OSDev.org

Posted: **Sun Jul 03, 2011 2:44 pm**

I am trying to use uninitialized variables in my os but can't figure out how. A sample of the code I have so far is:

22: mov test,0xDE
23: section .bss
24: test: resb 1

When I build it using

nasm -f elf -o load.o load.s

, it outputs:

src/load.s:22: error: invalid combination of opcode and operands

I've tried adding square brackets but it doesn't work.

Posted: **Sun Jul 03, 2011 4:10 pm**

jfl wrote:I've tried adding square brackets but it doesn't work.

I add square brackets and nasm tell exactly the issue:

error: operation size not specified

The solution to this mystery error message is specify the operation size.

mov byte [test], 0xDE

ps: test is not a good name for variable label.

Posted: **Mon Jul 04, 2011 12:27 am**

bluemoon wrote:ps: test is not a good name for variable label.

...because "test" is an x86 instruction.

Asm uninitialized data