lib: string: implement mempcpy

mempcpy(3) is a GNU libc extension that like stpcpy returns not the
start of the destination buffer, but the first byte after its end.

Provide it as it is useful when concatenating buffers or known-size
strings.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20221101064310.3227410-1-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/string.h b/include/string.h
index d423bee6fb..499f2ec03c 100644
--- a/include/string.h
+++ b/include/string.h
@@ -4,6 +4,7 @@
 
 #include <linux/string.h>
 
+void *mempcpy(void *dest, const void *src, size_t count);
 int strtobool(const char *str, int *val);
 char *strsep_unescaped(char **, const char *);
 char *stpcpy(char *dest, const char *src);