C++ initialization is tricky. Check out Abseil's C++ Tips on initialization, which we've published over the past two weeks:

• Tip of the Week #61: Default Member Initializers

• Tip of the Week #88: Initialization: =, (), and {}

• Tip of the Week #134: make_unique and private constructors

• Tip of the Week #142: Multi-parameter Constructors and `explicit`

Fro​m Tip of the Week #142:

"Prior to C++11, the explicit keyword was meaningful only for constructors that could be called with a single argument, and our style guide required its use for such constructors so that they did not act as 'converting constructors.' That requirement was not applied for multi-parameter constructors. Indeed the style guide used to discourage use of explicit for multi-parameter constructors as it had no meaning. That’s no longer the case."