How to find out the implementation details for a certain standard C++ function?

Let's look for example at std::normal_distribution.

I know that there is a handful of algorithms to sample from a normal distribution (reference: Wikipedia). And I know that the STL specification usually leaves it to the implementation to choose the algorithm (reference: SO).

However, it is sometimes required to specify which algorithm is in use under the hood. How to find out the details about the implementation?

(I admit that I don't know much about the different STL implementations that exist in this world. Mostly, I'm using the ones shipped with XCode/clang, gcc and MSVC.)