push ecx+1 trashes ebx?

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Azu

Joined: 16 Dec 2008
Posts: 1159

Azu 29 Apr 2009, 21:17

"push ecx+1" is trashing ebx, why?? Is there a way to make it trash something else instead?

Edit: actually I'm not sure WHAT it's trashing.

It crashes my program even if I preserve every single register;

Code:

pushad
push    ecx+1
add    esp,4
popad

Why??

P.S. if I remove the +1 it is fine.

29 Apr 2009, 21:17

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 29 Apr 2009, 21:38

Code:

00401001   60               PUSHAD
00401002   51               PUSH ECX
00401003   6A 01            PUSH 1
00401005   83C4 04          ADD ESP,4
00401008   61               POPAD

"push ECX+1" is not the equivalent of push ecx/lea ecx,[ecx+1]/xchg ecx, [esp] but push ecx/push +1 instead.

push and pop supports an arbitrary number of operands without comma separation

29 Apr 2009, 21:38

Azu

Joined: 16 Dec 2008
Posts: 1159

Azu 29 Apr 2009, 21:44

Thanks ^^ that explains a lot.

29 Apr 2009, 21:44

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