Difference between bool and uint32 :1

Development Programming & Scripting
1

As the title, the declaration uint32 blabla:1 declares a variable of type uint32, and the size of the variable is 1 bit, right? If that so, then don’t we declare it as a bool?

Also, uint32 : 1, uint16 : 1, uint8 : 1 all have size 1 bit right?

Thanks,

David

2

Hey WCL,

The number after uint specifies the Size of the Integer
uint32 ist an unsigned integer with 32 Bit so it can hold values from 0 to 2^32
The same goes for uint16 (16 Bit) and uint8 (8 Bit)

A bools Size should be 8 Bit so 1 Byte, because it only uses 1 Bit, but to be “adressable” the size of a variable should be at least 8 Bit.
I heard that in some Compilers bool are 4 Byte long (32 Bit) but I don’t know if this is TRUE or FALSE (hehe)

I hope I could answer your question :))

3

You probably should declare it as a bool.

The syntax uint32:1 declares the variable as a bit field, a set of bits within a bigger integer type. bool declares your variable as a tiny integer. There are subtle, compiler-dependent implications of a bit field, but these have a negligible impact on your performance. Bit fields don’t support pointers nor non-const references, which may or may not matter to you. Ultimately, the most important thing is to choose the version that is easiest to read.

4

Thanks! It’s clearer right now.

5

Thanks, dbuchoff! Are there any textbooks which I can delve into more? I only read c++ Primer plus 5th edition and there’s only a brief introduction.

6

C++ is a huge language, and frankly it’s not worth learning the whole thing just for Unreal development. I liked A Tour of C++. I also like Effective Modern C++, but wouldn’t recommend it, since you’re not going to be taking advantage of many language features (e.g. braced initializers, since in Unreal code, you never call the constructor directly; e.g. references, since most code is going to pass UObjects around by pointer). Also, most books are going to use standard C++ libraries (like std::vector), which should not be used when a more Unreal-ish alternative exists (like TArray).

I highly recommend only learning language features when you need them or see them in code you are working with.

2 Likes
7

Much thanks! I will take your advice seriously.