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About microlib

Microlib is an alternative library to the default C library. It is intended for use with deeply embedded applications that must fit into extremely small memory footprints.

These applications do not run under an operating system.


  • Microlib does not attempt to be an ISO C-compliant library.
  • Microlib has no support for AArch64 execution state.

Microlib is highly optimized for small code size. It has less functionality than the default C library and some ISO C features are completely missing. Some library functions are also slower.

Functions in microlib are responsible for:

  • Creating an environment that a C program can execute in. This includes:

    • Creating a stack.

    • Creating a heap, if required.

    • Initializing the parts of the library the program uses.

  • Starting execution by calling main().