有没有更好的方法来加载dll在C ++？ [英] Is there a better way to load a dll in C++?

问题描述

现在我做这样的事情，如果我结束了很多功能，我想在我的DLL中引用，这似乎很乱。有没有更好更干净的访问功能的方法，而不必为每个函数定义创建一个typedef，以便它能够正确地编译和加载函数。我的意思是函数定义已经在.h文件中，我不必在加载函数后重新声明它们（或者是我吗？）有没有比使用LoadLibary更好的解决方案？我不一定需要这个功能，如果有办法可以在Visual Studio 2005项目设置中做同样的事情。

Right now I do something like this and it seems messy if I end having a lot of functions I want to reference in my DLL. Is there a better and cleaner way of accessing the functions without having to create a typedef for each function definition so that it will compile and load the function properly. I mean the function definitions are already in the .h file and I shouldn't have to redeclare them after I load the function (or do I?) Is there a better solution than using LoadLibary? I don't necessarily need that function if there is a way I can do the same thing within Visual Studio 2005 project settings.

#include "stdafx.h"
#include <windows.h>

#ifndef BHANNAN_TEST_CLASS_H_
#define BHANNAN_TEST_CLASS_H_

extern "C" {

    // Returns n! (the factorial of n).  For negative n, n! is defined to be 1.
    int __declspec (dllexport) Factorial(int n);

    // Returns true iff n is a prime number.
    bool __declspec (dllexport) IsPrime(int n);

}

#endif  // BHANNAN_TEST_CLASS_H_

---

BHannan_Test_Class.cpp

---

BHannan_Test_Class.cpp

#include "stdafx.h"
#include "BHannan_Test_Class.h"

// Returns n! (the factorial of n).  For negative n, n! is defined to be 1.
int Factorial(int n) {
  int result = 1;
  for (int i = 1; i <= n; i++) {
    result *= i;
  }

  return result;
}

// Returns true iff n is a prime number.
bool IsPrime(int n) {
  // Trivial case 1: small numbers
  if (n <= 1) return false;

  // Trivial case 2: even numbers
  if (n % 2 == 0) return n == 2;

  // Now, we have that n is odd and n >= 3.

  // Try to divide n by every odd number i, starting from 3
  for (int i = 3; ; i += 2) {
    // We only have to try i up to the squre root of n
    if (i > n/i) break;

    // Now, we have i <= n/i < n.
    // If n is divisible by i, n is not prime.
    if (n % i == 0) return false;
  }

  // n has no integer factor in the range (1, n), and thus is prime.
  return true;
}

---

dll_test.cpp < h2>

---

dll_test.cpp

#include <BHannan_Test_Class.h>

typedef int (*FactorialPtr) (int);
FactorialPtr myFactorial=NULL;

// Tests factorial of negative numbers.
TEST(FactorialTest, Negative) {

    HMODULE myDLL = LoadLibrary("BHannan_Sample_DLL.dll");

    if(myDLL) {
        myFactorial = (FactorialPtr) GetProcAddress(myDLL,"Factorial");

        if(myFactorial)
        {
            EXPECT_EQ(1, myFactorial(-5));
            EXPECT_EQ(1, myFactorial(-1));
            EXPECT_TRUE(myFactorial(-10) > 0);
        }

        FreeLibrary(myDLL);
    }

}

推荐答案

建立你的.dll后，可以在附近找到.lib文件并将你的测试应用程序与它连接起来。使用在.h中声明的功能

After building your .dll get the .lib file nearby and link your test application with it. Use functions as they are declared in .h

您的标题文件中需要做一些细微的更改：

There's a minor change you need to do in your header file:

#ifdef EXPORTS_API
  #define MY_API_EXPORT __declspec (dllexport)
#else
  #define MY_API_EXPORT __declspec (dllimport)
#endif

extern "C" {
    int MY_API_EXPORT Factorial(int n);

    // do the same for other functions
}

这样，在构建您的dll时，您可以在项目设置中定义 EXPORTS_API ，并在客户端应用程序中导出功能，无需定义任何内容。

This way, when building your dll you define EXPORTS_API in your project settings and functions get exported, in the client application, no need to define anything.

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