What part of emacs displays parent folders at the top and how can I fix their symbols

Question

I updated spacemacs and all layers/ packages today. Since then, when in c++-mode at the top of my buffers the current file and its parent folders are displayed, as shown in the image.

I'm fine with the functionality but clearly there are some icons missing (as evidenced by the small squares containing "EsCC"). Where must I supply them?

This line seems to be a feature of c++ layer as it also displays c++ - specific info like class names and namespaces.

Here are all my layers, in case it helps:

 go
 systemd
 javascript
 rust
 html
 yaml
 vimscript
 csv
 markdown
 auto-completion
 (python :variables python-backend 'anaconda)
 octave
 better-defaults
 emacs-lisp
 helm
 (lsp :variables
      lsp-ui-doc-enable t
      lsp-ui-sideline-enable t)
 (c-c++ :variables
    c-c++-backend 'lsp-clangd
  c-c++-lsp-cache-dir ".cache"
  c-c++-enable-clang-support t
  clang-format-style "file")
  (cmake :variables
        cmake-backend 'lsp
        cmake-enable-cmake-ide-support t)

 multiple-cursors
 spell-checking
 syntax-checking
 latex
 julia
 restructuredtext
 json
 

Answer 1

After ignoring the issue and just working on my project I realized that it must be part of the c++ layer.

The solution for me is: You need to install additional fonts. What works, is installing all the fonts in the github repo of all-the-icons.