MSVC C++ Name Mangling From String On Runtime

Question

First i will start with the reason i need name mangling on runtime.

I need to create a bridge between dll and its wrapper

namespace Wrapper
{
    class  __declspec(dllexport) Token
    {
    public:

        virtual void release() {}
    };
}

class  __declspec(dllexport) Token
{
public:

    virtual void release(){}
};

The idea is to use dumpin to generate all the mangled names of the dll holding class token and than demangled them.

?release@Token@@UAEXXZ --> void Token::release(void)

after that i want to convert is to match the Wrapper so i will need to change the function name

void Token::release(void) --> void Wrapper::Token::release(void)

and then i need to mangle it again so i can create a def file that direct the old function to the new one.

?release@Token@@UAEXXZ = ?release@Token@Wrapper@@UAEXXZ

all this process needs to be on run time.

First and the easiest solution is to find a function that mangle strings but i couldn't find any...

any other solution?

Looks a bit solution oriented. Please read [this](https://meta.stackexchange.com/questions/66377/what-is-the-xy-problem). — StoryTeller - Unslander Monica, Mar 14 '19 at 09:54

Botje · Accepted Answer · 2019-03-17T10:47:54.123

2

The Clang compiler is ABI-compatible with MSVC, including name mangling. The underlying infrastructure is part of the LLVM project, and I found llvm-undname which demangles MSVC names. Perhaps you can rework it to add the Wrapper:: namespace to symbols and re-mangle.

You can find inspiration about mangling names in this test code.

edited Mar 17 '19 at 10:47

answered Mar 14 '19 at 10:02

Botje

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windows have already UnDecorateSymbolName that demangle function from string.. what is need is DecorateSymbolName.. dose the llvm have mangle function? – lior Mar 14 '19 at 10:11
Yes, as that is how it generates symbol names. See [this test code](https://github.com/llvm-mirror/llvm/blob/master/unittests/IR/ManglerTest.cpp#L67) for example. – Botje Mar 14 '19 at 10:23

EmDroid · Answer 2 · 2019-03-14T10:26:30.250

If you are allowed to change the DLL, I'd usually use a different approach, by exporting extern "C" getter function (that does not mangle thus doesn't need demangling) and using virtual interface to access the class (note that the virtual interface doesn't need to be dllexported then). Your Token interface seems to be virtual anyway.

Something along those lines (not tested, just to show the idea):

DLL access header:

class Token  // notice no dllexport!
{
protected:
    // should not be used to delete directly (DLL vs EXE heap issues)
    virtual ~Token() {}
    virtual void destroyImpl() = 0; // pure virtual
public:
    static inline void destroy(Token* token) {
        // need to check for NULL otherwise virtual call would segfault
        if (token) token->destroyImpl();
    }
    virtual void doSomething() = 0; // pure virtual
};

extern "C" __declspec(dllexport) Token * createToken();

DLL implementation:

class TokenImpl: public Token
{
public:
    virtual void destroyImpl() {
        delete this;
    }
    virtual void doSomething() {
        // implement here
    }
};

extern "C" __declspec(dllexport) Token * createToken()
{
    return new TokenImpl;
}

Usage:

// ideally wrap in RAII to be sure to always release
// (e.g. can use std::shared_ptr with custom deleter)
Token * token = createToken();

// use the token
token->doSomething();

// destroy
Token::destroy(token);

With shared::ptr (can also create a typedef/static inline convenience creator function in the Token interface):

std::shared_ptr<Token> token(createToken(),
                             // Use the custom destroy function
                             &Token::destroy);
token->doSomething()
// token->destroy() called automatically when last shared ptr reference removed

This way you only need to export the extern-C creator function (and the release function, if not part of the interface), which will then not be mangled thus easy to use via the runtime loading.

MSVC C++ Name Mangling From String On Runtime

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