Replace mrb_fixnum_value() with mrb_int_value().

Use `mrb_fixnum_value()` only when you are absolutely sure that the
value is within `Fixnum` range, i.e. 31 bits signed integer at least.

src/array.c

@@ -1083,7 +1083,7 @@ mrb_ary_index_m(mrb_state *mrb, mrb_value self)
 
   for (i = 0; i < RARRAY_LEN(self); i++) {
     if (mrb_equal(mrb, RARRAY_PTR(self)[i], obj)) {
-      return mrb_fixnum_value(i);
+      return mrb_int_value(mrb, i);
     }
   }
   return mrb_nil_value();
@@ -1097,7 +1097,7 @@ mrb_ary_rindex_m(mrb_state *mrb, mrb_value self)
 
   for (i = RARRAY_LEN(self) - 1; i >= 0; i--) {
     if (mrb_equal(mrb, RARRAY_PTR(self)[i], obj)) {
-      return mrb_fixnum_value(i);
+      return mrb_int_value(mrb, i);
     }
     if (i > (len = RARRAY_LEN(self))) {
       i = len;
@@ -1136,7 +1136,7 @@ mrb_ary_size(mrb_state *mrb, mrb_value self)
 {
   struct RArray *a = mrb_ary_ptr(self);
 
-  return mrb_fixnum_value(ARY_LEN(a));
+  return mrb_int_value(mrb, ARY_LEN(a));
 }
 
 MRB_API mrb_value

src/error.c

@@ -286,7 +286,7 @@ mrb_vformat(mrb_state *mrb, const char *format, va_list ap)
 #else
           i = *p == 'd' ? (mrb_int)va_arg(ap, int) : va_arg(ap, mrb_int);
 #endif
-          obj = mrb_fixnum_value(i);
+          obj = mrb_int_value(mrb, i);
           goto L_cat_obj;
 #ifndef MRB_NO_FLOAT
         case 'f':

src/numeric.c

@@ -180,7 +180,7 @@ int_idiv(mrb_state *mrb, mrb_value x)
   if (y == 0) {
     int_zerodiv(mrb);
   }
-  return mrb_fixnum_value(mrb_integer(x) / y);
+  return mrb_int_value(mrb, mrb_integer(x) / y);
 }
 
 static mrb_value

src/string.c

@@ -893,14 +893,14 @@ static mrb_value
 mrb_str_size(mrb_state *mrb, mrb_value self)
 {
   mrb_int len = RSTRING_CHAR_LEN(self);
-  return mrb_fixnum_value(len);
+  return mrb_int_value(mrb, len);
 }
 
 static mrb_value
 mrb_str_bytesize(mrb_state *mrb, mrb_value self)
 {
   mrb_int len = RSTRING_LEN(self);
-  return mrb_fixnum_value(len);
+  return mrb_int_value(mrb, len);
 }
 
 /* 15.2.10.5.1  */
@@ -1014,7 +1014,7 @@ mrb_str_cmp_m(mrb_state *mrb, mrb_value str1)
   else {
     result = mrb_str_cmp(mrb, str1, str2);
   }
-  return mrb_fixnum_value(result);
+  return mrb_int_value(mrb, result);
 }
 
 static mrb_bool
@@ -1235,7 +1235,7 @@ str_replace_partial(mrb_state *mrb, mrb_value src, mrb_int pos, mrb_int end, mrb
   if (end > len) { end = len; }
 
   if (pos < 0 || pos > len) {
-    str_out_of_index(mrb, mrb_fixnum_value(pos));
+    str_out_of_index(mrb, mrb_int_value(mrb, pos));
   }
 
   replen = (mrb_nil_p(rep) ? 0 : RSTRING_LEN(rep));
@@ -1820,7 +1820,7 @@ mrb_str_index_m(mrb_state *mrb, mrb_value str)
 
   if (pos == -1) return mrb_nil_value();
   BYTES_ALIGN_CHECK(pos);
-  return mrb_fixnum_value(pos);
+  return mrb_int_value(mrb, pos);
 }
 
 /* 15.2.10.5.24 */
@@ -2049,7 +2049,7 @@ mrb_str_rindex(mrb_state *mrb, mrb_value str)
   if (pos >= 0) {
     pos = bytes2chars(RSTRING_PTR(str), RSTRING_LEN(str), pos);
     BYTES_ALIGN_CHECK(pos);
-    return mrb_fixnum_value(pos);
+    return mrb_int_value(mrb, pos);
   }
   return mrb_nil_value();
 }