Unions are a specialized struct within which all members occupy overlapping memory.
union U {
int a;
short b;
float c;
};
U u;
//Address of a and b will be equal
(void*)&u.a == (void*)&u.b;
(void*)&u.a == (void*)&u.c;
//Assigning to any union member changes ...
Unions are useful for minimizing memory usage for exclusive data, such as when implementing mixed data types.
struct AnyType {
enum {
IS_INT,
IS_FLOAT
} type;
union Data {
int as_int;
float as_float;
} value;
AnyType(int i) : type...
union U {
int a;
short b;
float c;
};
U u;
u.a = 10;
if (u.b == 10) {
// this is undefined behavior since 'a' was the last member to be
// written to. A lot of compilers will allow this and might issue a
// warning, but the result will be "as expected"; thi...
