Name
defined operator — Tests whether a macro is defined
Synopsis
defined(identifier
) definedidentifier
The unary operator defined(
identifier
)
(also written as defined
identifier
, without the parentheses)
evaluates to 1
if
identifier
is a known macro name at the
point of the defined
operator, or
0
if it is not known. The operator
is evaluated only in the argument to an #if
or #elif
directive.
The behavior is undefined if the defined
operator is used in any other way,
or if the token defined
results
from macro expansion.
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