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Asked:2020-02-14 00:24:34 +0000 UTC2020-02-14 00:24:34 +0000 UTC

在 .dll (c#) 中找不到函数

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在我包含的 .dll 中找不到函数（funcPtr == 0）。我假设函数的名称在内部以某种方式被编码或更改，但我自己还无法弄清楚。

程序：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using System.Windows;

namespace Lab1Dynamic
{
    class Program
    {
        [DllImport("kernel32", SetLastError = true, CharSet = CharSet.Ansi)]
        static extern IntPtr LoadLibrary([MarshalAs(UnmanagedType.LPStr)]string lpFileName);

        [DllImport("kernel32", CharSet = CharSet.Ansi, ExactSpelling = true, SetLastError = true)]
        static extern IntPtr GetProcAddress(IntPtr hModule, string procName);

        [DllImport("kernel32", SetLastError = true, EntryPoint = "GetProcAddress")]
        static extern IntPtr GetProcAddressOrdinal(IntPtr hModule, IntPtr procName);

        private delegate double fDelegate(double x, double y);
        static void Main(string[] args)
        {
            var dllPath = "MyLibrary.dll";
            IntPtr dllInstance = LoadLibrary(dllPath);
            while (dllInstance == IntPtr.Zero)
            {    
                Console.ForegroundColor = ConsoleColor.Red;
                Console.WriteLine("Can't load DLL " + dllPath);

                Console.ForegroundColor = ConsoleColor.Gray;
                Console.WriteLine("Write the path below...");
                dllPath = Console.ReadLine();
                dllInstance = LoadLibrary(dllPath);
            }

            string fname = "f";
            IntPtr funcPtr = GetProcAddress(dllInstance, fname);
            fDelegate fd = (fDelegate)Marshal.GetDelegateForFunctionPointer(funcPtr,
                typeof(fDelegate));
            var y = fd(1.0, 2.0);
        }
    }
}

dll：

using System;

namespace MyProj
{
    public class MyLibrary
    {
        public static double f(double x, double y) => 3 * Math.Sin(x) + 2 * Math.Cos(y);
    }
}

DLL（C++，VS2019）：MyLib.h：

#pragma once
extern "C" __declspec(dllexport) double f(const double x, const double y);

MyLib.cpp：

#include "MyLib.h"
#include "pch.h"
#include <cmath>
double f(const double x, const double y)
{
    return 3 * sin(x) + 2 * cos(y);
}

PS根据MDSN的指南here

c#

1 个回答

  1. Best Answer

    您应该注意的第一件事是您的项目中使用了哪种约定：

    在此处输入图像描述

    接下来，在形成非托管导入函数的委托时，您需要添加适当的属性：

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
private delegate double ImportFDelegate(double x, double y);

    接下来，在请求指向非托管函数的指针时，请确保传递正确的函数名称：

    就我而言：

    C:\Users\ヒミコ\source\repos\SO\Debug>dumpbin /exports MyLib.dll
Microsoft (R) COFF/PE Dumper Version 14.24.28316.0
Copyright (C) Microsoft Corporation.  All rights reserved.


Dump of file MyLib.dll

File Type: DLL

  Section contains the following exports for MyLib.dll

    00000000 characteristics
    FFFFFFFF time date stamp
        0.00 version
           1 ordinal base
           1 number of functions
           1 number of names

    ordinal hint RVA      name

          1    0 0001117C f = @ILT+375(_f) // Здесь указано экспортированное имя, и реальное, реальное с подчеркиванием
                                           // подробнее на MSDN https://docs.microsoft.com/ru-ru/cpp/cpp/argument-passing-and-naming-conventions?view=vs-2019

  Summary

        1000 .00cfg
        1000 .data
        1000 .idata
        1000 .msvcjmc
        2000 .rdata
        1000 .reloc
        1000 .rsrc
        6000 .text
       10000 .textbss

C:\Users\ヒミコ\source\repos\SO\Debug>

    还要确保项目的位深度匹配，即 如果库是 x86，那么项目在 c# x86 中，与 x64 相同。

    以下是更正后的代码：

    class Program
{
    [DllImport("kernel32", SetLastError = true, CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Winapi)]
    static extern IntPtr LoadLibrary(string lpFileName);

    [DllImport("kernel32", CharSet = CharSet.Ansi, SetLastError = true, CallingConvention = CallingConvention.Winapi)]
    static extern IntPtr GetProcAddress(IntPtr hModule, string procName);

    [DllImport("kernel32", SetLastError = true, CallingConvention = CallingConvention.Winapi)]
    [return: MarshalAs(UnmanagedType.Bool)]
    static extern bool FreeLibrary(IntPtr moduleHandle);

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    private delegate double ImportFDelegate(double x, double y);

    static void Main(string[] args)
    {
        string dllPath = "MyLibrary.dll";
        IntPtr dllInstance = LoadLibrary(dllPath);

        while (dllInstance == IntPtr.Zero)
        {
            int errorCode = Marshal.GetLastWin32Error();
            Win32Exception exception = new Win32Exception(errorCode);
            Console.ForegroundColor = ConsoleColor.Red;
            Console.WriteLine("Unable to load library {1}:\n\t{0}", exception.Message, Path.GetFileName(dllPath));

            Console.ResetColor();
            Console.WriteLine("Write the path below...");
            dllPath = Console.ReadLine();
            dllInstance = LoadLibrary(dllPath);
        }

        const string functionName = "f";
        IntPtr funcPtr = GetProcAddress(dllInstance, functionName);

        if (funcPtr == IntPtr.Zero)
        {
            int errorCode = Marshal.GetLastWin32Error();
            Win32Exception exception = new Win32Exception(errorCode);
            Console.ForegroundColor = ConsoleColor.Red;
            Console.WriteLine("Unable to get address of function: {0}\n\t{1}", functionName, exception.Message);
            return;
        }

        ImportFDelegate fd = (ImportFDelegate)Marshal.GetDelegateForFunctionPointer(funcPtr, typeof(ImportFDelegate));
        double result = fd(1.0, 2.0);

        Console.WriteLine("Imported function return result: {0:N}", result);

        FreeLibrary(dllInstance);
    }
}

    这是程序的实际输出：

    Unable to load library MyLibrary.dll:
        Не найден указанный модуль
Write the path below...
MyLib.dll
Imported function return result: 1,69
    • 2

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