argp-fmtstream.c:377: warning: implicit declaration of function `vsnprintf' argp-help.c:1739: warning: #warning No reasonable value to return mempcpy.c:14: warning: no previous prototype for `mempcpy' strndup.c:15: warning: no previous prototype for `strndup' strchrnul.c:15: warning: no previous prototype for `strchrnul'