vm: properly clear try stack in CALL

Signed-off-by: Evgeniy Stratonikov <evgeniy@nspcc.ru>

pkg/vm/vm.go

@@ -1594,6 +1594,9 @@ func (v *VM) call(ctx *Context, offset int) {
 	newCtx.retCount = -1
 	newCtx.local = nil
 	newCtx.arguments = nil
+	// If memory for `elems` is reused, we can end up
+	// with incorrect exception context state in the caller.
+	newCtx.tryStack.elems = nil
 	initStack(&newCtx.tryStack, "exception", nil)
 	newCtx.NEF = ctx.NEF
 	v.istack.PushItem(newCtx)

pkg/vm/vm_test.go

@@ -1027,6 +1027,22 @@ func TestTRY(t *testing.T) {
 		// add 5 to the exception, mul to the result of inner finally (2)
 		getTRYTestFunc(47, inner, append(add5, byte(opcode.MUL)), add9)(t)
 	})
+	t.Run("nested, in throw and catch in call", func(t *testing.T) {
+		catchP := []byte{byte(opcode.PUSH10), byte(opcode.ADD)}
+		inner := getTRYProgram(throw, catchP, []byte{byte(opcode.PUSH2)})
+		outer := getTRYProgram([]byte{byte(opcode.CALL), 0}, []byte{byte(opcode.PUSH3)}, []byte{byte(opcode.PUSH4)})
+		outer = append(outer, byte(opcode.RET))
+		outer[4] = byte(len(outer) - 3) // CALL argument at 3 (TRY) + 1 (CALL opcode)
+		outer = append(outer, inner...)
+		outer = append(outer, byte(opcode.RET))
+
+		v := load(outer)
+		runVM(t, v)
+		require.Equal(t, 3, v.Estack().Len())
+		require.Equal(t, big.NewInt(4), v.Estack().Pop().Value())  // outer FINALLY
+		require.Equal(t, big.NewInt(2), v.Estack().Pop().Value())  // inner FINALLY
+		require.Equal(t, big.NewInt(23), v.Estack().Pop().Value()) // inner THROW + CATCH
+	})
 }
 
 func TestMEMCPY(t *testing.T) {