[cppia] Fix int overflow in arithmetic assignments (#1258)

* [cppia] Fix int overflow in arithmetic assignments

Currently, the cppia interp runtime uses float operations for arithmetic
assignments such as *=. This results in inconsistent int overflow
behaviour.

* [tests] Add regression test for int *= overflow

Author: tobil4sk

src/hx/cppia/Cppia.h

@@ -1083,6 +1083,14 @@ struct NAME \
       ioVal  = left OP f; \
       return ioVal; \
    } \
+   inline static int &run(int &ioVal, hx::CppiaCtx *ctx, hx::CppiaExpr *value) \
+   { \
+      int left = ioVal; \
+      int i = value->runInt(ctx); \
+      BCR_CHECK_RET(ioVal); \
+      ioVal  = left OP i; \
+      return ioVal; \
+   } \
    static bool run(bool &ioVal, hx::CppiaCtx *ctx, hx::CppiaExpr *value) { value->runVoid(ctx); return ioVal; } \
    static String run(String &ioVal, hx::CppiaCtx *ctx, hx::CppiaExpr *value) { value->runVoid(ctx); return ioVal; } \
    static hx::Object *run(hx::Object * &ioVal, hx::CppiaCtx *ctx, hx::CppiaExpr *value) \

test/cppia/Client.hx

@@ -197,6 +197,14 @@ class Client
          return;
       }
 
+      // regression test for #1257
+      var x = 1290555;
+      x *= 1290555;
+      if (x != -915102823) {
+         Common.status = 'Failed regression test for #1257. x: $x';
+         return;
+      }
+
       final extending = new ClientExtendedExtendedRoot();
 
       extending.addValue();