisraC2023	MisraC2023:22.9	The value of errno shall be tested against zero after calling an errno-setting-function
	MisraC2023:D.4.7	If a function returns error information, then that error information shall be tested
Misra2012	Misra2012:22.9	The value of errno shall be tested against zero after calling an errno-setting-function
	Misra2012:D.4.7	If a function returns error information, then that error information shall be tested
Misra2004	Misra2004:16.10	If a function returns error information, then that error information shall be tested
AUTOSARC++14	AUTOSARC++14:M0-3-2	If a function generates error information, then that error information shall be tested.
MisraC++2008	MisraC++2008:0-3-2	If a function generates error information, then that error information shall be tested.
TS17961	TS17961:5.24-inverrno	5.24. Incorrectly setting and using errno
CERT-C	CERT-C:ERR33-C	Detect and handle standard library errors
	CERT-C:POS54-C	Detect and handle POSIX library errors

Availability

Available for C and C++.

Enabling

Checks for this warning class are disabled by default. To enable them, add the following WARNING_FILTER rule to the project configuration file.

WARNING_FILTER += allow class="Missing Test of Error Code"

Example

#include <errno.h>
#include <stdio.h>

int compare_to_zero(FILE *fp){

  (void) ftell(fp);                /* 'Missing Test of Error Code' warning issued here
                                    * - errno is not checked between return from this call and the next call to ftell()
                                    */

  (void) ftell(fp);                                   /* ok: immediately followed by check errno!=0 */
  if (errno != 0){ return 1; }

  (void) ftell(fp);                                   /* ok: immediately followed by check errno==0 */
  if (errno == 0) {  }
  else {return 1;}

  (void) ftell(fp);                /* 'Missing Test of Error Code' warning issued here
                                    * - following check errno>0 is not a test for equality with zero
                                    */
  if (errno > 0){ return 1; }

  return 0;
}

int compare_to_nonzero(FILE *fp){
  (void) ftell(fp);                /* 'Missing Test of Error Code' warning issued here
                                    * - following check errno==15 is not a test for equality with zero
                                    */
  if (errno == 15){ return 1; }
  return 0;
}

int not_all_paths(FILE *fp, int i){
  (void) ftell(fp);                /* 'Missing Test of Error Code' warning issued here
                                    * - errno is not checked when i!=100
                                    */
  if (i == 100){
    if (errno!=0) {return 1;}
  }
  return 0;
}

Relevant Configuration File Parameters

The following configuration file parameters affect checks for this warning class.