C ++无法识别DLL中的命令

Question

I am trying to make this DLL functionable but can't get it to work even from a ready code.

I create a simple DLL from visual studio in c++ (win32 project) and I have this 2 files that I use.

headerZincSDK.h

// headerZincSDK.h
#pragma once

#include <string>
#include <vector>

#if defined( WIN32 )
#include <tchar.h>
#define mdmT( x )   _T( x )
#else
#define mdmT( x )   L ## x
#endif

extern void OnEntry();

extern bool RegisterModule( const std::wstring& strName );

typedef struct
{
    int formId;
} 
ZincCallInfo_t;

typedef std::wstring ( *ZINC_COMMAND_CALLBACK )( const ZincCallInfo_t& info, const std::vector< std::wstring >& );

extern bool RegisterCommand( const std::wstring& strModuleName,
                     const std::wstring& strCommandName,
                     ZINC_COMMAND_CALLBACK callback );

// Helper commands for returning values
std::wstring AsString( const std::wstring& str );
std::wstring AsInteger( int value );
std::wstring AsBoolean( bool value );

And the Main Project.cpp

// Project1.cpp
#include "stdafx.h"

#include "headerZincSDK.h"

using namespace std;

BOOL APIENTRY DllMain( HMODULE hModule,
                       DWORD  ul_reason_for_call,
                       LPVOID lpReserved
                     )
{
    return TRUE;
}

void OnEntry()
 {
     wstring moduleName = mdmT( "TestExt" );

     RegisterModule( moduleName );

     RegisterCommand( moduleName, mdmT( "random" ), Command1 );

     RegisterCommand( moduleName, mdmT( "reverse" ), Command2 );
 } 

wstring Command1 (const ZincCallInfo_t& info, const vector< wstring >& vParams )
 {
     //My Code
 }

wstring Command2 (const ZincCallInfo_t& info, const vector< wstring >& vParams )
 {
     //My Code
 }

The problem is that it doesn't build the solution cause it says the Command1 and Command2 are undefined

I have none to nothing knowledge on c++ and these are my first steps but I can understand much and easy.

Can anyone tell me what shall I change in these to two files to make it work?

Answer 1

Functions Command1 and Command2 are not declared in header file with that typedef statement. That statement defines a type ZINC_COMMAND_CALLBACK , which is a pointer to a function whose signature matches that of functions Command1 and Command2 . This means that you can take the address of one of those functions (or any others function with the same signature) and assign it to this pointer:

ZINC_COMMAND_CALLBACK comm1 = &Command1;

The problem with your code is that you are using these functions before you have declared them. Either put entire definitions for Command1 and Command2 before function OnEntry , or leave definitions where they are and add the following declarations before OnEntry :

wstring Command1(const ZincCallInfo_t& info, const vector< wstring >& vParams);
wstring Command2(const ZincCallInfo_t& info, const vector< wstring >& vParams);

I have tested this code and it fixes errors related to Command1 and Command2 . New errors that appear are two linker errors caused by the fact that functions RegisterModule and RegisterCommand are not defined, but I am guessing that you omitted these definitions because they were not relevant to the question.

Answer 2

It worked but only with std infront of them

std::wstring Command1 (const ZincCallInfo_t& info, const vector< std::wstring >& vParams )
 {
     //My Code
 }

std::wstring Command2 (const ZincCallInfo_t& info, const vector< std::wstring >& vParams )
 {
     //My Code
 }

Otherwise it was full of errors dont know why. But i manage to enter this std:: infront and it works and yes before the onEntry() function

Thank you all for the quick responses