Glib (https://developer.gnome.org/glib/2.60/glib-Miscellaneous-Mac...) is a great STL like library for C. It's got the basic data structures, a good API and plenty of utilities. My favorite is g_autoptr (https://developer.gnome.org/glib/stable/glib-Miscellaneous-M...) for deterministic cleanup. There's enough to make C a reasonably pleasant scripting language.