binary operators

[dogbert1793]

Consider the code:

unsigned char uc;
cout << "sizeof( unsigned char ) = " << sizeof( uc ) << endl;
cout << "sizeof( ~unsigned char ) = " << sizeof( ~uc ) << endl;

Why is the output:

sizeof( unsigned char ) = 1
sizeof( ~unsigned char ) = 4

and not

sizeof( unsigned char ) = 1
sizeof( ~unsigned char ) = 1

 

[Barry]

Consider the code:

unsigned char uc;
cout << "sizeof( unsigned char ) = " << sizeof( uc ) << endl;
cout << "sizeof( ~unsigned char ) = " << sizeof( ~uc ) << endl;

Why is the output:

sizeof( unsigned char ) = 1
sizeof( ~unsigned char ) = 4

and not

sizeof( unsigned char ) = 1
sizeof( ~unsigned char ) = 1

[std--
4.5 Integral promotions [conv.prom]

3. An rvalue for an integral bit-field (9.6) can be converted to an
rvalue of type int if int can represent all
the values of the bit-field; otherwise, it can be converted to unsigned
int if unsigned int can represent
all the values of the bit-field. If the bit-field is larger yet, no
integral promotion applies to it. If the
bit-field has an enumerated type, it is treated as any other value of
that type for promotion purposes.
--End-std]