flat assembler - lstrlen, lstrlenA and lstrlenW

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Index > Windows > lstrlen, lstrlenA and lstrlenW - why ?

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IronFelix

Joined: 09 Dec 2004
Posts: 141
Location: Russia, Murmansk region

IronFelix 22 Apr 2009, 16:14

Hi all!
Please explain why there are "lstrlen" exported function along with "lstrlenA" and "lstrlenW" in kernel32.dll? Similar situation is in other dll's too. What is the difference between "lstrlen" and other functions in this case?

Thanks.

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22 Apr 2009, 16:14

asmcoder

Joined: 02 Jun 2008
Posts: 784

asmcoder 22 Apr 2009, 16:30

[content deleted]

Last edited by asmcoder on 14 Aug 2009, 14:51; edited 1 time in total

22 Apr 2009, 16:30

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19869
Location: In your JS exploiting you and your system

revolution 22 Apr 2009, 16:37

A and W versions are for ASCII (A) and UNICODE (W) versions. lstrlen is not a real import, it is aliased (by macros) to either the A or W version.

22 Apr 2009, 16:37

asmfan

Joined: 11 Aug 2006
Posts: 392
Location: Russian

asmfan 22 Apr 2009, 18:46

revolution actually it is real, but it has the same address as A version as other postfixless) APIs bound to A analogs.

22 Apr 2009, 18:46

IronFelix

Joined: 09 Dec 2004
Posts: 141
Location: Russia, Murmansk region

IronFelix 22 Apr 2009, 20:00

Thank you. So, as i supposed, it is better to use A and W versions and ignore such bounded/aliases exports?

22 Apr 2009, 20:00

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19869
Location: In your JS exploiting you and your system

revolution 23 Apr 2009, 01:12

asmfan wrote:

revolution actually it is real, but it has the same address as A version as other postfixless) APIs bound to A analogs.

It is only at the same address as the A version if you include win32ax. If you include win32wx then it is the same address as the W version. The macros are used to select which of the two will be imported. Have a look at the generated exe file with a hex editor you will see the appended A or W in the imports list.

23 Apr 2009, 01:12

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 23 Apr 2009, 01:28

revolution, lstrlen exists on KERNEL32.DLL. However, this is not true with every API of course, this is just one of the exceptional cases

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23 Apr 2009, 01:28

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19869
Location: In your JS exploiting you and your system

revolution 23 Apr 2009, 01:34

Oh, you are all talking about exports, I was talking about imports. Sorry for the confusion.

23 Apr 2009, 01:34

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