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[exception]
17 Language support library [support]
17.9 Exception handling [support.exception]
17.9.3 Class exception [exception]
namespace std {class exception {public:constexpr exception() noexcept; constexpr exception(const exception&) noexcept; constexpr exception& operator=(const exception&) noexcept; constexpr virtual ~exception(); constexpr virtual const char* what() const noexcept; };}
The classexception defines the base class for the types of objects thrown as exceptions by C++ standard library components, and certain expressions, to report errors detected during program execution.
Except where explicitly specified otherwise, each standard library class T that derives from class exception has the following publicly accessible member functions, each of them having a non-throwing exception specification ([except.spec]):
default constructor (unless the class synopsis shows other constructors)
copy constructor
copy assignment operator
The copy constructor and the copy assignment operator meet the following postcondition: If two objects lhs and rhs both have dynamic type T and lhs is a copy of rhs, thenstrcmp(lhs.what(), rhs.what()) is equal to 0.
The what() member function of each such T satisfies the constraints specified for exception::what() (see below).
constexpr exception(const exception& rhs) noexcept; constexpr exception& operator=(const exception& rhs) noexcept;
Postconditions: If *this and rhs both have dynamic type exception then the value of the expression strcmp(what(), rhs.what()) shall equal 0.
constexpr virtual ~exception();
Effects: Destroys an object of classexception.
constexpr virtual const char* what() const noexcept;
Returns: An implementation-defined ntbs, which during constant evaluation is encoded with the ordinary literal encoding ([lex.ccon]).
Remarks: The message may be anull-terminated multibyte string, suitable for conversion and display as awstring ([string.classes], [locale.codecvt]).
The return value remains valid until the exception object from which it is obtained is destroyed or a non-const member function of the exception object is called.