According to the C Standard, a constraint is a restriction, either syntactic or semantic, by which the exposition of language elements is to be interpreted [ISO/IEC 9899:2011]. Despite the similar terms, a runtime-constraint is not a kind of constraint.
Violating any shall statement within a Constraint clause in the C standard requires an implementation to issue a diagnostic message, the C Standard, 5.1.1.3 [ISO/IEC 9899:2011] states:
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