pack.c: fix 'void*` to `char*` assignment.
@@ -974,8 +974,8 @@ static int
unpack_M(mrb_state *mrb, const void *src, int slen, mrb_value ary, unsigned int flags)
{
mrb_value buf = mrb_str_new(mrb, 0, slen);
- const char *s = src, *ss = s;
- const char *send = src + slen;
+ const char *s = (const char*)src, *ss = s;
+ const char *send = s + slen;
char *ptr = RSTRING_PTR(buf);
int c1, c2;
