Labels used to declare variables?

[georgelappies]

Hi all

There seems to be an inconsistency between some text when it comes to declaring labels for variables. Some use the ":" and some not.

For instance are the following two data declaration blocks equivalent?

Code: [Select]

; ----- data declarations -----
i: dw 0 ; set i = 0
A: dw 0
B: dw 0
C: dw 0
D: dw 0

and this one:

Code: [Select]

; ----- data declarations -----
i dw 0 ; set i = 0
A dw 0
B dw 0
C dw 0
D dw 0

Or does the ":" signify some special meaning?

[Frank Kotler]

Hi George,

The two data declarations you show are identical. Essentially, Nasm does not require a colon - it's the same thing with or without. However, there's an exception to this if the label (variable name) is the only thing on the line - what Nasm calls an "orphan-label". This can trigger one of Nasm's "suppressible warnings":
 http://www.nasm.us/xdoc/2.10/html/nasmdoc2.html#section-2.1.24

In earlier versions of Nasm, the "orphan-labels" warning was disabled by default..

Code: [Select]

mov esi, my_var
lodbs ; <-typo!
Nasm would assemble this with no indication of a possible problem. Recent versions have this warning enabled by default, and will warn that this "might be an error". Maybe it's not an error, maybe you intended a label by that name and didn't want a colon on it for reasons of your own. You can disable the warning - "-w-orphan-labels" - either on the command line or in the code (you can have warnings "on" for part of the code and "off" for the rest). Or you can ignore the warning - Nasm will assemble it anyway. Or you can put the colon there. It merely serves as a rudimentary "spell checker".

With the exception of this "label alone on a line" situation, Nasm doesn't care if you've got a colon after it or not. Programmer's choice!

Best,
Frank