Important: Undecorated DLL import

Question

Hello, I have a problem since 7 days and asked in several boards. Nobody knew the answer. I have a DLL created with Delphi which exports STDCALL functions with undecorated names (Pascal-Style). I do not want to decorate the names and I do not want to dynamically link the DLL.

I have created a DEF file which looks like this:

LIBRARY   statmondll32
EXPORTS
getVersionNumberA@0=getVersionNumberA

Then I compiled it with lib.exe

lib.exe /def:statmondll32.def /out:statmondll32.lib

When I view the LIB in dumpbin, I notice that the name is not undecorated (neither my alias is accepted):

  Symbol name  : _getVersionNumberA@0
  Type         : code
  Name type    : no prefix
  Hint         : 0
  Name         : getVersionNumberA@0

The name type is "no prefix". But when I look at WinAPI-LIBs (which are also STDCALL _and_ undecorated), they have "undecorate" as "name type".

I have found a workaround with an hexeditor, but it is very nasty in my opinion: I search the last occurence of "_getVersionNumberA@0" and then I go left 2 bytes. I change the byte 0x08 ("no prefix") into 0x0C ("undecorate").

After this, the dumpbin looks like this:

  Symbol name  : _getVersionNumberA@0
  Type         : code
  Name type    : undecorate
  Hint         : 0
  Name         : getVersionNumberA

My important question is, how can I tell lib.exe to undecorate the function names without using a hex-editor?

My product is MS VC++ 2010 Ultimate (student edition MSDNAA), Lib.exe version 10.00.30319.01.

Answer 1

Take a look at the section named Standard Call or PASCAL Functions in Creating Dynamic Link Libraries (non-Microsoft site); it has an interesting idea, which is to repeat the symbol thus:

LIBRARY   statmondll32
EXPORTS
getVersionNumberA@0
getVersionNumberA=getVersionNumberA@0

I'm not sure it will work, but it's worth a try IMO.

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Answering policy: see profile.

Answer 2

Thank you for your comment.

Alas, it does not work. It will create 2 different symbols which are both not working

Symbol #1:

  Symbol name  : _getVersionNumberA
  Type         : code
  Name type    : no prefix
  Hint         : 0
  Name         : getVersionNumberA

--> "Symbol name" is wrong. "Name" is ok.

Symbol #2:

  Symbol name  : _getVersionNumberA@0
  Type         : code
  Name type    : no prefix
  Hint         : 1
  Name         : getVersionNumberA@0

--> "Name" is wrong. "Symbol name" is ok.

Thus, C++ finds symbol #2 and tries to access "getVersionNumberA@0" in the DLL, which does not exist.

The information on that website related to "dlltool" with the "-k" (--kill-at) option. I am not sure where to find dlltool and if its LIB files are compatible with VC++ (I doubt it since e.g. Delphi's LIB files are also incompatible with VC++).

Answer 3

Can you show us how the functions are declared in the header your C++ application is importing in order to use the DLL?  I'm looking for the following aspects:

extern

extern "C"

stdcall

and of course the function declaration itself.

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Answer 4

I covered "undecorate" in my blog:

http://qualapps.blogspot.com/2007/08/how-to-create-32-bit-import-libraries.html

There's a lot of undocumented behavior that makes all of this work.

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Jim Beveridge