AccessViolation when calling C ++ - DLL from C ++ / CLI

Question

I wrote a C ++ / CLI wrapper for C ++ - DLLs to use this DLL in a C # program.

However, when I call a function that accepts char *, I get AccessViolation

int Wrapper::Net_methodX(int a, String^ key, long v)
{
    IntPtr ptr = Marshal::StringToHGlobalAnsi(key);
    pin_ptr<char> cKey = static_cast<char*>(ptr.ToPointer());
    int val = methodX(a,cKey, v); // AccessViolation here

    Marshal::FreeHGlobal(ptr);
    return val;
}

C ++ Signature - Functions

int methodX(int a, char *Key, long v);

EDIT 1

Just to “output”, like the following, it didn’t work:

int Wrapper::Net_methodX(int a, String^ key, long v)
{
    IntPtr ptr = Marshal::StringToHGlobalAnsi(key);
    char* cKey = static_cast<char*>(ptr.ToPointer());
    pin_ptr<char> pinned = cKey;
    int val = methodX(a,cKey, v);

    Marshal::FreeHGlobal(ptr);
    return val;
}

EDIT 1 END

EDIT 2

I also tried PtrToStringChars as follows (thanks Matt, I also found some document here ):

int Wrapper::Net_methodX(int a, String^ key, long v)
{
    pin_ptr<const wchar_t> wkey = PtrToStringChars(key);

    size_t convertedChars = 0;
    size_t  sizeInBytes = ((key->Length + 1) * 2);
    errno_t err = 0;
    char * ckey = (char * ) malloc(sizeInBytes);

    err = wcstombs_s(&convertedChars, ckey, sizeInBytes, wkey, sizeInBytes);

    int val = methodX(A_Symbol_Table,ckey, Value);

    return val;
}

AccessViolation still exists, maybe this is an error in the X () method (which is a third-party DLL).

EDIT 2 END

I read some related questions here, but have not yet found a solution.

Any clues? Thank.

Answer 1

, , . :

using namespace System;
using namespace System::Runtime::InteropServices;

ref class Wrapper
{
public:
    static int Net_methodX(int a, String^ key, long v);
};

int methodX(int a, char * pKey, long v)
{
    IntPtr ptr = static_cast<IntPtr>(pKey);
    String ^ pString = Marshal::PtrToStringAnsi(ptr);
    System::Console::WriteLine(pString);
    return a;
}

int Wrapper::Net_methodX(int a, String^ pKey, long v)
{     
    IntPtr ptr = Marshal::StringToHGlobalAnsi(pKey);     
    pin_ptr<char> cKey = static_cast<char*>(ptr.ToPointer());     
    int val = methodX(a,cKey, v); // AccessViolation here      
    Marshal::FreeHGlobal(ptr);     
    return val; 
}

void main()
{
    Wrapper wrapper;
    String ^ p = gcnew String("Hello");
    wrapper.Net_methodX(0, p, 0);
}

, :

• : http://support.microsoft.com/kb/311259
• pin_ptr . StringToHGlobalAnsi , , pin_ptr . Pin_ptr , , (, PtrToStringChars). , , , PtrToStringChars, .
• methodX, ? , .

Answer 2

, , , , , .

• sprintf : sprintf(cStr, "%s", clrString);. . .
• KB311259, . VS 2008 , marshal_as<> ( №4 ). , .

Answer 3

,

pin_ptr<char> cKey = static_cast<char*>(ptr.ToPointer());

, http://social.msdn.microsoft.com/forums/en-US/vclanguage/thread/0bd049fe-844a-4cb6-b9f6-c8f5107bc957

, .

Sujay