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Code that is executed but does not perform any action, or has an unintended effect, most likely results from a coding error and can result in can cause unexpected behavior. Statements or expressions that have no effect should be identified and removed from code. Most modern compilers can warn about code that has no effect in many cases. (See recommendation MSC00-C. Compile cleanly at high warning levels.)

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

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

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

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

...

In this example, a pointer increment and then a dereference occursoccur. However, the dereference has no effect.

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

Compliant Solution (Dereference)

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

If the intent was to increment the value referred to by p, then parentheses can be used to ensure p is dereferenced and then incremented. (See recommendation EXP00-C. Use parentheses for precedence of operation.)

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++;

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ISO/IEC TR 24772 "BRS Leveraging human experience," "BVQ Unspecified Functionalityfunctionality," "KOA Likely incorrect expressions," and "XYQ Dead and Deactivated Codedeactivated code"

MISRA Rule 14.1 and Rule 14.2

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Sources

[Coverity 2007]

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