如何在VS2017中不使用/ Za编译一个文件（使用/ Za编译其余文件）？

Question

I want to be able to compile my VS2017 C++ project without Microsoft's language extension shenanigans.

Based on the replies here, /Za compiler directive does not compile system headers in VS2010 , is there a way to make VS compile one file without /Za, and the rest with?

The file that doesn't like the /Za flag in particular is Winnt.h, and several of my files are using it.

Answer 1

According to the Visual Studio devs:

The compiler switch /Za was an effort started decades ago to carve out a strictly portable behavior across several C++ compilers. The effort was stalled and we no longer recommend it for new projects. The switch /Za does not support certain key Microsoft SDK header files. By contrast /permissive- offers a useful conformance mode where input C++ code is interpreted according to ISO C++ rules but also allows conforming extensions necessary to compile C++ on targets supported by Visual C++. For example, you can use /permissive- with C++/CLI. The compiler switch /Za rejects a few non-conforming constructs; however the compiler switch /permissive- is our recommendation going forward for conforming code.

Therefore, compiling the whole project with /permissive- instead of trying to implement exceptions to single translation units using /Za might be an acceptable payoff between being conformant to ISO-C++ and being able to compile non-standard Microsoft header files. Furthermore, you can disable more extensions by making use of the /Zc flag and its options:

The compiler switches /Zc:strictStrings and /Zc:rvalueCast are currently off by default, allowing non-conforming behavior. The switch /permissive- turns them on by default. You can pass in the /Zc flags after /permissive- to override this behavior if needed.

Answer 2

This was painfully simpler than I realised.

1. Right click the project in Solution Explorer, go to Properties -> C\\C++ -> Language -> Disable Language Extensions -> Yes (/Za)
2. Hit OK.

Now whatever new files you add will use /Za.

3. Hold Shift and select all the files you need to not use /Za.
4. Repeat Step 1 except now set Disable Language Extensions to No.

Now only those files will build with Microsoft's language extensions.

No mucking around with vcxproj editing (and the filters hassle it creates), no having to set files to stop inheriting from project defaults, no messing with /Ze or /Zc or any manual command line jimmying. The amount of time I wasted not realising how simple this was. >_<

A few other notes: Thanks to the suggestions here and pushing & pulling various levers, I have found the following:

• The /permissive- command line option, discussed on the Visual C++ Team Blog (thanks Jodocus) apparently does what I needed. However I found it simply didn't catch an anonymous struct, so perhaps I've done something wrong but it wasn't forcing my code into ISO C++ conformance.

• The /Zc compiler options don't mention anonymous structures, so if one of them catches non-conforming anonymous structs, I can't tell which. Since that's one thing from ISO C++ I can't find explicitly covered, I lost faith in these flags also.

• If the offending file is a header file, you have to disable that /Za for every source file that includes that offending header.

• Finally, this can also be done programmatically instead. See DisableLanguageExtensions .

Answer 3

Technically speaking, this is how you assign some metadata to a whole group of files, but ignore it in one file using MSBuild:

 <ItemGroup> <Compile Include="**\\*.cpp" Exclude="foo.cpp"> <SomeCompilerSettingMetaData>/Za</SomeCompilerSettingMetaData> </Compile> <Compile Include="foo.cpp" > <SomeCompilerSettingMetaData></SomeCompilerSettingMetaData> </Compile> </ItemGroup> 

I don't remember what compiler setting /Za will get assigned to, and it doesn't matter for the purposes of this illustration. The point is the Include and Exclude attributes on the Items list should exclude and include the file you want to single out for special settings. Notice in the last one that the compiler setting you are looking at is absent.