char *hexmem(const void *p, size_t l);
void *unhexmem(const char *p, size_t l);
-char *strextend(char **x, ...);
+char *strextend(char **x, ...) _sentinel_;
char *strrep(const char *s, unsigned n);
void* greedy_realloc(void **p, size_t *allocated, size_t need);