# std::exception::exception

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< cpp‎ | error‎ | exception

| (1) |
exception() throw(); |  | (until C++11)
exception() noexcept; |  | (since C++11) (constexpr since C++26)
| (2) |
exception( const exception& other ) throw(); |  | (until C++11)
exception( const exception& other ) noexcept; |  | (since C++11) (constexpr since C++26)

Constructs new exception object.

1) Default constructor. what() returns an implementation-defined string.
2) Copy constructor. Initializes the contents with those of other. If *this and other both have dynamic type `std::exception` then std::strcmp (what(), other.what()) == 0.

### Parameters

other | - | another exception to assign the contents of

### Notes

Because copying `std::exception` is not permitted to throw exceptions, when derived classes (such as std::runtime_error) have to manage a user-defined diagnostic message, it is typically implemented as a copy-on-write string.

The Microsoft implementation includes non-standard constructors taking strings thus allowing instances to be thrown directly with a meaningful error message. The nearest standard equivalents are std::runtime_error or std::logic_error.

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 471 | C++98 | there is no requirement on what() of the exception copy | added

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