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This recommendation is related to MSC07-C. Detect and remove dead code.

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Noncompliant Code Example (Assignment)

In this example, the comparison of a to b has no effect.

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This is likely a case of the programmer mistakenly using the equals operator == instead of the assignment operator =.

Compliant Solution (Assignment)

The assignment of b to a is now properly performed.

int a;
int b;
/* ... */
a = b;

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Noncompliant Code Example (Dereference)

In this example, p is incremented and then dereferenced. However, *p has no effect.

int *p;
/* ... */
*p++;

Compliant Solution (Dereference)

Correcting this example depends on the intent of the programmer. For instance, if dereferencing p was a mistake, then p should not be dereferenced.

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int *p;
/* ... */
(*p)++;

Compliant Solution (Memory Mapped Devices)

Another possibility is that p is being used to reference a memory-mapped device. In this case, the variable p should be declared as volatile.

volatile int *p;
/* ... */
(void) *p++;

Risk Assessment

The presence of code that has no effect can indicate logic errors that may result in unexpected behavior and vulnerabilities.

Automated Detection

The LDRA tool suite V 7.6.0 is able to can detect violations of this recommendation.

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The Coverity Prevent NO_EFFECT checker finds statements or expressions that do not accomplish anything, or statements that perform an unintended action.

Related Vulnerabilities

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

References

\[[Coverity 07|AA. C References#Coverity 07]\]
\[[ISO/IEC PDTR 24772|AA. C References#ISO/IEC PDTR 24772]\] "BRS Leveraging human experience," "BVQ Unspecified Functionality," "KOA Likely incorrect expressions," and "XYQ Dead and Deactivated Code"
\[[MISRA 04|AA. C References#MISRA 04]\] Rule 14.1 and Rule 14.2

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      13. Miscellaneous (MSC)       MSC13-A. Detect and remove unused values Image Added