Add mempcpy implementation

A GNU extension that returns dst + size instead of dst. It's a nice
shortcut when copying strings with a known size or back-to-back blocks
and you have to do it often.

May of course be called directly or alternately through
__builtin_mempcpy in some compiler versions.

For ASM on native targets, it is implemented as an alternate entrypoint
to memcpy which adds minimal code and overhead.

Change-Id: I4cbb3483f6df3c1007247fe0a95fd7078737462b

1 files changed, 1 insertions, 0 deletions

diff --git a/firmware/libc/include/string.h b/firmware/libc/include/string.h
index 9346611aee..9815c62805 100644
--- a/firmware/libc/include/string.h
+++ b/firmware/libc/include/string.h
@@ -20,6 +20,7 @@ extern "C" {
 _PTR     _EXFUN(memchr,(const _PTR, int, size_t));
 int      _EXFUN(memcmp,(const _PTR, const _PTR, size_t));
 _PTR     _EXFUN(memcpy,(_PTR, const _PTR, size_t));
+_PTR     _EXFUN(mempcpy,(_PTR, const _PTR, size_t));
 _PTR     _EXFUN(memmove,(_PTR, const _PTR, size_t));
 _PTR     _EXFUN(memset,(_PTR, int, size_t));
 char    *_EXFUN(strcat,(char *, const char *));