fix possible bug

Author: CAG2Mark

hkmc2/shared/src/main/scala/hkmc2/codegen/StackSafeTransform.scala

@@ -83,6 +83,7 @@ class StackSafeTransform(depthLimit: Int)(using State):
       ) :: Nil,
       blockBuilder
         .assignFieldN(predefPath, STACK_LIMIT_IDENT, intLit(depthLimit)) // set stackLimit before call
+        .assignFieldN(predefPath, STACK_OFFSET_IDENT, intLit(0)) // set stackOffset = 0 before call
         .assignFieldN(predefPath, STACK_DEPTH_IDENT, intLit(1)) // set stackDepth = 1 before call
         .assignFieldN(predefPath, STACK_HANDLER_IDENT, handlerSym.asPath) // assign stack handler
         .rest(HandleBlockReturn(res)),

hkmc2/shared/src/test/mlscript/handlers/StackSafety.mls

@@ -147,6 +147,7 @@ hi(0)
 //│     toString() { return "Cont$(" + this.pc + ")"; }
 //│   };
 //│   globalThis.Predef.__stackLimit = 5;
+//│   globalThis.Predef.__stackOffset = 0;
 //│   globalThis.Predef.__stackDepth = 1;
 //│   globalThis.Predef.__stackHandler = stackHandler;
 //│   res1 = hi1(0);
@@ -339,6 +340,7 @@ sum(10000)
 //│     toString() { return "Cont$(" + this.pc + ")"; }
 //│   };
 //│   globalThis.Predef.__stackLimit = 1000;
+//│   globalThis.Predef.__stackOffset = 0;
 //│   globalThis.Predef.__stackDepth = 1;
 //│   globalThis.Predef.__stackHandler = stackHandler;
 //│   res2 = sum3(10000);

hkmc2/shared/src/test/mlscript/handlers/ZCombinator.mls

@@ -91,8 +91,8 @@ let fact =
 :expect 3628800
 :stackSafe 5
 fact(10)
-//│ > 2 993
-//│ > 4 1
+//│ > 2 0
+//│ > 4 0
 //│ > 6 4
 //│ > 8 4
 //│ > 10 8