You can use something like GitHub or Conan to find specific useful C libraries.

There isn't a universally recognized "standard library replacement" (and people argue about what parts of the standard library they don't like), but here:

https://stackoverflow.com/questions/486383/safer-alternative...

are a few options:

* Glib (the basis for Gtk): https://developer.gnome.org/glib/stable/glib.html

* The Apache Portable Runtime (APR): http://apr.apache.org/

Caveat: I haven't used them.