The kernel currently provides only the minimal subset of the standard C library required to meet the kernel's own needs, primarily in the areas of string manipulation and display.
Applications that require a more extensive C library can either submit contributions that enhance the existing library or substitute with a replacement library.
The Zephyr SDK and other supported toolchains comes with a bare-metal C library based on newlib
that can be used with Zephyr by selecting the CONFIG_NEWLIB_LIBC
in the application configuration file. Part of the support for newlib
is a set of hooks available under lib/libc/newlib/libc-hooks.c
which integrates the c library with basic kernel services.