Glad to read it!
I have only gcc as compiler, at least, it is what codeblocks suggests to me when I launch it.
gcc version 6.2.1 20160830 (GCC)
My running OS is archlinux and I have codeblocks 16.01
I found out that all C libraries were contained in the folder /usr/include
Edit:
After taking the time to read what was written in the popup when I launch codeblocks, I have the feeling that the IDE is not correctly configured.
I join a screenshot for more details.
I tried to navigate in settings and menus but all of that is a bit confusing and not really explicit for me.
Thank you for your help.