std::invalid_argument
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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 bystd::bitset::bitset, and thestd::stoi andstd::stof families of functions.
All member functions ofstd::invalid_argument areconstexpr: it is possible to create and usestd::invalid_argument objects in the evaluation of a constant expression.However, | (since C++26) |
Inheritance diagram
Contents |
[edit]Member functions
(constructor) | constructs a newinvalid_argument object with the given message(public member function) |
operator= | replaces theinvalid_argument object(public member function) |
std::invalid_argument::invalid_argument
invalid_argument(conststd::string& what_arg); | (1) | (constexpr since C++26) |
invalid_argument(constchar* what_arg); | (2) | (constexpr since C++26) |
invalid_argument(const invalid_argument& other); | (3) | (noexcept since C++11) (constexpr since C++26) |
std::invalid_argument 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::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 takingstd::string&&: it would have to copy the content anyway.
Before the resolution ofLWG issue 254, the non-copy constructor can only acceptstd::string. It makes dynamic allocation mandatory in order to construct astd::string object.
After the resolution ofLWG 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 bywhat() 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) (constexpr since C++26) | |
Assigns the contents with those ofother. If*this andother both have dynamic typestd::invalid_argument 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
After the resolution ofLWG 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 bywhat() are the same for the original object and the copied object.
Inherited fromstd::logic_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
The purpose of this exception type is similar to the error conditionstd::errc::invalid_argument (thrown instd::system_error from member functions ofstd::thread) and the related errno constantEINVAL.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_constexpr_exceptions | 202502L | (C++26) | constexpr exception types |
[edit]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_argumentconst& ex){std::cout<<"#1: "<< ex.what()<<'\n';} try{[[maybe_unused]]int f=std::stoi("ABBA");// Throws: no conversion}catch(std::invalid_argumentconst& ex){std::cout<<"#2: "<< ex.what()<<'\n';} try{[[maybe_unused]]float f=std::stof("(3.14)");// Throws: no conversion}catch(std::invalid_argumentconst& ex){std::cout<<"#3: "<< ex.what()<<'\n';}}
Possible output:
#1: bitset string ctor has invalid argument#2: stoi: no conversion#3: stof: no conversion
[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 acceptingconstchar* was missing | added |
| LWG 471 | C++98 | the explanatory strings ofstd::invalid_argument'scopies were implementation-defined | they are the same as that of the original std::invalid_argument object |
