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std::invalid_argument

Defined in header `<stdexcept>`
class invalid_argument;

Defines a type of object to be thrown as exception. It reports errors that arise because an argument value has not been accepted.

This exception is thrown by std::bitset::bitset, and the std::stoi and std::stof families of functions.

Inheritance diagram.

Member functions

(constructor)	constructs a new `invalid_argument` object with the given message (public member function)
operator=	replaces the `invalid_argument` object (public member function)

std::invalid_argument::invalid_argument

invalid_argument( const std::string& what_arg );	(1)
invalid_argument( const char* what_arg );	(2)
	(3)
invalid_argument( const invalid_argument& other );		(until C++11)
invalid_argument( const invalid_argument& other ) noexcept;		(since C++11)

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::invalid_argument then std::strcmp(what(), other.what()) == 0. No exception can be thrown from the copy constructor. (until C++11)

Parameters

what_arg	-	explanatory string
other	-	another exception object to copy

Exceptions

1-2) May throw std::bad_alloc

Notes

Because copying std::invalid_argument 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.

std::invalid_argument::operator=

invalid_argument& operator=( const invalid_argument& other );		(until C++11)
invalid_argument& operator=( const invalid_argument& other ) noexcept;		(since C++11)

Assigns the contents with those of other. If *this and other both have dynamic type std::invalid_argument then std::strcmp(what(), other.what()) == 0 after assignment. No exception can be thrown from the copy assignment operator. (until C++11).

Parameters

other

another exception object to assign with

Return value

*this.

Notes

After 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.

Inherited from std::logic_error

Inherited from std::exception

Member functions

(destructor) [virtual]	destroys the exception object (virtual public member function of `std::exception`)
what [virtual]	returns an explanatory string (virtual public member function of `std::exception`)

Notes

The purpose of this exception type is similar to the error condition std::errc::invalid_argument (thrown in std::system_error from member functions of std::thread) and the related errno constant EINVAL.

Example

#include <bitset>
#include <iostream>
#include <stdexcept>
#include <string>
 
int main()
{
    try
    {
        std::bitset<4>{"012"}; // Throws: only '0' or '1' expected
    }
    catch (std::invalid_argument const& ex)
    {
        std::cout << "#1: " << ex.what() << '\n';
    }
 
    try
    {
        [[maybe_unused]] int f = std::stoi("ABBA"); // Throws: no conversion
    }
    catch (std::invalid_argument const& ex)
    {
        std::cout << "#2: " << ex.what() << '\n';
    }
 
    try
    {
        [[maybe_unused]] float f = std::stof("(3.14)"); // Throws: no conversion
    }
    catch (std::invalid_argument const& ex)
    {
        std::cout << "#3: " << ex.what() << '\n';
    }
}

Possible output:

#1: bitset string ctor has invalid argument
#2: stoi: no conversion
#3: stof: no conversion

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 of `std::invalid_argument`'s copies were implementation-defined	they are the same as that of the original `std::invalid_argument` object

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