Well-known developer, Keith Packard has recently announced the launch of “picolibc” through his blog. Picolibc is a C Library for embedded systems which is suitable for small micro-controllers, and this standard C library API’s allows to run even in low memory (RAM) devices. This is an upgraded version of “newlib-nano” with few interesting changes which includes replacement of “stdio” lib with ATMEL-specific printf code adopted from avrlibc. As part of this library, Keith also launched picocrt, which is responsible for initializing memory and invoking various constructors before calling its own C program, the main function.
article: https://www.cnx-software.com/2019/10/03/picolibc-lightweight-c-library-embedded-systems/