Unmangling C++ DLL Function Names

Question

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How do I stop name-mangling of my DLL's exported function?

I have a DLL that is written in C++. The exported function names need to be unmangled. For example, int MyFunc( int Param1, int Param2 ); needs to appear to an outside application trying to call the library function simply as MyFunc. However, when I look at it using Dependency Walker, it looks like _MyFunc@8. This is how I have it declared in C++:

extern "C" __declspec(dllexport) int WINAPI MyFunc( int Param1, int Param2 );

I thought the extern "C" would do the trick. How do I get rid of the mangling? Thanks.

duplicate? http://stackoverflow.com/questions/1467144/how-do-i-stop-name-mangling-of-my-dlls-exported-function — MerickOWA, Jan 25 '11 at 15:15
also useful link - http://msdn.microsoft.com/en-US/library/x7kb4e2f(v=VS.80).aspx — MerickOWA, Jan 25 '11 at 15:17
@ThomasMcLeod: The `WINAPI` macro is in my code. I forgot to add it in the the sample code that I posted. It is there now. — Jim Fell, Jan 25 '11 at 15:33

Chris Becke · Accepted Answer · 2011-01-25T15:31:06.753

8

Ways to get rid of mangling: (assuming MSVC is the build environment)

Export via a .DEF file.

Export as extern "C" ensuring that the __cdecl calling convention is used. __stdcall prepends the _ and postpends the @ on dll exported functions even when extern "C" is used.

extern "C" __declspec(dllexport) int __cdecl MyFunc(int Param1, int Param2);

Export using a #pragma directive. You need to pass the fully mangled name on the other side of this. __FUNCDNAME__ is a useful directive to put in a macro in a function to list its decorated name,

#pragma comment(linker, "/EXPORT:MyFunc=_MyFunc@8");

edited Jan 25 '11 at 15:31

answered Jan 25 '11 at 15:18

Chris Becke

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Does `extern "C"` ensure that the `__cdecl` calling convention is used, or are those two separate things? – Jim Fell Jan 25 '11 at 15:30
extern "C" merely ensures that the symbol is compatible with C code. __cdecl and __stdcall are separate directives that can be applied to fully decorated c++ functions – Chris Becke Jan 25 '11 at 15:32
1

Should the pragma go immediately before the function declaration? – Jim Fell Jan 25 '11 at 15:35
The pragma solution did the trick. Not the cleanest way to do it, as it leaves the mangled artifacts in the DLL. However, for my particular situation this is simple and effective. – Jim Fell Jan 25 '11 at 15:45

score 3 · Answer 2 · answered Jan 25 '11 at 15:25

3

The leading underscore and @8 suffix are not from C++ name mangling, but rather denote stdcall calling convention, as is normal for dllexport.

answered Jan 25 '11 at 15:25

Simon Richter

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Okay. How do I get rid of them? – Jim Fell Jan 25 '11 at 15:26
You change your calling convention to one that does not do such mangling. – Jonathan Grynspan Jan 25 '11 at 15:34
1

If you use *cdecl* calling convention, these will go away, however your application needs to be aware of that. – Simon Richter Jan 25 '11 at 15:35
Unfortunately, the `WINAPI` macro (which translates to `__stdcall`) is required to maintain compatibility with other applications that are already deployed. – Jim Fell Jan 25 '11 at 15:38
1

This sounds to me like the new application is unaware that this is a *stdcall* function, otherwise it'd refer to the decorated name (or are you resolving the name explicitly?). – Simon Richter Jan 25 '11 at 15:56

score 2 · Answer 3 · answered Jan 25 '11 at 15:17

2

This is probably because you did not put extern "C" declspec on the function definition, you only put it on the declaration.

answered Jan 25 '11 at 15:17

CharlesB

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It is on both the declaration and the definition. – Jim Fell Jan 25 '11 at 15:24

score 0 · Answer 4 · answered Jan 25 '11 at 15:19

0

On the header (.h), define it as:

extern "C" 
{
  __declspec(dllexport) int __stdcall MyFunc( int Param1, int Param2 );
}

Then, on the implementation (.cpp) of the function:

extern "C"
{
  __declspec(dllexport) int __stdcall MyFunc( int Param1, int Param2 )
  {
     // ... code ...
  }
}

answered Jan 25 '11 at 15:19

karlphillip

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It has to be done using brackets? Declaring `extern "C"` incline does not do the same thing? – Jim Fell Jan 25 '11 at 15:26
@Jim You are right, you don't need brackets. I just put it for the sake of completeness. – karlphillip Jan 25 '11 at 15:27

score 0 · Answer 5 · answered Jan 25 '11 at 18:35

0

On Gnu systems there is c++filt

answered Jan 25 '11 at 18:35

doron

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And on Windows it's `undname`. But the question's about stopping the mangling not decoding it. – Rup Jan 25 '11 at 18:37

Unmangling C++ DLL Function Names

5 Answers5