rapidjson | fast JSON parser/generator for C with both SAX/DOM style

C++ versions are largely backwards compatible with prior versions. Any incompatibility are (usually) done for a specific purpose and with some degree of deprecation or the like.

So broadly speaking, a C++11 library (header-only or compiled) will compile under a C++17 compiler. There are times when this will fail, but they're usually around specific library types (like std::auto_ptr or somesuch).

For compiled libraries, ABI can be an issue (which means you may need to recompile them, which requires the source code). But for header-only libraries, this isn't a problem, since you're always compiling them.

I think you need to use conversion here, I have go through the doc and src of RapidJSON, and confirmed that we can't mix GenericValue with Value.

We can use the wstring_convert, see this answer as the reference.

Or with boost.

You can use FileReadStream and ParseStream instead of the IStreamWrapper. According to the documentation, FileReadStream is much faster than IStreamWrapper.

The R means that it's a raw string literal. Without it, the backslashes are interpreted as the start of escape sequences and you would have to write it like this to make it correct:

The AuthKey variable set in the docker run command will not affect the Server.cfg in the already created image from the docker build. At that point the image was already created with the file. You could solve that with a build arg, but that would result in what is normally a secret value and configuration data included in the image, which is an anti-pattern.

Instead, I'd probably start by running the https://github.com/BeamMP/BeamMP-Server in your current repo and checkout your desired tag there, making it a git submodule. When cloning your repo you'd then include submodules with git clone --recurse-submodules. Then the Dockerfile just has a copy of that directory.

After that, I would completely skip the creation of the Server.cfg inside of docker, or move that to an entrypoint that uses injected environment variables. Doing this outside of docker would involve creating the config file and mounting it as a volume. Performing the creation of this in the entrypoint could look like:

This part of the code doesn't do anything:

Converted OP's comment to an answer:

The precision was set at 1, that's the reason you are getting this output. So set the precision to 18 and this issue should be solved.

The arguments to std::visit (value) should be std::variants but seems to be a std::pair.

Example:

So is it legal in C++?

No, it isn't legal in c++ (Wikipedia also already stated "While not allowed by C++ ...").

In c++ a union is just reserving memory for the contained union members, such that it is enough to fit the largest member. That memory is shared by all members.

Accessing a different member from the union as was used to initialize it, is undefined behavior. You need to decide beforehand with which union members to work, if these are shared by any functions (this is often done using a type discriminator).