std::make_signed

 

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Defined in header <type_traits>
template< class T > struct make_signed;		(since C++11)

If T is an integral (except bool) or enumeration type, provides the member typedef type which is the signed integer type corresponding to T, with the same cv-qualifiers.

If T is signed or unsigned char, short, int, long, long long, the signed type from this list corresponding to T is provided.

If T is an enumeration type or char, wchar_t, char8_t (since C++20), char16_t, char32_t, the signed integer type with the smallest rank having the same sizeof as T is provided.

Otherwise, the behavior is undefined.	(until C++20)
Otherwise, the program is ill-formed.	(since C++20)

The behavior of a program that adds specializations for make_signed is undefined.

Member types

Name	Definition
type	the signed integer type corresponding to T

Helper types

template< class T > using make_signed_t = typename make_signed<T>::type;		(since C++14)

Example

Run this code

#include <iostream>
#include <type_traits>
 
int main() {
    typedef std::make_signed<unsigned char>::type char_type;
    typedef std::make_signed<unsigned int>::type int_type;
    typedef std::make_signed<volatile unsigned long>::type long_type;
 
    bool ok1 = std::is_same<char_type, signed char>::value;
    bool ok2 = std::is_same<int_type, signed int>::value;
    bool ok3 = std::is_same<long_type, volatile signed long>::value;
 
    std::cout << std::boolalpha
    << "char_type is 'signed char'?          : " << ok1 << '\n'
    << "int_type  is 'signed int'?           : " << ok2 << '\n'
    << "long_type is 'volatile signed long'? : " << ok3 << '\n';
}

Output:

char_type is 'signed char'?          : true
int_type  is 'signed int'?           : true
long_type is 'volatile signed long'? : true

See also

is_signed (C++11)	checks if a type is a signed arithmetic type (class template)
is_unsigned (C++11)	checks if a type is an unsigned arithmetic type (class template)
make_unsigned (C++11)	makes the given integral type unsigned (class template)