Using C++ standard library in dll internally

Question

I have read in many places that you should never use C++ standard library classes in the api of a shared library. Now what I am unsure about is whether it is safe to use a standard library class like std::vector in a dll privately, and only expose a pointer to the data.

I am trying to create a dll that will dynamically be loaded at runtime, does this change anything?

Also do I need to worry about how I will link the standard library to the dll? Is that consistent across platforms?

Answer 1

Yes, it is generally considered bad practice to use non-POD data types across the DLL boundary. Bad things happen when the calling module uses different versions/implementations of the data types that the DLL's public API uses (ie, when the calling module uses a different version of the same compiler/framework that the DLL uses). Or, even when the calling module doesn't support the data types at all (ie, when the calling module is written in a completely different compiler/language than the DLL is written in).

When sharing DLLs, you should design the public API as though it were targeting the C language only, as that is the most portable option amongst various compilers/languages that support accessing DLLs.

However, the DLL can freely use whatever it wants internally for its private implementations. Just don't expose those details publicly.