std::length_error
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Defined in header <stdexcept> | ||
class length_error; | ||
Defines a type of object to be thrown as exception. It reports errors that result from attempts to exceed implementation defined length limits for some object.
This exception is thrown by member functions ofstd::basic_string andstd::vector::reserve.
All member functions ofstd::length_error areconstexpr: it is possible to create and usestd::length_error objects in the evaluation of a constant expression.However, | (since C++26) |
Inheritance diagram
Contents |
[edit]Member functions
(constructor) | constructs a newlength_error object with the given message(public member function) |
operator= | replaces thelength_error object(public member function) |
std::length_error::length_error
length_error(conststd::string& what_arg); | (1) | (constexpr since C++26) |
length_error(constchar* what_arg); | (2) | (constexpr since C++26) |
length_error(const length_error& other); | (3) | (noexcept since C++11) (constexpr since C++26) |
std::length_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::length_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::length_error::operator=
length_error& operator=(const length_error& other); | (noexcept since C++11) (constexpr since C++26) | |
Assigns the contents with those ofother. If*this andother both have dynamic typestd::length_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::logic_error
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::length_error'scopies were implementation-defined | they are the same as that of the original std::length_error object |
[edit]See also
| changes the number of characters stored (public member function of std::basic_string<CharT,Traits,Allocator>)[edit] |
