Purpose of Unions in C and C++

Question

I have used unions earlier comfortably; today I was alarmed when I read this post and came to know that this code

union ARGB
{
    uint32_t colour;

    str         


        

Answer 1

Although this is strictly undefined behaviour, in practice it will work with pretty much any compiler. It is such a widely used paradigm that any self-respecting compiler will need to do "the right thing" in cases such as this. It's certainly to be preferred over type-punning, which may well generate broken code with some compilers.