Macro replacement lists should be parenthesized to protect any lower-precedence operators from the surrounding expression. See also guidelines PRE00-C. Prefer inline or static functions to function-like macros and PRE01-C. Use parentheses within macros around parameter names.
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This compliant solution violates guideline PRE00-C. Prefer inline or static functions to function-like macros. Consequently, this solution would be better implemented as an inline function.
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In this example, the programmer has mistakenly omitted the comparison operator (see MSC02-C. Avoid errors of omission) from the conditional statement, which should be getchar() != EOF. (See guideline MSC02-C. Avoid errors of omission.) After macro expansion, the conditional expression is incorrectly evaluated as a binary operation: getchar()-1. This is syntactically correct, even though it is certainly not what the programmer intended. Note that this example also violates guideline DCL00-C. Const-qualify immutable objects.
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Once this modification is made, the noncompliant code example no longer compiles because the macro expansion results in the conditional expression getchar() (-1), which is no longer syntactically valid. Note that there must be a space after EOF because, otherwise, it becomes a function-like macro (and one that is incorrectly formed , because -1 cannot be a formal parameter).
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In this compliant solution, the macro definition is replaced with an enumeration constant in compliance with guideline DCL00-C. Const-qualify immutable objects. In addition, since EOF is a reserved macro defined in the <stdio.h> header, the compliant solution must also use a different indentifier in order to comply with guideline DCL37-C. Do not use identifiers that are reserved for the implementation.
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Recommendation | Severity | Likelihood | Remediation Cost | Priority | Level |
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PRE02-C | medium | probable | low | P12 | L1 |
Automated Detection
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Related Vulnerabilities
Search for vulnerabilities resulting from the violation of this rule on the CERT website.
Other Languages
Related Guidelines
This rule appears in the C++ Secure Coding Standard as : PRE02-CPP. Macro replacement lists should be parenthesized.
Bibliography
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\[[ISO/IEC 9899:1999|AA. Bibliography#ISO/IEC 9899-1999]\] Section 6.10, "Preprocessing directives," and Section 5.1.1, "Translation environment" \[[ISO/IEC PDTR 24772|AA. Bibliography#ISO/IEC PDTR 24772]\] "JCW Operator precedence/Order of Evaluation", "NMP Pre-processor Directions" \[[Plum 851985|AA. Bibliography#Plum 85]\] Rule 1-1 \[[Summit 052005|AA. Bibliography#Summit 05]\] Question 10.1 |
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