std::runtime_error
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Defined in header <stdexcept> | ||
class runtime_error; | ||
Defines a type of object to be thrown as exception. It reports errors that are due to events beyond the scope of the program and cannot be easily predicted.
All member functions ofstd::runtime_error areconstexpr: it is possible to create and usestd::runtime_error objects in the evaluation of a constant expression.However, | (since C++26) |
Inheritance diagram
Exceptions of typestd::runtime_error are thrown by the following standard library components:
| (since C++20) |
In addition, the following standard exception types are derived fromstd::runtime_error:
| (since C++11) |
| (since C++17) |
| (since C++20) |
Contents |
[edit]Member functions
(constructor) | constructs a newruntime_error object with the given message(public member function) |
operator= | replaces theruntime_error object(public member function) |
std::runtime_error::runtime_error
runtime_error(conststd::string& what_arg); | (1) | (constexpr since C++26) |
runtime_error(constchar* what_arg); | (2) | (constexpr since C++26) |
runtime_error(const runtime_error& other); | (3) | (noexcept since C++11) (constexpr since C++26) |
std::runtime_error thenstd::strcmp(what(), other.what())==0. No exception can be thrown from the copy constructor.Parameters
| what_arg | - | explanatory string |
| other | - | another exception object to copy |
Exceptions
Notes
Because copyingstd::runtime_error is not permitted to throw exceptions, this message is typically stored internally as a separately-allocated reference-counted string. This is also why there is no constructor takingstd::string&&: it would have to copy the content anyway.
Before the resolution ofLWG issue 254, the non-copy constructor can only acceptstd::string. It makes dynamic allocation mandatory in order to construct astd::string object.
After the resolution ofLWG issue 471, a derived standard exception class must have a publicly accessible copy constructor. It can be implicitly defined as long as the explanatory strings obtained bywhat() are the same for the original object and the copied object.
std::runtime_error::operator=
runtime_error& operator=(const runtime_error& other); | (noexcept since C++11) (constexpr since C++26) | |
Assigns the contents with those ofother. If*this andother both have dynamic typestd::runtime_error thenstd::strcmp(what(), other.what())==0 after assignment. No exception can be thrown from the copy assignment operator.
Parameters
| other | - | another exception object to assign with |
Return value
*this
Notes
After the resolution ofLWG issue 471, a derived standard exception class must have a publicly accessible copy assignment operator. It can be implicitly defined as long as the explanatory strings obtained bywhat() are the same for the original object and the copied object.
Inherited fromstd::exception
Member functions
[virtual] | destroys the exception object (virtual public member function of std::exception)[edit] |
[virtual] | returns an explanatory string (virtual public member function of std::exception)[edit] |
[edit]Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_constexpr_exceptions | 202502L | (C++26) | constexpr exception types |
[edit]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 254 | C++98 | the constructor acceptingconstchar* was missing | added |
| LWG 471 | C++98 | the explanatory strings ofstd::runtime_error'scopies were implementation-defined | they are the same as that of the original std::runtime_error object |
