MISRA C:2012 Rule 1.4

Emergent language features shall not be used

Description

Rule Definition

Emergent language features shall not be used¹ .

Rationale

Some new language features in the C11 Standard have undefined, unspecified or implementation-defined behavior. These features might also exhibit well-defined behavior that defies developer expectations. Though rule 1.3 and directive 1.1 prohibits undefined and implementation-defined behavior, to avoid well-defined behavior that defies expectations, some language features are summarily discouraged using rule 1.4.

Polyspace Implementation

The rule forbids use of all facilities in Annex K of the C11 Standard about 'Bound-checking interfaces', other than defining __STDC_WANT_LIB_EXT1__ to '0'.

Troubleshooting

If you expect a rule violation but do not see it, refer to Diagnose Why Coding Standard Violations Do Not Appear as Expected.

Examples

Use of Facilities in Annex K of C11 Standard

#define __STDC_WANT_LIB_EXT1__ 1 //Noncompliant
#include <string.h>

void Copying_functions(void) {
    char buf1[10];
    char buf2[10];
    errno_t e;  //Noncompliant
    e = memcpy_s(buf1,sizeof(buf1),buf2,5); //Noncompliant
    e = memmove_s(buf1,sizeof(buf1),buf2,5); //Noncompliant
    e = strcpy_s(buf1,sizeof(buf1),buf2); //Noncompliant
    e = strncpy_s(buf1,sizeof(buf1),buf2,5); //Noncompliant
}

In this example, the macro __STDC_WANT_LIB_EXT1__ is set to 1 so that the type errno_t as defined in the header stdlib.h can be used (in accordance with Annex K of the C11 Standard).

The checker flags both the setting of the macro to 1 and the definition of the errno_t variable, along with other functions from Annex K.

Check Information

Group: Standard C Environment

Category: Required

AGC Category: Required

Version History

Introduced in R2014b

R2024b: Some C11 features previously noncompliant are now compliant

Following MISRA C:2012 Amendment 4, this rule now allows the use of these features:

• The _Atomic type specifier and the facilities provided by <stdatomic.h>

• The _Thread_local storage class specifier and the facilities provided by <threads.h>

R2024a: Some C11 features previously noncompliant are now compliant

Following MISRA C:2012 Amendment 3, this rule now allows the use of these features:

• The _Generic operator

• The _Noreturn specifier

• The <stdnoreturn.h> header file

• The _Alignas alignment specifier

• The _Alignof operator

• The <stdalign.h> header file