Make ResizeMemory do a full unsigned remainder to check for page size divisibility.

Author: sunfishcode

ml-proto/TestingTodo.md

@@ -49,6 +49,7 @@ Linear memory semantics:
  - test loading "uninitialized" things from aliased stack frames return what's there
  - test that loadwithoffset traps in overflow cases
  - test that newly allocated memory is zeroed
+ - test that resize_memory does a full 32-bit unsigned check for page_size divisibility
 
 Function pointer semantics:
  - test that function pointers work [correctly](https://github.com/WebAssembly/design/issues/89)

ml-proto/src/spec/eval.ml

@@ -222,7 +222,7 @@ let rec eval_expr (c : config) (e : expr) =
 
   | ResizeMemory e ->
     let i = int32 (eval_expr c e) e.at in
-    if (Int32.rem i (page_size c)) <> Int32.zero then
+    if (I32.rem_u i (page_size c)) <> I32.zero then
       error e.at "runtime: resize_memory operand not multiple of page_size";
     Memory.resize c.modul.memory (Int32.to_int i);
     None