NAME¶

std::invalid_argument - std::invalid_argument

Synopsis¶

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.

std-invalid argument-inheritance.svg

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)
invalid_argument( const invalid_argument& other ); (3) (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.

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 (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.

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

// Run this code

#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 added
char* was missing
the explanatory strings of they are the same as that of
LWG 471 C++98 std::invalid_argument's the
copies were implementation-defined original std::invalid_argument
object