Merge branch 'master' into fix/vm-jump-offset

Signed-off-by: Anton Medvedev <anton@medv.io>

Author: antonmedv

vm/vm.go

@@ -625,10 +625,16 @@ func (vm *VM) push(value any) {
 }
 
 func (vm *VM) current() any {
+	if len(vm.Stack) == 0 {
+		panic("stack underflow")
+	}
 	return vm.Stack[len(vm.Stack)-1]
 }
 
 func (vm *VM) pop() any {
+	if len(vm.Stack) == 0 {
+		panic("stack underflow")
+	}
 	value := vm.Stack[len(vm.Stack)-1]
 	vm.Stack = vm.Stack[:len(vm.Stack)-1]
 	return value

vm/vm_test.go

@@ -1429,3 +1429,53 @@ func TestVM_OpJump_NegativeOffset(t *testing.T) {
 	require.Error(t, err)
 	require.Contains(t, err.Error(), "negative jump offset is invalid")
 }
+
+func TestVM_StackUnderflow(t *testing.T) {
+	tests := []struct {
+		name        string
+		bytecode    []vm.Opcode
+		args        []int
+		expectError string
+	}{
+		{
+			name:     "pop after push",
+			bytecode: []vm.Opcode{vm.OpInt, vm.OpPop},
+			args:     []int{42, 0},
+		},
+		{
+			name:        "underflow after valid operations",
+			bytecode:    []vm.Opcode{vm.OpInt, vm.OpInt, vm.OpPop, vm.OpPop, vm.OpPop},
+			args:        []int{1, 2, 0, 0, 0},
+			expectError: "stack underflow",
+		},
+		{
+			name:        "pop on empty stack",
+			bytecode:    []vm.Opcode{vm.OpPop},
+			args:        []int{0},
+			expectError: "stack underflow",
+		},
+		{
+			name:     "pop after push",
+			bytecode: []vm.Opcode{vm.OpInt, vm.OpPop},
+			args:     []int{123, 0},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			program := &vm.Program{
+				Bytecode:  tt.bytecode,
+				Arguments: tt.args,
+				Constants: []any{},
+			}
+
+			_, err := vm.Run(program, nil)
+			if tt.expectError != "" {
+				require.Error(t, err)
+				require.Contains(t, err.Error(), tt.expectError)
+			} else {
+				require.NoError(t, err)
+			}
+		})
+	}
+}