The number of people this effects seems like it must be pretty small. There's the subset of people that have more than one OS. There's the subset of those that use command line tools (this explicitly doesn't do GUIs). There's the subset of those that would even think about some convenience of downloading a single binary command-line tool for multiple-OSes rather than use (a) something compiled specifically for that OS or (b) using something specific to that OS (rmdir on windows, rm on linxu/mac).

I use git, I've never felt especially put out that it's a different executable on mac, windows, and linux (situation "a"). I also just use what's common for the OS I'm on since there's so may other differences (C:\foo/bar) vs (/foo/bar) etc... (situation b)

You feel comfortable with git because someone put a lot of work into making its source code and ecosystem portable.

https://github.com/search?q=repo%3Agit%2Fgit+WIN32+OR+mingw+...

If no one had done that work, you'd have to port it yourself.

Cosmo provides a development environment that can ease this work. It's not only about the fat binary.

That's a good point. I guess I'd be more likely to pick some library because even if the binary is portable, the OS is not. Understanding where to store user preferences for example. (unix usually puts them in ~/.somefolder but on Windows it's somewhere in LocalAppData and on mac it's often in ~/Application Support). Understanding that paths have different parts, ... I'm sure there's more.

I don't know to what level C++20 does all this now with filesystem and threads etc... There's also things like libuv, Abseil, etc. But, maybe I'll check out cosmo next.

There are all sorts of issues in trying to come up with a single abstraction for multiple platforms. It's an impedance mismatch problem, there is no single best solution.

I like where cosmo is putting effort. The self-hosting toolchain and build system for example. That was always a knowledge barrier for me (I'm a webdeveloper, I know nothing).

Personally, it was so different and shocking, that I started to understand a lot of things by the contrast it created with other code. Cosmos's Makefiles were different, the linker was being used in a way that made me notice it as a distinct part of the toolchain, the demos actually worked, etc. It made me interested in that stuff, made it more acessible.

Even if you have to do some runtime detection/self-configuration, cosmo is great because it lets you pack that logic into a single binary and pick it at runtime, so the user experience is still "download a single file and run it and it works" regardless of their OS.