Annex F (informative) Core undefined behavior [ub]

F.3 [expr]: Expressions [ub.expr]

F.3.22[ub:expr.delete.mismatch]
Specified in: [expr.delete]

Using array delete on the result of a single object new expression has undefined behavior.
[Example 1: int* x = new int; delete[] x; // undefined behavior, allocated using single object new expression — end example]