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DCL40-EX0: No diagnostic need be issued if a declaration that is incompatible with the definition occurs in a translation unit that does not contain any definition or uses of the function or object other than possibly additional declarations. This code is not in compliance with Such code violates MSC12-C. Detect and remove code that has no effect or MSC13-C. Detect and remove unused values, but it does not cause undefined behavior.
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