.net - 为什么我的多线程 C++ .NET 应用程序只有在 visual studio 之外执行时才会崩溃？

Question

我使用托管和非托管代码创建了一个非常简单的 C++ .NET 应用程序来重现我的问题。

当用户单击一个按钮时，应该会产生一个新线程并执行一些耗时的任务，同时使用状态更新回调我的主线程。

此代码在 Visual Studios Express 2010 内部编译并成功执行。也就是说，当我单击“播放”按钮时，我的项目会构建并执行而不会崩溃。但是，如果我转到可执行文件所在的 Release 文件夹并运行它，则单击该按钮后应用程序就会崩溃。我正在使用/clr 并在 Release模式下进行编译。

我创建了一个表单并添加了一个按钮。 Form1.h 的代码如下所示:

#pragma once

#include "core.h"
#include <Windows.h>
#include <process.h>

namespace RepErr {

    using namespace System;
    using namespace System::ComponentModel;
    using namespace System::Collections;
    using namespace System::Windows::Forms;
    using namespace System::Data;
    using namespace System::Drawing;

    using namespace System::Runtime::InteropServices;

    int x;

    /// <summary>
    /// Summary for Form1
    /// </summary>
    public ref class Form1 : public System::Windows::Forms::Form
    {
    public:
        Form1(void)
        {
            InitializeComponent();
            //
            //TODO: Add the constructor code here
            //
        }

    protected:
        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        ~Form1()
        {
            if (components)
            {
                delete components;
            }
        }
    private: System::Windows::Forms::Button^  button1;

    protected: 

    private:
        /// <summary>
        /// Required designer variable.
        /// </summary>
        System::ComponentModel::Container ^components;

#pragma region Windows Form Designer generated code
        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        void InitializeComponent(void)
        {
            this->button1 = (gcnew System::Windows::Forms::Button());
            this->SuspendLayout();
            // 
            // button1
            // 
            this->button1->Location = System::Drawing::Point(104, 62);
            this->button1->Name = L"button1";
            this->button1->Size = System::Drawing::Size(75, 23);
            this->button1->TabIndex = 0;
            this->button1->Text = L"button1";
            this->button1->UseVisualStyleBackColor = true;
            this->button1->Click += gcnew System::EventHandler(this, &Form1::button1_Click);
            // 
            // Form1
            // 
            this->AutoScaleDimensions = System::Drawing::SizeF(6, 13);
            this->AutoScaleMode = System::Windows::Forms::AutoScaleMode::Font;
            this->ClientSize = System::Drawing::Size(276, 160);
            this->Controls->Add(this->button1);
            this->Name = L"Form1";
            this->Text = L"Form1";
            this->ResumeLayout(false);

        }
#pragma endregion
    private: System::Void button1_Click(System::Object^  sender, System::EventArgs^  e) {
                 core *o1 = new core();
                 unsigned  uiThread1ID;
                 HANDLE hth1 = (HANDLE)_beginthreadex(NULL, 0, core::ThreadStaticEntryPoint, o1, CREATE_SUSPENDED, &uiThread1ID);
                 ResumeThread( hth1 );
             }

public:

    static void* callback(int smallIndex) {
        x = smallIndex;
        void* dtpage = NULL;
        return dtpage;
    }

    delegate void* myCALLBACKDelegate(int smallIndex);

    static GCHandle gch;

    //static constructor, initialize delegate here
    static Form1() {
        myCALLBACKDelegate^ fp=gcnew myCALLBACKDelegate(callback);
        gch = GCHandle::Alloc(fp);
        formCallback = static_cast<myCALLBACK>(Marshal::GetFunctionPointerForDelegate(fp).ToPointer());
    }

};
}

这是 core.h 的代码:

`#pragma once

#include <vcclr.h>
#include "Form1.h"

extern "C" { 
    typedef void* (__stdcall *myCALLBACK)(int smallIndex);
}

// static pointer to managed function
myCALLBACK formCallback;

public class core {
public:

    core() {}

    static unsigned __stdcall ThreadStaticEntryPoint(void *pThis) {
        core *pCr = (core*)pThis;
        pCr->doCall();
        return 1;
    }

    void doCall() {
        formCallback(1);
    }

};

#pragma endregion

为什么此应用程序会在 Visual Studio 之外崩溃？我是否需要将某些 dll 或 .NET 文件与可执行文件放在同一目录中？

谢谢， 威廉

如果我将警告级别更改为最高详细级别，编译器输出:

1>c:\users\bill\documents\visual studio 2010\projects\reperr\reperr\Form1.h(107): warning C4434: a static constructor must have private accessibility; changing to private access
1>c:\users\bill\documents\visual studio 2010\projects\reperr\reperr\Form1.h(87): warning C4100: 'e' : unreferenced formal parameter
1>c:\users\bill\documents\visual studio 2010\projects\reperr\reperr\Form1.h(87): warning C4100: 'sender' : unreferenced formal parameter
1>RepErr.cpp(9): warning C4100: 'args' : unreferenced formal parameter
1>RepErr.cpp(19): warning C4339: '_TP_POOL' : use of undefined type detected in CLR meta-data - use of this type may lead to a runtime exception
1>RepErr.cpp(19): warning C4339: '_TP_CLEANUP_GROUP' : use of undefined type detected in CLR meta-data - use of this type may lead to a runtime exception
1>RepErr.cpp(19): warning C4339: '_TP_CALLBACK_INSTANCE' : use of undefined type detected in CLR meta-data - use of this type may lead to a runtime exception
1>RepErr.cpp(19): warning C4339: '_ACTIVATION_CONTEXT' : use of undefined type detected in CLR meta-data - use of this type may lead to a runtime exception
1>  Generating Code...
1>c:\Users\Bill\documents\visual studio 2010\Projects\RepErr\RepErr\RepErr.cpp : warning C4710: '__clrcall RepErr::Form1::~Form1(void)' : function not inlined
1>c:\users\bill\documents\visual studio 2010\projects\reperr\reperr\form1.h(28): warning C4710: 'void __clrcall RepErr::Form1::InitializeComponent(void)' : function not inlined
1>c:\users\bill\documents\visual studio 2010\projects\reperr\reperr\reperr.cpp(16): warning C4710: '__clrcall RepErr::Form1::Form1(void)' : function not inlined
1>  .NETFramework,Version=v4.0.AssemblyAttributes.cpp
1>  RepErr.vcxproj -> c:\users\bill\documents\visual studio 2010\Projects\RepErr\Release\RepErr.exe
========== Build: 1 succeeded, 0 failed, 0 up-to-date, 0 skipped ==========

这是 RepErr.cpp:

// RepErr.cpp : main project file.

#include "stdafx.h"
#include "Form1.h"

using namespace RepErr;

[STAThreadAttribute]
int main(array<System::String ^> ^args)
{
    // Enabling Windows XP visual effects before any controls are created
    Application::EnableVisualStyles();
    Application::SetCompatibleTextRenderingDefault(false); 

    // Create the main window and run it
    Application::Run(gcnew Form1());
    return 0;
}

Answer 1

程序正在崩溃，因为 formCallback 为 NULL(因此 core::doCall 取消引用 NULL 指针)。 formCallback 为 NULL，因为初始化它的 Form1 静态构造函数永远不会运行。

您可以通过将以下行添加到 Form1 静态构造函数来演示这一点:

static Form1() {
    // ... other initialisation ...
    MessageBox::Show(((int) formCallback).ToString("x8"));
}

在调试构建(或在 VS 调试器下运行的发布)中，将显示一个带有函数指针值的消息框。在发布版本中(不在调试器下)，此对话框不会显示，因为静态构造函数未运行。

静态构造函数未运行，因为类型标记为 BeforeFieldInit .这意味着“类型的初始化方法在第一次访问为该类型定义的任何静态字段时或之前的某个时间执行”。如果没有任何静态字段的访问权限，则不需要运行静态构造函数(在发布版本中，它不需要)。

根据 this Connect issue ，这是设计使然。解决方法是在实例 Form1 构造函数中访问您类型的静态字段，这将强制静态构造函数运行，这将正确初始化 formCallback:

static int s_dummy;

public:
    Form1()
    {
        // force static constructor to run now
        s_dummy = 0;

        InitializeComponent();
    }

或者(也是我推荐的)，使用 Thread类创建一个新的托管线程；这将避免对托管委托(delegate)、GCHandle、formCallback 全局函数指针和静态构造函数的需要。如果您需要执行非托管代码，您可以从该托管线程调用 native C++。