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Noncompliant Code Example (Header Guard)
A common but noncompliant practice is to choose a reserved name for use a macro used in a preprocessor conditional guarding which guards against multiple inclusions of a header file. The . While this is a recommended practice, many programs use reserved names as the header guards. Such a name may clash with reserved names defined by the implementation of the C++ standard template library in its headers or with reserved names implicitly predefined by the compiler even when no C++ standard library header is included.
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