GLOBAL and SHARED variables

[ervin]

Hi everyone.

I am trying to write a routine to print large sprites using small tile pieces.
Anyway, I am having some problems with GLOBAL and SHARED variables.

I've reduced the code to a very basic example.

Code: Select all

OPTION EXPLICIT ON

DIM a AS BYTE

PROCEDURE testProc
	SHARED a
	PRINT a
END PROCEDURE

a=8
CALL testProc

On the CPC target, this prints 8, which is the expected result.

However, this code:

Code: Select all

OPTION EXPLICIT ON

GLOBAL a AS BYTE

PROCEDURE testProc
	PRINT a
END PROCEDURE

a=8
CALL testProc

Causes a compilation error:

undefined variable (OPTION EXPLICIT ON) (a)

If I set OPTION EXPLICIT OFF, the program compiles, and works as expected.
But that removes the desired benefits of using OPTION EXPLICIT.

Does GLOBAL only work when OPTION EXPLICIT is OFF?

[ervin]

I solved it!

Code: Select all

OPTION EXPLICIT ON

DIM a AS BYTE
GLOBAL a

PROCEDURE testProc
	PRINT a
END PROCEDURE

a=8
CALL testProc

[spotlessmind1975]

Hi ervin, and welcome!

undefined variable (OPTION EXPLICIT ON) (a)

This error should be correct, since the GLOBAL command allows you to tell ugBASIC to consider a variable as "global" but the instruction neither initializes the variable nor creates it. This means that there is no "promise" on the type. In this topic, I asked if this behaviour is the expected one. I couldn't come up with an answer. In the meantime this semantics spread, so in the end I let the behavior remain as it is.

[ervin]

Makes sense, thanks!
(by the way, I'm "poppichicken" that has been reporting bugs on github).