ref: b1a79e9db4d453d99bcf171c57f1734c1c3ebef8
dir: /sys/src/libString/s_putc.c/
#include <u.h>
#include <libc.h>
#include "String.h"
void
s_putc(String *s, int c)
{
if(s->ref > 1)
sysfatal("can't s_putc a shared string");
if (s->ptr >= s->end)
s_grow(s, 2);
*(s->ptr)++ = c;
}