Have you actually tried to get YouCompleteMe[1] to work for C/C++ autocomplete? It's a huge PIA. Autocomplete just works in VSCode and many other IDEs once you point them at the right directory.
I'm a front end web dev who decided to learn C (the other week actually). Took about 5 minutes to download and install YouCompleteMe.. What problems did you have?
The one problem I had was that I had to use the system version of clang as I'm using Arch.
Basically I am not able to compile my particular codebase in clang or gcc too easily since it's an embedded system. But many other IDEs have no problem inferring autocompletion without requiring compilation.
YouCompleteMe itself was a bit of an issue as I have to develop in Windows and it's not quite as well supported.
Having to compile YCM for on an embedded system sounds like quite the corner case, and I can certainly see why you might have issues.
That said, there is a fair bit of built-in auto completion in vanilla vim (on par with VSC), and a few quick rebinds might be all you need. I would suggest checking it out.
:help 24.3
(I wish it were indexed a bit better in the help files. :/ )
You should use a different completion plugin then. YCM is the only one that needs to be compiled. If you use regular vim, check out neocomplete, and if you use neovim, well, you should know about deoplete (it's kickass). Both of these pretty much work out of the box; they have accompanying clang sources (vim-clang or deoplete-clang) that feed the suggestions to neocomplete/deoplete.
Frankly, I would use neovim + deoplete. Modern, async, and a big user community right now (almost everyone with neovim runs deoplete).
Given that I am currently a windows user on visual studio, I'm not exactly sure how I would get started with neovim and deoplete. The instructions on deoplete [0] assume you're not running on windows, to start, and looking in the issues [1] It's not supported
I use YouCompleteMe for all my autocompleting needs (Python, Go, Rust, C) and it works quite well for me. My experience was that it was literally as easy as (copying the command straight from my shell history):
https://github.com/Valloric/YouCompleteMe