Plan 9 from Bell Labs’s /usr/web/sources/patch/maybe/ape-vsnprintf/vfprintf.c
/* * pANS stdio -- vfprintf */ #include "iolib.h" int vfprintf(FILE *f, const char *s, va_list args) { int ret = _vfprintf(f,s,args); return ferror(f) ? -1 : ret; }