Merge pull request #2068 from cremno/exc_inspect-convert-mesg-to-string

convert exception message to string

src/error.c

@@ -127,7 +127,12 @@ exc_inspect(mrb_state *mrb, mrb_value exc)
   mesg = mrb_attr_get(mrb, exc, mrb_intern_lit(mrb, "mesg"));
   file = mrb_attr_get(mrb, exc, mrb_intern_lit(mrb, "file"));
   line = mrb_attr_get(mrb, exc, mrb_intern_lit(mrb, "line"));
-  append_mesg = !mrb_nil_p(mesg) && RSTRING_LEN(mesg) > 0;
+
+  append_mesg = !mrb_nil_p(mesg);
+  if (append_mesg) {
+    mesg = mrb_obj_as_string(mrb, mesg);
+    append_mesg = RSTRING_LEN(mesg) > 0;
+  }
 
   if (!mrb_nil_p(file) && !mrb_nil_p(line)) {
     str = mrb_str_dup(mrb, file);
@@ -144,14 +149,14 @@ exc_inspect(mrb_state *mrb, mrb_value exc)
     }
   }
   else {
-    str = mrb_str_new_cstr(mrb, mrb_obj_classname(mrb, exc));
+    const char *cname = mrb_obj_classname(mrb, exc);
+    str = mrb_str_new_cstr(mrb, cname);
+    mrb_str_cat_lit(mrb, str, ": ");
     if (append_mesg) {
-      mrb_str_cat_lit(mrb, str, ": ");
       mrb_str_append(mrb, str, mesg);
     }
     else {
-      mrb_str_cat_lit(mrb, str, ": ");
-      mrb_str_cat_cstr(mrb, str, mrb_obj_classname(mrb, exc));
+      mrb_str_cat_cstr(mrb, str, cname);
     }
   }
   return str;