RustRover 2023.3 Help

Examine suspended program

After the debugger session has started, the Debug tool window will appear, and the program will run normally until a breakpoint is hit or you pause the program manually.

After that, the program is suspended, allowing you to examine its current state, control its further execution, and test various scenarios at runtime.

Frames and threads

The state of the program is represented by frames. When the program is suspended, the current frame stack is displayed in the Frames pane located on the Threads & Variables tab.

Frames pane

A frame corresponds to the active method or function call. It stores the local variables of the called method or function, its arguments, and the code context that enables expression evaluation.

Each time a method is called, a new frame is added to the top of the stack. When the execution of a method is complete, the corresponding frame is removed from the stack (in the last in, first out fashion).

Examining frames helps you understand why particular parameters were passed to a method and what the state of the caller was at the time of calling.

Threads

You can navigate through the list of the application threads. The ID given by the OS on thread start can help you identify the thread you are interested in:

Thread switcher

Thread Icons

Icons near each thread indicate the status of the thread relative to the current debugging session.

Icon

Description

Current thread

The current thread in suspended state.

Running thread

An active thread.

Thread at breakpoint

The thread that has hit the current breakpoint.

Suspended thread

A suspended thread. Threads are marked as suspended when they were paused by the debugger.

Frozen thread

A frozen thread. Threads are marked as frozen when they were manually paused.

Copy stack to clipboard

  • To copy the call stack for the current thread, right-click anywhere on the Frames pane and select Copy Stack.

Explore and edit variables

The Variables pane shows the list of the variables in the selected frame/thread. Examining the variables can help you understand why the program operates in a certain way.

Variables pane

Compare variables with clipboard

When you need to compare a variable value with some other value, use the Compare Value with Clipboard option. This is helpful, for example, when a variable holds a long string, and you need to compare it with another long string.

  1. Copy the content you want to compare (for example, from a text file).

  2. In the Variables pane, right-click the variable that you want to compare with and select Compare Value with Clipboard.

  3. Examine the differences in the Diff Viewer that opens.

View variables in a dedicated dialog

RustRover allows you to inspect variables in a dedicated dialog. This is useful when you need to keep track of some variable (or the object whose reference it holds) and at the same time be able to navigate between frames and threads.

  • Right-click a variable or a watch and select Inspect.

    Inspect dialog

Set variable values

If you want to test how the program would behave in certain conditions or fix its current behavior at runtime, you can do that by setting/changing the variable values.

  1. Select a variable and press F2. Alternatively, select Set Value from the context menu.

  2. Enter the value for the variable and press Enter.

    Enter new value for the variable in the field right next to its name

If you need to look into the source code where some variable or type is declared, you can move there right from the Variables pane.

  • To navigate to the code where the variable is declared, right-click the variable and select Jump to Source F4.

  • To navigate to the type declaration of the variable type, right-click the variable and select Jump to Type Source Shift+F4.

Evaluate expressions

RustRover lets you evaluate expressions during a debugging session to obtain additional details about the program state or test various scenarios at runtime.

Evaluate a simple expression in the editor

To quickly evaluate an expression, point at it in the editor. Note that method calls cannot be evaluated this way.

  1. Point at the expression you want to evaluate. The result of the expression appears in a tooltip.

    Value tooltip
  2. To view child elements , click the Expand button or press Ctrl+F1.

    Resulting objects are represented by trees. This helps you view their internal state

If you find value tooltips distracting, you can increase the delay or disable them altogether. To do this, in the Settings dialog (Ctrl+Alt+S) , go to Build, Execution, Deployment | Debugger | Data Views and set the Show value tooltip and Value tooltip delay options as required.

Evaluate a complex expression in the editor

If you want to evaluate an expression in the code that involves a method call, or you want to be specific about which portion of expression to evaluate, use the Quick Evaluate Expression option.

  1. Place the caret at the expression (to evaluate the closest matching expression) or select a portion of it (if you want to be specific about which part of a complex expression to evaluate).

  2. Click Run | Debugging Actions | Quick Evaluate Expression Ctrl+Alt+F8. Alternatively, hold Alt and click the selection.

You can configure Quick Evaluate to work for a piece of code on just selecting it (without using the menu/shortcut). Use this option carefully, as you can accidentally call methods when it is enabled.

To configure Quick Evaluate on code selection, go to Settings | Build, Execution, Deployment | Debugger | Data Views and set the Show value tooltip on code selection option as preferred.

Evaluate arbitrary expressions

Evaluating arbitrary expressions is the most flexible evaluating option. It lets you evaluate any code as long as it is in the context of the current frame. Using it, you can evaluate declarations, method calls, loops, and so on.

Use this feature to get additional information about the current state of the program and test various scenarios all within the same debugging session. This saves a lot of time by reducing the number of sessions you have to run.

  1. To evaluate an arbitrary expression, enter it in the Evaluate expression field in the Variables pane and press Enter

    Expression in the Variables pane
  2. The result is displayed right below. You can also add the expression to watches by clicking in the right-hand part of the expression field.

    Add to watches

If you want to evaluate long code blocks, you may want to use a dedicated dialog for that:

Evaluate expressions in a dedicated dialog

  1. If you want to start with some expression or a variable, which is currently in front of you (for example, in the editor or on the Variables pane), select it.

  2. Click Run | Debugging Actions | Evaluate Expression Alt+F8. The shortcut may not work on Ubuntu (for correct operation, adjust the shortcut configuration).

  3. In the Evaluate dialog, modify the selected expression or enter a new one in the Expression field. Click Expand Shift+Enter to modify a multiline code fragment.

    The expression is entered in the Code Fragment field
  4. Click Evaluate (Ctrl+Enter for multiline mode). The expression result appears in the Result field.

    The result of the expression is taken from the return statement. When there is no return statement, the result is taken from the last line of code (it does not even have to be an expression: a single literal works too). When there is no valid line to take the value from, the result is undefined. If the specified expression cannot be evaluated, the Result field indicates the reason.

The Evaluate dialog is non-modal, so you can switch the focus back to the editor to copy other variables and expressions. You can also open multiple Evaluate dialogs if necessary.

View values inline

RustRover shows the values of the variables right next to their usage.

Variable values are displayed at the lines where they are used

Once the variable value has changed, the inline view is updated with the new value and changes its color.

Inline values of the variables change with each step

If a line contains a reference to an object, you can examine its fields right in the editor. From this popup, you can also change the variable values and add inline watches.

Inline debugger hints

The inline view is enabled by default. To turn it off, in the Settings dialog (Ctrl+Alt+S) , go to Build, Execution, Deployment | Debugger | Data Views and disable the Show values inline option.

Add an Inline Watch

If you want the result of some expression to appear on a particular line, you can set up an inline watch for that. Inline watches are persistent and remain active after session restart.

  1. Click the inline hint referring to the object whose field you want to track.

  2. In the popup, select the field and click Add as Inline Watch.

    Adding an inline watch
  3. Fine-tune the watch if needed. You can use any valid expression as a watch.

To remove an inline watch, locate it in the Variables pane, right-click, and select Remove Watch:

Remove an inline watch

Watches

If you want to keep track of some variable or the result of a more complex expression, set up a watch for this variable or expression. This is useful when you need to evaluate something that is not regularly displayed on the list of variables, or to pin some instance variable thus eliminating the need to expand the tree after each step.

Watches are evaluated in the context of the selected frame. Watches cannot be evaluated when they are out of context or when they fail to compile. If this is the case, the watch is marked with the error icon Error icon.

By default, watches are shown together with variables in the Variables pane. To hide/reveal the Watches pane, use the Separate watches option in the Layout Settings Layout options button menu.

Add a watch

  • Enter the expression in the top part of the Variables pane, then click Add to Watches.

    Add to watches

After you have added a variable/expression to Watches, it stays there and is evaluated for each step, providing you with the result in the current context.

Edit a watch

  • Right-click the desired watch and select Edit.

Copy a watch

  1. Select the watch you want to copy.

  2. Click Duplicate Watch Duplicate Watch button on the Variables pane or press Ctrl+D.

Delete a watch

  • To remove a single watch, right-click it and select Remove Watch. Alternatively, select the watch and press Delete.

    Remove an inline watch
  • To remove all watches, right-click anywhere on the Variables/ Watches pane and select Remove All Watches.

Watches allow for the same actions as variables do. For example, you can view them in a dedicated dialog or use them to navigate to the source code.

Watches are a part of your project. This means you can stop and rerun the debugging session without risk of losing them.

Execution point

Return to the current execution point

Examining the program state involves navigating in code, and you often need to return to the place where your program is suspended.

Do one of the following:

  • In the main menu, go to Run | Debugging Actions | Show Execution Point.

  • Press Alt+F10.

  • Click The More button on the stepping toolbar of the Debug tool window, then select the The Show Execution Point button Show Execution Point option from the list.

The current execution point is indicated with a blue line. The code at this line has not been executed yet.

Blue line indicating the current execution point

Set execution point

The Set Execution Point action allows you to jump to an arbitrary line of code in the editor (both forward and backward) during a debug session and set the execution point there, skipping all the other commands in between.

Set execution point

Use one of the following options:

  • Drag the current execution pointer (the orange arrow in the gutter) to the required line of code.

    Execution pointer in the gutter
  • Place the caret at the required line and call Set Execution Point to Cursor from Help | Find Action (Ctrl+Shift+A).

    Set Execution Point in Search Everywhere dialog
  • In Settings | Keymap, assign a shortcut for the Set Execution Point to Cursor action.

    Assigning a shortcut to Set Execution Point

    Save the settings, place the caret at the required line, and use the shortcut.

Last modified: 20 February 2024