Avoid unnecessary `nextc()` recursion.

mrbgems/mruby-compiler/core/parse.y

@@ -3967,43 +3967,52 @@ static mrb_bool peeks(parser_state *p, const char *s);
 static mrb_bool skips(parser_state *p, const char *s);
 
 static inline int
-nextc(parser_state *p)
+nextc0(parser_state *p)
 {
   int c;
-
-  if (p->pb) {
-    node *tmp;
-
-    c = intn(p->pb->car);
-    tmp = p->pb;
-    p->pb = p->pb->cdr;
-    cons_free(tmp);
-  }
-  else {
 #ifndef MRB_DISABLE_STDIO
   if (p->f) {
-      if (feof(p->f)) goto eof;
+    if (feof(p->f)) return -1;
     c = fgetc(p->f);
-      if (c == EOF) goto eof;
+    if (c == EOF) return -1;
   }
   else
 #endif
     if (!p->s || p->s >= p->send) {
-        goto eof;
+      return -1;
     }
     else {
       c = (unsigned char)*p->s++;
     }
+  return c;
+}
+
+static inline int
+nextc(parser_state *p)
+{
+  int c;
+
+  if (p->pb) {
+    node *tmp;
+
+    c = intn(p->pb->car);
+    tmp = p->pb;
+    p->pb = p->pb->cdr;
+    cons_free(tmp);
+  }
+  else {
+    c = nextc0(p);
+    if (c < 0) goto eof;
   }
   if (c >= 0) {
     p->column++;
   }
   if (c == '\r') {
-    const int lf = nextc(p);
+    const int lf = nextc0(p);
     if (lf == '\n') {
       return '\n';
     }
-    pushback(p, lf);
+    if (lf > 0) pushback(p, lf);
   }
   return c;