LANG.STRUCT.SE.DEC : Side Effects in Expression with Decrement

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An expression that contains a pre-decrement or post-decrement operation (--) has one or more other side-effects.

For the purposes of this check:

Function calls are always considered to contain side-effects unless one or more of the following is true:

the function is declared with GNU __attribute__((const)) or __attribute__((pure)), or
the function name matches a SIDE_EFFECT_FREE_FUNCTIONS rule.

All sub-expressions of the expression are checked, regardless of whether or not they will be evaluated.

Class Name

Side Effects in Expression with Decrement

Significance

style

Mnemonic

LANG.STRUCT.SE.DEC

Categories

MisraC2023	MisraC2023:13.3	A full expression containing an increment (++) or decrement (--) operator should have no other potential side effects other than that caused by the increment or decrement operator
Misra2012	Misra2012:13.3	A full expression containing an increment (++) or decrement (--) operator should have no other potential side effects other than that caused by the increment or decrement operator
Misra2004	Misra2004:12.13	The increment (++) and decrement (--) operators should not be mixed with other operators in an expression
AUTOSARC++14	AUTOSARC++14:M5-2-10	The increment (++) and decrement (--) operators shall not be mixed with other operators in an expression.
MisraC++2008	MisraC++2008:5-2-10	The increment ( ++ ) and decrement ( -- ) operators should not be mixed with other operators in an expression.
CERT-C	CERT-C:EXP30-C	Do not depend on the order of evaluation for side effects
	CERT-C:PRE31-C	Avoid side effects in arguments to unsafe macros
CERT-CPP	CERT-CPP:EXP50-CPP	Do not depend on the order of evaluation for side effects
JPL	JPL:19	Do not use expressions with side effects.

Availability

Available for C and C++.

Enabling

Checks for this warning class are disabled by default, and require the unnormalized C ASTs for the project. To enable them, add the following WARNING_FILTER rule and RETAIN_UNNORMALIZED_C_AST specification to the project configuration file.

RETAIN_UNNORMALIZED_C_AST = Yes
WARNING_FILTER += allow class="Side Effects in Expression with Decrement"

Note that retaining the unnormalized ASTs will increase the disk space used to store the project representation, and may make the analysis take longer.

int f(int x);

int lang_struct_se_dec(int a){
    int i;

    i = a--;                    /* 'Side Effects in Expression with Decrement' warning issued here */
    if (a){
      i--;                                                        /* no additional side effects */
    }
    a = f(--i);                 /* 'Side Effects in Expression with Decrement' warning issued here
                                 *  - a function call is always considered to be a side effect
                                 */
    if (a + f(1)){            
        i = (1 == 1) ? 2 : a--; /* 'Side Effects in Expression with Decrement' warning issued here
                                 * - even though the decrement will not be executed
                                 * ('Unreachable Computation' warning also issued here)
                                 */
    }
    return i + a;
}

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

LANG.STRUCT.SE.DEC : Side Effects in Expression with Decrement

Summary

Properties

Example

Relevant Configuration File Parameters