Assume

[clive]

Is it OK to use:

Code Select Expand

lea eax,MyStruct
assume eax:ptr Whatever

; do stuff here

call SomeWinAPICallHere ; <<<<<<< Is this call safe..........

lea eax,MyStruct ; <<<<<<<<<< as long as I do this before carrying on?

; carry on

assume eax:nothing

Is this safe?

Best regards,
Robin.

Yes that looks fine, you could PUSH EAX; POP EAX too. Or not save/restore it at all if the API/SUB doesn't change the value of EAX.

As noted previously ASSUME is an assemble time directive so MASM knows what you mean when you don't spell things out explicitly. ie It infers which structure, code/data/extra segment, etc should be the default. I'm pretty sure it doesn't stop you using explicit references, to this or other structures if you want.

The ASSUME has absolutely no impact on the API being called, it is not setting a state/register in the CPU.

Registers are always thread safe, each thread has it's own set of registers (context), so is the stack (above esp). What gets you in trouble is multiple threads fighting over a memory location they all see in common, usually who wrote to it last, and when reading it back whose value is there.

-Clive

[Astro]

Great! Thanks!

Best regards,
Robin.