# Extra Clang Tools 21.1.8 documentation

## clang-tidy - bugprone-unique-ptr-array-mismatch

# bugprone-unique-ptr-array-mismatch

Finds initializations of C++ unique pointers to non-array type that are initialized with an array.

If a pointer `std::unique_ptr<T>` is initialized with a new-expression `new T[]` the memory is not deallocated correctly. A plain `delete` is used in this case to deallocate the target memory. Instead a `delete[]` call is needed. A `std::unique_ptr<T[]>` uses the correct delete operator. The check does not emit warning if an `unique_ptr` with user-specified deleter type is used.

The check offers replacement of `unique_ptr<T>` to `unique_ptr<T[]>` if it is used at a single variable declaration (one variable in one statement).

Example:

    std::unique_ptr<Foo> x(new Foo[10]); // -> std::unique_ptr<Foo[]> x(new Foo[10]);
    //                     ^ warning: unique pointer to non-array is initialized with array
    std::unique_ptr<Foo> x1(new Foo), x2(new Foo[10]); // no replacement
    //                                   ^ warning: unique pointer to non-array is initialized with array

    D d;
    std::unique_ptr<Foo, D> x3(new Foo[10], d); // no warning (custom deleter used)

    struct S {
      std::unique_ptr<Foo> x(new Foo[10]); // no replacement in this case
      //                     ^ warning: unique pointer to non-array is initialized with array
    };

This check partially covers the CERT C++ Coding Standard rule MEM51-CPP. Properly deallocate dynamically allocated resources However, only the `std::unique_ptr` case is detected by this check.