# Freestanding C Headers

This subtree defines headers required for a C freestanding implementation, as
specified in S4p6 of the C11 standard. Said headers are implemented *to the
letter* as described in respective sections of said standard. These headers
must be substitutable for those provided by the system toolchain when building
for host-side code, so that includes of these headers do not cause breakage
when building on host-side, where these headers are *never* included.

All of `sw/device` is compiled using only these headers, and this directory acts
as the sole root against which `#include <...>` directives are resolved.
Headers provided by the system or the compiler are totally inaccessible and
should not be used. Conversely, these headers must *never* be included via
their full paths, since they can easily clash with the corresponding headers
provided by the host-side toolchain, as described above.

These headers are guaranteed to be compatible with processors and compilers
implementing the RISC-V ILP32 psABI, though they may be compatible with other
architectures and calling conventions on a best-effort basis.
However, compilers *must* be compatible with Clang and GCC's intrinsics.