std::format_error
| Localization library | |||||||||||||||||||||||||
| Regular expressions library(C++11) | |||||||||||||||||||||||||
| Formatting library(C++20) | |||||||||||||||||||||||||
| Null-terminated sequence utilities | |||||||||||||||||||||||||
| Byte strings | |||||||||||||||||||||||||
| Multibyte strings | |||||||||||||||||||||||||
| Wide strings | |||||||||||||||||||||||||
| Primitive numeric conversions | |||||||||||||||||||||||||
| |||||||||||||||||||||||||
| Text encoding identifications | |||||||||||||||||||||||||
| |||||||||||||||||||||||||
| Standard format specification | ||||
| Formatting functions | ||||
(C++20) | ||||
(C++20) | ||||
(C++20) | ||||
(C++20) | ||||
(C++20) | ||||
(C++20) | ||||
| Format strings | ||||
(C++20)(C++20)(C++20) | ||||
(C++26) | ||||
| Formatting concepts | ||||
(C++23) | ||||
| Formatter | ||||
(C++20) | ||||
(C++23) | ||||
(C++23) | ||||
(C++23) | ||||
(C++20)(C++20)(C++20) | ||||
(C++20)(C++20)(C++20) | ||||
(C++23) | ||||
(C++23) | ||||
| Formatting arguments | ||||
(C++20) | ||||
(C++20) | ||||
(C++20)(C++20)(C++20) | ||||
(C++20)(deprecated in C++26) | ||||
(C++20)(C++20) | ||||
| Format error | ||||
format_error (C++20) |
Defined in header <format> | ||
class format_error:public runtime_error | (since C++20) | |
Defines the type of exception object thrown to report errors in the formatting library.
All member functions ofstd::format_error areconstexpr: it is possible to create and usestd::format_error objects in the evaluation of a constant expression.However, | (since C++26) |
Inheritance diagram
Contents |
[edit]Member functions
(constructor) | constructs a newformat_error object with the given message(public member function) |
operator= | replaces theformat_error object(public member function) |
std::format_error::format_error
format_error(conststd::string& what_arg); | (1) | (constexpr since C++26) |
format_error(constchar* what_arg); | (2) | (constexpr since C++26) |
format_error(const format_error& other)noexcept; | (3) | (constexpr since C++26) |
std::format_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::format_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.
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::format_error::operator=
format_error& operator=(const format_error& other)noexcept; | (constexpr since C++26) | |
Assigns the contents with those ofother. If*this andother both have dynamic typestd::format_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
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::runtime_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]Example
#include <format>#include <print>#include <string_view>#include <utility> int main(){try{auto x13{37};auto args{std::make_format_args(x13)};std::ignore=std::vformat("{:()}", args);// throws}catch(const std::format_error& ex){std::println("{}", ex.what());}}
Possible output:
format error: failed to parse format-spec
