musl libc

musl, pronounced like the word "mussel", is an MIT-licensed
implementation of the standard C library targetting the Linux syscall
API, suitable for use in a wide range of deployment environments. musl
offers efficient static and dynamic linking support, lightweight code
and low runtime overhead, strong fail-safe guarantees under correct
usage, and correctness in the sense of standards conformance and
safety. musl is built on the principle that these goals are best
achieved through simple code that is easy to understand and maintain.

The 1.1 release series for musl features coverage for all interfaces
defined in ISO C99 and POSIX 2008 base, along with a number of
non-standardized interfaces for compatibility with Linux, BSD, and
glibc functionality.

For basic installation instructions, see the included INSTALL file.
Information on full musl-targeted compiler toolchains, system
bootstrapping, and Linux distributions built on musl can be found on
the project website:

    http://www.musl-libc.org/


[Echelon fork notes]
  This fork adds some features that can be enabled with configure
  switches:
    --enable-nommu-error

  Configure switch: --enable-nommu-error
    This switch causes calls to some system call wrappers that are either
    entirely incompatible with or are detected to be used in a NoMMU
    incompatible way to return an error instead of making the call to the
    kernel.  This is intended to be used to detect where programs attempt
    to use NoMMU incompatible calls that would otherwise result in
    difficult to diagnose bugs.

    The system calls which are currently supported:
      fork  - returns ENOSYS always
      clone - returns EOPNOTSUPP if flags not CLONE_VM
      mmap  - returns EOPNOTSUPP if flags not MAP_ANONYMOUS/MAP_ANON and
              either MAP_SHARED or MAP_SHARED_VALIDATE