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Use parenthesis parentheses around any macro definition replacement list that contains operators.

Non-Compliant Coding Example

In this non-compliant coding example, EOF is defined as -1. This The macro definition replacement list consists of a unary negation operator '-' followed by an integer literal '1'.

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Once this modification is made, the non-compliant code example no longer compiles as the macro expansion results in the conditional expression c (-1), which is no longer syntactically valid.

Compliant Solution

The following compliant solution uses parenthesis parentheses around the macro definition replacement list and adds the (previously omitted) comparison operator.

#define EOF (-1)
/* ... */
if (c != EOF) {
   /* ... */
}

Risk Assessment

Failure to use parenthesis parentheses around macro definitions replacement lists that contain operators can result in unintended program behavior.

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

References

\[[Plum 85|AA. C References#Plum 85]\] Rule 1-1
\[[ISO/IEC 9899-1999|AA. C References#ISO/IEC 9899-1999]\] Section 6.10, "Preprocessing directives," and Section 5.1.1, "Translation environment"