The best way to handle config in large C++ project

Question

In order to start my C++ program, I need to read some configs, e.g. ip address, port number, file paths... These settings may change quite frequently (every week or everyday!), so hardcoding them into source files is not a good idea.

After some research, I'm confused about whether there is a best practice to load config settings from a file and made those configs available to other class/module/*.cpp in the same project.

static is bad; singleton is bad (an anti-pattern?) So, what other options do we have? Or, maybe the idea of "config file" is wrong?

EDIT: I have no problem of loading the config file. I'm worried about, after loading all those settings into a std::map< string, string > in memory, how to let other classes, functions access those settings.

EDIT 2: Thanks for everybody's input. I know these patterns that I listed here are FINE, and they are used by lots of programs. I'm curious about whether there is a (sort of) BEST pattern to handle configurations of a program.

Answer 1

Arguably, a configuration file is a legitimate use for a Singleton. The Singleton pattern is usually frowned upon because Singletons cause problems with race conditions in a multi-threaded environment, and since they're globally accessible, you run into the same problems you have with globals. But if your Singleton object is initialized once when you read in the config file, and never altered after that, I can't think of a legitimate reason to call it an "anti-pattern" other than some sort of cargo-cult mentality.

That being said, when I need to make a configuration file available as an object to my application, I don't use a Singleton. Usually I pass the configuration object around to those objects/functions which need it.