The Cosmopolitan Libc memcpy() implementation is still binary compatible with the System V Application Binary Interface (x86_64 Processor Supplement). It gains

The Cosmopolitan Libc memcpy() implementation is still binary compatible with the System V Application Binary Interface (x86_64 Processor Supplement). It gains the performance by restricting itself to a subset of the ABI, which the optional memcpy() macro is able to take advantage of. For example, the macro trick isn't even defined in strict ANSI mode.