This directory contains partial re-implementations of some C++ standard library utilities. They are for use with internal LLVM libc code and tests.

More utilities can be added on an as-needed basis. There are certain rules to be followed for future changes and additions:

• Only certain kind of headers can be included:

  • Other headers from this directory
  • Free-standing C headers (<stdint.h> et al)
  • A few basic src/__support/macros headers used pervasively in all libc code

• Free-standing C headers are to be included as C headers and not as C++ headers. That is, use #include <stddef.h> and not #include <cstddef>. The proxies can also be used, as in #include "hdr/stdint_proxy.h".

• The utilities should be defined in the namespace LIBC_NAMESPACE::cpp. The higher level namespace should have a __ prefix to avoid symbol name pollution when the utilities are used in implementation of public functions.

• Each “CPP/foo.h” provides an exact subset of the API from standard C++ , just using LIBC_NAMESPACE::cpp::foo names in place of std::foo names. The implementations here need not be perfect standard-conforming implementations, but their behavior must match for whatever is supported at compile time. That is, if each were just declared with using std::foo; all the libc code should work the same (functionally speaking, excluding namespace entanglements).

• Additional APIs specific to libc internals belong elsewhere in src/__support, not in src/__support/CPP.