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To guarantee identifiers are unique, you must first determine the number of significant characters recognized by (the most restrictive) compiler you are usingused must be determined. This assumption must be documented in the code.
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Restriction of the significance of an external name to fewer than 255 characters in the standard (considering each universal character name or extended source character as a single character) is an obsolescent feature that is a concession to existing implementations. Therefore, it is not necessary to comply with this restriction, as long as your the identifiers are unique and your the assumptions concering the number of significant characters is documented.
Non-Compliant Code Example
Assuming your the compiler implements the minimum requirements for signficant characters required by the standard, the following examples are non-compliant:
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