sub rsp,16 vs sub esp,16

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mattst88

Joined: 12 May 2006
Posts: 260
Location: South Carolina

mattst88 16 May 2007, 01:23

When allocating space on the stack, is it safe to use sub esp,16? Is there a chance for over/underflow?

The benefit is that it is one byte smaller.

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16 May 2007, 01:23

Feryno

Joined: 23 Mar 2005
Posts: 514
Location: Czech republic, Slovak republic

Feryno 16 May 2007, 08:07

Hello mattst88
on my Fedora Core 3 x64 and kernel 2.6.xx.xx (I can't remember exactly the number now) the stack is usally above 100000000h (I think it is something like 00007FFFFFFFFxxxh) so every subtraction from ESP causes destroying the upper dword of rsp and losing the stack pointer completely.
Perhaps in your Linux it doesn't matter, but my personal suggestion is to use RSP for keeping compactibility between various kernels and configurations.

16 May 2007, 08:07

mattst88

Joined: 12 May 2006
Posts: 260
Location: South Carolina

mattst88 16 May 2007, 13:28

OK, I'll stick with rsp. Smile

Thanks for your reply.

16 May 2007, 13:28

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