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| Code Block |
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#define EOF -1
/* // ... */
if (c EOF) {
/* // ... */
}
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In this example, the programmer has mistakenly omitted the comparison operator (see \[[MSC02-A. Avoid errors of omission]\]) from the conditional statement, which should be {{c \!= EOF}}. After macro expansion, the conditional expression is incorrectly evaluated as a binary operation: {{c-1}}. This is syntactically correct, even though it is certainly not what the programmer intended. |
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#define EOF (-1)
/* // ... */
if (c != EOF) {
/* // ... */
}
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Risk Assessment
Failure to use parenthesis around macro definitions 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
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\[[Plum 85|AA. C References#Plum 85]\] 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" |
