Modify handling of integer literal.

Do not assume that significand of `double` is larger than `mrb_int`.

src/codegen.c

@@ -959,6 +959,48 @@ readint_float(codegen_scope *s, const char *p, int base)
   return f;
 }
 
+static mrb_int
+readint_mrb_int(codegen_scope *s, const char *p, int base, int neg, int *overflow)
+{
+  const char *e = p + strlen(p);
+  mrb_int result = 0;
+  int n;
+
+  if (*p == '+') p++;
+  while (p < e) {
+    char c = *p;
+    c = tolower((unsigned char)c);
+    for (n=0; n<base; n++) {
+      if (mrb_digitmap[n] == c) {
+	break;
+      }
+    }
+    if (n == base) {
+      codegen_error(s, "malformed readint input");
+    }
+
+    if (neg) {
+      if ((MRB_INT_MIN + n)/base > result) {
+        *overflow = TRUE;
+        return 0;
+      }
+      result *= base;
+      result -= n;
+    }
+    else {
+      if ((MRB_INT_MAX - n)/base < result) {
+        *overflow = TRUE;
+        return 0;
+      }
+      result *= base;
+      result += n;
+    }
+    p++;
+  }
+  *overflow = FALSE;
+  return result;
+}
+
 static void
 codegen(codegen_scope *s, node *tree, int val)
 {
@@ -1733,18 +1775,18 @@ codegen(codegen_scope *s, node *tree, int val)
     if (val) {
       char *p = (char*)tree->car;
       int base = (intptr_t)tree->cdr->car;
-      double f;
       mrb_int i;
       mrb_code co;
+      int overflow;
 
-      f = readint_float(s, p, base);
-      if (!FIXABLE(f)) {
+      i = readint_mrb_int(s, p, base, FALSE, &overflow);
+      if (overflow) {
+	double f = readint_float(s, p, base);
 	int off = new_lit(s, mrb_float_value(f));
 
 	genop(s, MKOP_ABx(OP_LOADL, cursp(), off));
       }
       else {
-	i = (mrb_int)f;
 	if (i < MAXARG_sBx && i > -MAXARG_sBx) {
 	  co = MKOP_AsBx(OP_LOADI, cursp(), i);
 	}
@@ -1789,18 +1831,18 @@ codegen(codegen_scope *s, node *tree, int val)
         {
           char *p = (char*)tree->car;
           int base = (intptr_t)tree->cdr->car;
-	  mrb_float f;
           mrb_int i;
           mrb_code co;
+          int overflow;
 
-	  f = readint_float(s, p, base);
-	  if (!FIXABLE(f)) {
+          i = readint_mrb_int(s, p, base, TRUE, &overflow);
+          if (overflow) {
+	    double f = readint_float(s, p, base);
 	    int off = new_lit(s, mrb_float_value(-f));
-	    
+
 	    genop(s, MKOP_ABx(OP_LOADL, cursp(), off));
 	  }
 	  else {
-	    i = (mrb_int)-f;
 	    if (i < MAXARG_sBx && i > -MAXARG_sBx) {
 	      co = MKOP_AsBx(OP_LOADI, cursp(), i);
 	    }