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In this noncompliant code example, EOF END_OF_FILE is defined as -1. The macro replacement list consists of a unary negation operator, followed by an integer literal 1.

#define EOFEND_OF_FILE -1
/* ... */
if (getchar() EOF) {
   /* ... */
}

In this example, the programmer has mistakenly omitted the comparison operator from the conditional statement, which should be getchar() != EOFEND_OF_FILE. (See 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 DCL00-C. Const-qualify immutable objects.

Parenthesizing the -1 in the declaration of EOF END_OF_FILE ensures that the macro expansion is evaluated correctly.

#define EOFEND_OF_FILE (-1)

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 END_OF_FILE 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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