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The following scenarios will be diagnosed because either can result in undefined behavior: • Receiving

•  Receiving input from a stream directly following an output to that stream without an intervening call to fflush, fseek, fsetpos, or rewind if the file is not at end-of-file

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•  Outputting to a stream after receiving input from that stream without a call to fseek, fsetpos, or rewind if the file is not at end-of-file

(See also undefined behavior 151 in Annex J of C11.) Consequently, a call to fseek(), fflush(), or fsetpos() is necessary between input and output to the same stream. (See FIO07-C. Prefer fseek() to rewind().)

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