sizeof Invoke, Call structures ?

[K_F]

Search is getting me nowhere fast... :)
Does anybody have an idea of the assembler output code size of Invoke or Call instructions..
I would like to make a jump to call table and need to know alignment sizes.

I'll carry on looking at some pdf's but .. ja!
Thanks

[hamper]

I don't know whether this helps or not (new to assembler) and it may not be what you are looking for, but...

Don't know about invoke, but according to the Intel reference manual, call is a single opcode either E8, FF or 9A depending on how the call is made.

[jj2007]

Code size depends
a) on the type and number of args pushed (or passed via FastCall in ecx etc)
b) whether you call a global variable (invoke MyTest, ....) or if you use call edx, call [edx], call [edx+eax+120] etc

[dedndave]

well - API's are invoked with a jmp to a table - 5 bytes
1 byte opcode - 4 byte address
i seem to remember they use "2-aligned" branches in the IAT   :lol:
one every 6 bytes

[Tedd]

5 bytes for the call, so align it to 6 minimally, or 8 if you're feeling generous. Debug an exe to see how it's usually done.

Depending how flexible you can be, a table of offsets might be preferable - then you can either load the offset into a reg and call reg (though you'll require an extra ret to get back to the original caller), or copy the offset into a known location for which the next instruction instruction does an indirect jmp.

[dedndave]

yes - a table of offsets...
i use them rather often as Branch Vector Tables
but - that is when you have an index in a register or something

nice thing is - they can stay 4-aligned without wasting space

this is related to the thread of Jochen's   :P

... or copy the offset into a known location for which the next instruction does an indirect jmp.

that can be both variable and invoked   :t

[K_F]

Thanks..
I've used offset jump tables in other Asm's... my brain just went mushy with as I'd never done it before with Masm.

So essentially we're talking about Offsets being better, something like COM vector tables.
:t

[dedndave]

yes - i am reminded of the original x86 interrupt vector tables, but they were FAR's