dotnet core 应用是如何跑起来的 通过自己写一个 dotnet host 理解运行过程

int wmain(int argc, wchar_t* argv[])
{
    printf("Sample CoreCLR Host\n\n");
    // 替换下面的代码
    wchar_t* application = L"c:\\lindexi\\Code\\HostWithMscoree\\dll\\ManagedLibrary.dll";
    const wchar_t* coreCLRDirectory = L"c:\\lindexi\\Code\\HostWithMscoree\\framework\\";

    // 忽略代码
}

int wmain(int argc, wchar_t* argv[])
{
    printf("Sample CoreCLR Host\n\n");
    // 替换下面的代码
    wchar_t* application = L"c:\\lindexi\\Code\\HostWithMscoree\\dll\\ManagedLibrary.dll";
    const wchar_t* coreCLRDirectory = L"c:\\lindexi\\Code\\HostWithMscoree\\framework\\";

    // 忽略代码
}

        const wchar_t* coreCLRDirectory = L"c:\\lindexi\\Code\\HostWithMscoree\\framework\\";

        // 下面代码相当于 string coreRoot = coreCLRDirectory; 而已
        wchar_t coreRoot[MAX_PATH];
        wcscpy_s(coreRoot, MAX_PATH, coreCLRDirectory);

        HMODULE coreCLRModule;
        coreCLRModule = LoadCoreCLR(coreRoot);

HMODULE LoadCoreCLR(const wchar_t* directoryPath)
{
    wchar_t coreDllPath[MAX_PATH];
    // 下面代码其实就是 coreDllPath = "c:\\lindexi\\Code\\HostWithMscoree\\framework\\" + "\\" + "coreclr.dll";
    wcscpy_s(coreDllPath, MAX_PATH, directoryPath);
    wcscat_s(coreDllPath, MAX_PATH, L"\\");
    wcscat_s(coreDllPath, MAX_PATH, coreCLRDll);

    // 以下是核心代码，通过 LoadLibraryExW 加载 CoreClr.dll 文件
    // <Snippet2>
    HMODULE ret = LoadLibraryExW(coreDllPath, NULL, 0);
    // </Snippet2>

    if (!ret)
    {
        // This logging is likely too verbose for many scenarios, but is useful
        // when getting started with the hosting APIs.
        DWORD errorCode = GetLastError();
        wprintf(L"CoreCLR not loaded from %s. LoadLibrary error code: %d\n", coreDllPath, errorCode);
    }

    return ret;
}

// 这是在 Windows 下的写法，在 Windows 下是加载 CoreClr.dll 文件
// Main clr library to load
// Note that on Linux and Mac platforms, this library will
// be called libcoreclr.so or libcoreclr.dylib, respectively
static const wchar_t* coreCLRDll = L"coreclr.dll";

    // 从 CoreClr.dll 里面获取 GetCLRRuntimeHost 方法
    // 相当于拿到 HRESULT GetCLRRuntimeHost(Guid id, out ICLRRuntimeHost4 runtimeHost); 方法
    FnGetCLRRuntimeHost pfnGetCLRRuntimeHost =
        (FnGetCLRRuntimeHost)::GetProcAddress(coreCLRModule, "GetCLRRuntimeHost");

    // 通过 pfnGetCLRRuntimeHost 拿到 runtimeHost 对象
    // 以下写法的意思是 HResult hr = pfnGetCLRRuntimeHost(IID_ICLRRuntimeHost4, out var runtimeHost);
    Guid IID_ICLRRuntimeHost4 = new Guid("xxx-xxx-xx-xx-xxx"); // 当然了，实际写法是 EXTERN_GUID(IID_ICLRRuntimeHost4, 0x64F6D366, 0xD7C2, 0x4F1F, 0xB4, 0xB2, 0xE8, 0x16, 0x0C, 0xAC, 0x43, 0xAF); 只是这样写很诡异
    ICLRRuntimeHost4* runtimeHost;
    HRESULT hr = pfnGetCLRRuntimeHost(IID_ICLRRuntimeHost4, (IUnknown**)&runtimeHost);

    hr = runtimeHost->SetStartupFlags(/*一些不需要关注的启动配置*/);
    if (FAILED(hr))
    {
        printf("ERROR - Failed to set startup flags.\nError code:%x\n", hr);
        return -1;
    }

    // 启动运行时将会初始化 JIT 和 GC 和加载器等模块。运行到这里可以认为 dotnet 已经热完成了
    // Starting the runtime will initialize the JIT, GC, loader, etc.
    hr = runtimeHost->Start();

            // 进行创建 AppDomain 的配置
            int appDomainFlags = APPDOMAIN_ENABLE_PLATFORM_SPECIFIC_APPS | APPDOMAIN_ENABLE_PINVOKE_AND_CLASSIC_COMINTEROP | ... ;
            // 以下逻辑用 C++ 写，需要太多代码了，因此我就换 C# 系的代码来写
            // 哪些 dll 或 exe 将会被加入寻找程序集加载路径
            // 所有放在 coreRoot 路径下的 exe 和 dll 和 winmd 都会加入
            List<string> trustedPlatformAssemblies = DirectoryHelper.GetFiles(coreRoot, "*.exe|*.dll|*.winmd");

            var application = "c:\\lindexi\\Code\\HostWithMscoree\\dll\\ManagedLibrary.dll";

            string targetAppPath = Path.GetDirectoryName(application);

            // APP_PATHS
            // App paths are directories to probe in for assemblies which are not one of the well-known Framework assemblies
            // included in the TPA list.
            //
            // For this simple sample, we just include the directory the target application is in.
            // More complex hosts may want to also check the current working directory or other
            // locations known to contain application assets.
            string appPath = targetAppPath;
            List<string> appPaths = new List<string>() { appPath };

            // APP_NI_PATHS
            // App (NI) paths are the paths that will be probed for native images not found on the TPA list.
            // It will typically be similar to the app paths.
            // For this sample, we probe next to the app and in a hypothetical directory of the same name with 'NI' suffixed to the end.
            List<string> appNiPaths = new List<string>() { targetAppPath + ";" + targetAppPath + "NI" };

            // NATIVE_DLL_SEARCH_DIRECTORIES
            // Native dll search directories are paths that the runtime will probe for native DLLs called via PInvoke
            List<string> nativeDllSearchDirectories = new List<string>(){ appPath + ";" + coreRoot };
            List<string> platformResourceRoots = appPaths;

            // 这是传入的参数，参数是 Key 和 Value 对的，也就是下面的 propertyKeys 和 propertyValues 的值是一一对应的
            // Setup key/value pairs for AppDomain  properties
            string[] propertyKeys = new[]
            {
                "TRUSTED_PLATFORM_ASSEMBLIES",
                "APP_PATHS",
                "APP_NI_PATHS",
                "NATIVE_DLL_SEARCH_DIRECTORIES",
                "PLATFORM_RESOURCE_ROOTS"
            };

            // Property values which were constructed in step 5
            List<List<string>> propertyValues = new List<List<string>>()
            {
                trustedPlatformAssemblies,
                appPaths,
                appNiPaths,
                nativeDllSearchDirectories,
                platformResourceRoots
            };

            // 以上就是配置，拿到了 propertyKeys 和 propertyValues 组成了属性传入
            // 下面继续回到 C++ 代码

            hr = runtimeHost->CreateAppDomainWithManager(
                L"Sample Host AppDomain",       // Friendly AD name
            appDomainFlags,
            NULL,                           // Optional AppDomain manager assembly name
            NULL,                           // Optional AppDomain manager type (including namespace)
            sizeof(propertyKeys) / sizeof(wchar_t*),
            propertyKeys,
            propertyValues,
            &domainId);

    hr = runtimeHost->ExecuteAssembly(domainId, targetApp, argc - 1, (LPCWSTR*)(/*参数*/ NULL), &exitCode);

    runtimeHost->UnloadAppDomain(domainId, true /* Wait until unload complete */);
    runtimeHost->Stop();
    runtimeHost->Release();

// 加载 CoreClr.dll 文件
coreCLRModule = LoadCoreCLR(coreRoot);

// 拿到 GetCLRRuntimeHost 方法
FnGetCLRRuntimeHost pfnGetCLRRuntimeHost =
        (FnGetCLRRuntimeHost)::GetProcAddress(coreCLRModule, "GetCLRRuntimeHost");

// 使用 GetCLRRuntimeHost 方法拿到 runtimeHost 对象
HRESULT hr = pfnGetCLRRuntimeHost(IID_ICLRRuntimeHost4, (IUnknown**)&runtimeHost);

// 创建 AppDomain 对象
runtimeHost->CreateAppDomainWithManager(/*忽略代码*/ &domainId);

// 运行程序集
runtimeHost->ExecuteAssembly(domainId, targetApp);

// 清理
runtimeHost->UnloadAppDomain(domainId, true /* Wait until unload complete */);
runtimeHost->Stop();
runtimeHost->Release();