std::format_error

std::format_error::format_error

format_error( const std::string & what_arg ) ;	(1)
format_error( const char* what_arg );	(2)
format_error( const format_error& other ) noexcept ;	(3)

Parameters

what_arg	-	explanatory string
other	-	another exception object to copy

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&&

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 ;

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

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 by what()

#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());
    }
}

format error: failed to parse format-spec