[Windows programming] bool, bool, and variant_bool in C ++

Next, we will continue to discuss the bool variable. There are several common types of bool variables in Windows: lower-case bool, upper-case bool, and variant_bool.

 

LowercaseBoolIt is a boolean type defined in the C ++ standard. Different compilers process different types of data.BoolSetOne byte. LowercaseTrueAndFalseIt is also a standard-defined keyword in C ++.

 

UppercaseBoolIs a boolean type defined in windows, essentiallyIntThe Windows header file is defined as follows:

 

Typedef int bool;

# Define true 1
# Define false 0

Variant_boolIs a boolean type used by COM, which is essentiallyShortType:

 

Typedef short variant_bool;

# Define variant_true (variant_bool)-1)

# Define variant_false (variant_bool) 0)

It can be seen that the bool type in 3 has different lengths, and the values of true and false are also different. You must note when converting each other.