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 of std::basic_string and std::vector::reserve.
All member functions ofstd::length_error are constexpr: it is possible to create and use std::length_error objects in the evaluation of a constant expression.
However, std::length_error objects generally cannot be constexpr, because any dynamically allocated storage must be released in the same evaluation of constant expression.
Inheritance diagram
[edit] Member functions constructs a newlength_error object with the given message
length_error object
length_error( const char* what_arg );
(2) (constexpr since C++26)length_error( const length_error& other );
(3) (noexcept since C++11)Constructs the exception object with
what_argas explanatory string. After construction,
std::strcmp(what(), what_arg.c_str()) == 0.
2)Constructs the exception object with
what_argas explanatory string. After construction,
std::strcmp(what(), what_arg) == 0.
3)Copy constructor. If
*thisand
otherboth have dynamic type
std::length_error
then
std::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 NotesBecause copying std::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 taking std::string&&: it would have to copy the content anyway.
Before the resolution of LWG issue 254, the non-copy constructor can only accept std::string. It makes dynamic allocation mandatory in order to construct a std::string object.
After the resolution of LWG 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 by what() are the same for the original object and the copied object.
length_error& operator=( const length_error& other );
(noexcept since C++11)Assigns the contents with those of other. If *this and other both have dynamic type std::length_error then std::strcmp(what(), other.what()) == 0 after assignment. No exception can be thrown from the copy assignment operator.
*this
NotesAfter the resolution of LWG 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 by what() are the same for the original object and the copied object.
std::exception) [edit] returns an explanatory string
std::exception) [edit] [edit] Notes [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 accepting const char* was missing added LWG 471 C++98 the explanatory strings ofstd::length_error's
std::length_error object [edit] See also changes the number of characters stored
std::basic_string<CharT,Traits,Allocator>) [edit]
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