std::format_error - cppreference.com (original) (raw)

| | | | | ------------------------------------------- | | ------------- | | class format_error : public runtime_error | | (since C++20) |

Defines the type of exception object thrown to report errors in the formatting library.

Inheritance diagram

Contents

• 1 Member functions
• 2 std::format_error::format_error
  • 2.1 Parameters
  • 2.2 Exceptions
  • 2.3 Notes
• 3 std::format_error::operator=
  • 3.1 Parameters
  • 3.2 Return value
  • 3.3 Notes
• 4 Inherited from std::runtime_error
• 5 Inherited from std::exception
  • 5.1 Member functions
  • 5.2 Notes
  • 5.3 Example
  • 5.4 See also

[edit] Member functions

| | constructs a new format_error object with the given message (public member function) | | ---------------------------------------------------------------------------------------- | | | replaces the format_error object (public member function) |

std::format_error::format_error

1. Constructs the exception object with what_arg as explanatory string. After construction, std::strcmp(what(), what_arg.c_str()) == 0.

2. Constructs the exception object with what_arg as explanatory string. After construction, std::strcmp(what(), what_arg) == 0.

3. Copy constructor. If *this and other both have dynamic type std::format_error then std::strcmp(what(), other.what()) == 0. No exception can be thrown from the copy constructor.

Parameters

Exceptions

Notes

Because copying std::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 taking std::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 by what() 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 of other. If *this and other both have dynamic type std::format_error then std::strcmp(what(), other.what()) == 0 after assignment. No exception can be thrown from the copy assignment operator.

Parameters

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 by what() are the same for the original object and the copied object.

Inherited from std::exception

Member functions

| | destroys the exception object (virtual public member function of std::exception) [edit] | | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | returns an explanatory string (virtual public member function of std::exception) [edit] |

[edit] Notes

[edit] Example

Possible output:

format error: failed to parse format-spec

[edit] See also