MSVC 2022: C++ library build broken with UNICODE

[gpascualg]

When trying to build the c++ library while having UNICODE declared, the following error occurs:

palanteer-src\c++\palanteer.h(4346,53): error C2440: '=': cannot convert from 'const wchar_t [17]' to 'LPWSTR'

Basically, in that line, LogFile.LoggerName = KERNEL_LOGGER_NAME; the structure field expects a non-const value, while KERNEL_LOGGER_NAME is const. I have worked around it by casting it to (LPWSTR). I don't know the API exactly, so it feels like a hack to cast it to non-constness.

- LogFile.LoggerName          = KERNEL_LOGGER_NAME;
+ #if defined(_UNICODE) || defined(UNICODE)
+ LogFile.LoggerName          = (LPWSTR)KERNEL_LOGGER_NAME;
+ #else
+ LogFile.LoggerName          = KERNEL_LOGGER_NAME;
+ #endif

[dfeneyrou]

I was unable to reproduce this compilation issue with MSVC 2019 nor MSVC 2022 (installed it on purpose, only the "Build Tools"), when trying to build the test program.

In ./c++/testprogram/CMakeList.txt, the -DUNICODE is added by default, so I thought that it was linked to MSVC 2022.
With or without the addition of -DUNICODE , the type of the system constant KERNEL_LOGGER_NAME changes (LPSTR or LPWSTR) but is always consistent with the LoggerName type and I never got the const issue that you faced.

In short, in my case, both the actual code and your patch are working, also both for MSVC 2019 or 2022.
I used the command line nmake testprogram for all tests.

Can you give more details on your build setup and/or reproduce the issue with the provided test program (so with nmake testprogram)?

[gpascualg]

I'm currently away from home, but this Monday when I get back I'll build it and send you the outputs.
Thank you!

[BrodyHiggerson]

I've had the same issue in VS2019 v16.8.3 alongside a slew of warnings (will dig those out and open a separate issue listing them / a PR fixing them).

I'm using these flags:

/W4 /WX /std:c++latest /permissive- /D WIN32_LEAN_AND_MEAN /D NOMINMAX

Wonder if it's the permissive- (i.e. strict mode) flag.

My local fix was

LogFile.LoggerName = (char*)KERNEL_LOGGER_NAME;

[gpascualg]

Running nmake testprogram as is does, indeed, work. I have however isolated two instances that cause the error I was getting.

1. As @BrodyHiggerson says, adding /permissive- will trigger the error. I suspect the error is always there, just that without permissive the cast is being done implicitely.

add_compile_options(/permissive-)

2. Adding /std:c++20, which is my case. It seems enabling c++20 automatically enables strict conformance (permissive-).
   https://devblogs.microsoft.com/cppblog/msvc-cpp20-and-the-std-cpp20-switch/

add_compile_options(/std:c++20)

It definitely seems to be caused by strict mode.

Edit: I have not found any warning, though. So I don't know about them.

[dfeneyrou]

Thanks, I was able to reproduce it with /W4 /permissive- indeed!