Removing the infinite loop guard in the bootsector does not prevent qemu from executing it about os-tutorial

[jlagarespo]

QEMU would just continue running whatever there is in memory after the bootsector. Which is zeros. Or garbage data. Once it has gone over all the zeroes of the bootsect it finds the magic number. Let's dissasemble the magic number. What does it do?

push bp
stosb

and so we push bp to the stack and issue the stosb instruction(which by having SI and DI undefined, we are not sure what is it doing). Then we continue running. Likely we find more zeroes. Or maybe BIOS code all over the place. The behaviour is undefined. Probably just running up in memory forever.
Why would any warning or error be issued by QEMU?
As you yourself said, QEMU is not a wizard that knows where the bootsector stops, so how could it know when(or why) to throw a warning?
It just runs what is in memory. Simple enough, that's how computers work.

Hope that awnsered your question :)

[Teln0]

Ive noticed that nasm reacts weirdly to errors, by just "loading the back up of the previous version". I dont know if thats true, just a feeling

[ljleb]

@Teln0 even if that would be the case, I don't know how qemu would find about a previous version. I would change the name of the boot sector file, and still get similar results.

[ljleb]

Simple and clear. Thanks @jlagarespo!