Using LocalFree

flat assembler
Message board for the users of flat assembler.

Index > Windows > Using LocalFree

Author

Thread

ctl3d32

Joined: 30 Dec 2009
Posts: 206
Location: Brazil

ctl3d32 04 Sep 2010, 22:44

Hi folks!

I need a little help to delete a local <QWORD> variable from memory. LocalFree does not work in the code below. How can i do that?

ex.:

Code:

proc sGetElem M,ir,ic

     local nr:QWORD
     invoke  LocalFree,[nr]
     ret
endp

Thanks for reading,
ctl3d32

04 Sep 2010, 22:44

Tyler

Joined: 19 Nov 2009
Posts: 1216
Location: NC, USA

Tyler 04 Sep 2010, 23:57

Locals are declared on the stack, are deleted after endp... assuming it gets to endp, remove that ret.

04 Sep 2010, 23:57

windwakr

Joined: 30 Jun 2004
Posts: 827

windwakr 05 Sep 2010, 00:05

Tyler wrote:

Locals are declared on the stack, it is deleted after endp... assuming it gets to endp, remove that ret.

The ret is needed.

For example, lets say I have this pointless proc:

Code:

proc a a,b,c
local nr:QWORD
mov eax,1
endp

It becomes:

Code:

push ebp
mov ebp,esp
sub esp,8
mov eax,1

With a ret after the "mov eax,1" line:

Code:

push ebp
mov ebp,esp
sub esp,8
mov eax,1
leave
retn 0xC

_________________
----> * <---- My star, won HERE

05 Sep 2010, 00:05

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20445
Location: In your JS exploiting you and your system

revolution 05 Sep 2010, 00:17

You don't need to free anything. Just use:

Code:

proc sGetElem M,ir,ic

     local nr:QWORD
;...
     ret
endp

The ret will tidy up the stack properly.

05 Sep 2010, 00:17

ctl3d32

Joined: 30 Dec 2009
Posts: 206
Location: Brazil

ctl3d32 05 Sep 2010, 00:47

Hi!

Good to know i don't have to free them by myself.

Thank you all for the quick reply!

05 Sep 2010, 00:47

Tyler

Joined: 19 Nov 2009
Posts: 1216
Location: NC, USA

Tyler 05 Sep 2010, 00:49

Wow, I didn't know that(obviously). I've never used procs for the very reason that I thought it was impossible to have multiple returns

05 Sep 2010, 00:49

< Last Thread | Next Thread >

Forum Rules:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum