导入模块的标准方式 [英] Standard way of importing modules

问题描述

我目前正在尝试在应同时在Windows(MSVC)和Linux(Clang和/或GCC)上编译的代码中使用c ++模块.

I am currently trying to use c++ modules in a code that should compile both on Windows (MSVC) and Linux (Clang and/or GCC).

我目前正在Visual Studio中进行开发，并使用标准符合模式"(/permissive-)使我的代码尽可能可移植.

I am currently developping in Visual Studio and used the "Standard Conformance Mode" (/permissive-) to make my code as portable as possible.

但是以下代码:

import std.core;
int main()
{
    std::cout << "Hello, World! haha" << std::endl;

    std::vector<int> myVec{4};

    std::map<std::string, size_t> myMap;

    return 0;
}

不能使用/permissive-标志进行编译.我收到以下错误:

Can not compile with the /permissive- flag. I get the following error:

E3223没有找到要导入的模块文件"std.core"

E3223 Cound not find module file "std.core" for import

错误C2664:'int _CrtDbgReport(int，const char *，int，const char*，const char *，...)':无法将参数4从'int'转换为'const char *'

error C2664: 'int _CrtDbgReport(int,const char *,int,const char *,const char *,...)': cannot convert argument 4 from 'int' to 'const char *'

我tought"std.core"可能是仅用于Windows的东西，因此我尝试了以下操作(我在许多示例中都看到了它):

I tought "std.core" might be a windows-only thing so i tried the following (i saw it in many examples) :

import <iostream>;
import <vector>;
import <map>;

但是会导致以下错误:

错误C7612:找不到以下文件的标头单元'PATH_TO_VS \ include \ iostream'

error C7612: could not find header unit for 'PATH_TO_VS\include\iostream'

错误C7612:找不到以下文件的标头单元'PATH_TO_VS \ include \ vector'

error C7612: could not find header unit for 'PATH_TO_VS\include\vector'

错误C7612:找不到"PATH_TO_VS \ include \ map"的标头单元

error C7612: could not find header unit for 'PATH_TO_VS\include\map'

注意:在PATH_TO_VS \ include中，实际上有名为"iostream"，"vector"和"map"的文件.

Note : There are actually files named "iostream", "vector", and "map" in PATH_TO_VS\include.

因此，我想知道导入c ++模块的标准方法是什么?如果"import std.core"是标准方式，为什么不使用/permissive-编译?

Therefore i'm wondering what is the standard way of importing c++ modules ? If "import std.core" is the standard way, why doesn't it compile with /permissive- ?

我正在使用Visual Studio 2019(社区)和CMake.

I am using Visual Studio 2019 (Community) and CMake.

对不起，我忘了告诉我的编译器标志:

Sorry i forgot to tell my compiler flags:

/experimental:module
/std:c++latest
/W4
/WX
/permissive-
/MDd
/EHsc

代码编译时不带/permissive-，但设置时不编译.我不知道为什么

The code compiles without /permissive-, but does not when it is set. I can't figure out why

推荐答案

根据Microsoft Docs，导入标头尚未实现.请参阅 https://docs.microsoft.com/en-us/cpp/cpp/modules-cpp?view=msvc-160#imported-header-files .

According to Microsoft Docs, import headers are not yet implemented. See https://docs.microsoft.com/en-us/cpp/cpp/modules-cpp?view=msvc-160#imported-header-files.

您可以在此处关注此功能的进度: https://github.com/microsoft/STL/issues/60 .

You can following the progress on this feature here: https://github.com/microsoft/STL/issues/60.

您可以在Visual Studio 2019中使用 import std.core; 语法(我在v16.8 +上对此进行了测试)，但是您还需要为以下安装" C ++模块"v142构建工具"Visual Studio安装程序中的组件才能正常工作.

You can use the import std.core; syntax in Visual Studio 2019 (I tested this with v16.8+) but you will also need to install the "C++ Modules for v142 build tools" component in the Visual Studio Installer for this to work.

此外，您将需要启用以下标志:

In addition, you will need to enable the following flags:

• /std:c ++ latest
• /experimental:module

如此答案所述.

在导入 std.core 模块时，您可能仍会收到一些有关不兼容环境的 C5050 警告:

You may still get some C5050 warnings about incompatible environment while importing the std.core module:

1>C:\Test\C++\Modules\main.cpp(1,16): warning C5050: Possible incompatible environment while importing module 'std.core': _GUARDOVERFLOW_CRT_ALLOCATORS=1 is defined in current command line and not in module command line
1>C:\Test\C++\Modules\main.cpp(1,16): warning C5050: Possible incompatible environment while importing module 'std.core': _DEBUG is defined in current command line and not in module command line
1>C:\Test\C++\Modules\main.cpp(1,16): warning C5050: Possible incompatible environment while importing module 'std.core': _M_FP_PRECISE is defined in current command line and not in module command line

1. 要解决第一个警告更改，请 SDL检查更改为否(/sdl-).
2. 要解决第二个警告，请删除 _DEBUG 预处理程序定义.
3. 要解决第三个警告，请删除浮点模型的值(在我的情况下，默认情况下设置为/fp:percise )./li>

1. To solve the first warning change SDL Checks to No (/sdl-).
2. To solve the second warning, remove the _DEBUG preprocessor definition.
3. To solve the third warning, delete the value of the Floating Point Model (which was, by default, set to /fp:percise in my case).

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