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The presence of unused values may indicate significant logic errors. To prevent such errors, unused values should be identified and removed from code.

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This recommendation is a specific case of MSC12-C. Detect and remove code that has no effect or is never executed.

Noncompliant Code Example

Wiki MarkupIn this example, {{p2}} is assigned the value returned by {{bar()}}, but that value is never used. Note this example assumes that {{foo()}} and {{bar()}} return valid pointers in compliance with \[[DCL30-C]\]pointers (see DCL30-C. Declare objects with appropriate storage durations).

int *p1,;
int *p2;
p1 = foo();
p2 = bar();

if (baz()) {
   return p1;
}
else {
    p2 = p1;
}
return p2;

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Compliant Solution

This example can be corrected corrected in many different ways, depending on the intent of the programmer. In this compliant solution, p2 is initialized to NULL rather than the result of bar()found to be extraneous. The calls to bar() and baz() can be removed if they do not produce any side effects.

int
int *p1, *p2;
p1 = foo();

p2/* =Removable NULL;

if(baz())
   return p1;
else
    p2 = p1;
return p2;

Risk Assessment

 bar() does not produce any side effects */
(void)bar();

/* Removable if baz() does not produce any side effects */
(void)baz();
return p1;

Exceptions

Risk Assessment

Unused The presence of unused values may indicate significant logic errors.

Automated Detection

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Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERTwebsite CERT website.

References

*Coverity 07 Section 6.1.20, "UNUSED_VALUE"

Related Guidelines

Bibliography

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Image Added Image Added Image AddedReferences
Coverity 07 Coverity Prevent? User's Manual (3.3.0) (2007).