How can I add exsiting c++ vs project made by SLT into unreal project?

I try to add existing visual studio project made by STL into unreal project. I cannot find the way. Could you share some answers?

UE4 is using normal C++ compiled by VS compiler and can do everything that C++ can as long as it’s configured right in build script.

Standard Library is usable by default (as UE4 it self use it), but you should not do that or else you know what you doing. Main reason is UE4 have massive wrapper code (some are straight up reimplementations like container types), which allows easy portability of the code to different platforms as long as UE4 supports it, it also provides optimizations for those platforms. If you use standard library there no guarranty it will build on specific platform (but it should on desktop systems).

2nd which is consequence of first, UE4 APIs don’t support standard library, in order to use those with it you will need to make wrapper class which will convert those types.

But either way UBT should able to build the STL code, all you need to do, i just copy code files to the module, UBT will catch them and try to compile them, if there anything missing in depeces you can configure things such include directories in build script.

You could also turn your code in to library and then make a module to support it in UE4, there should be a lot more tutorials on that.