The libc can used in two different modes:
- The overlay mode: In this mode, the link order semantics are exploited to overlay implementations from LLVM's libc over the system libc. See :ref:`overlay_mode` for more information about this mode.
- The fullbuild mode: In this mode, LLVM's libc is used as the only libc for the binary. See :ref:`fullbuild_mode` for information about this mode.