godot-debugging-profiling

name

godot-debugging-profiling

description

Expert debugging workflows including print debugging (push_warning, push_error, assert), breakpoints (conditional breakpoints), Godot Debugger (stack trace, variables, remote debug), profiler (time profiler, memory monitor), error handling patterns, and performance optimization. Use for bug fixing, performance tuning, or development diagnostics. Trigger keywords: breakpoint, print_debug, push_error, assert, profiler, remote_debug, memory_leak, orphan_nodes, Performance.get_monitor.

Debugging & Profiling

Expert guidance for finding and fixing bugs efficiently with Godot's debugging tools.

NEVER Do

• NEVER use print() without descriptive context — print(value) is useless. Use print("Player health:", health) with labels.
• NEVER leave debug prints in release builds — Wrap in if OS.is_debug_build() or use custom DEBUG const. Prints slow down release.
• NEVER ignore push_warning() messages — Warnings indicate potential bugs (null refs, deprecated APIs). Fix them before they become errors.
• NEVER use assert() for runtime validation in release — Asserts are disabled in release builds. Use if not condition: push_error() for runtime checks.
• NEVER profile in debug mode — Debug builds are 5-10x slower. Always profile with release exports or --release flag.
• NEVER assume Engine.capture_script_backtraces(true) is cheap — Capturing locals allocates significant memory and can prevent objects from being deallocated, causing artificial leaks [19].
• NEVER call push_error() or print() inside a custom Logger._log_message override — This causes infinite recursion and crashes as the logger intercepts its own output [20].
• NEVER leave the Visual Profiler running during gameplay tests — Continuous polling degrades framerates significantly, invalidating actual performance metrics [21].
• NEVER rely on OS.get_ticks_msec() for microbenchmarking — Milliseconds lack precision for logic timing; ALWAYS use Time.get_ticks_usec() for microsecond precision [22].
• NEVER assume OBJECT_ORPHAN_NODE_COUNT works in production — This monitor is strictly debug-only; it safely returns 0 in release builds, potentially hiding leaks [23].
• NEVER benchmark with V-Sync enabled — V-Sync throttles metrics to the monitor refresh rate, masking the true CPU/GPU processing overhead [24].
• NEVER leave print_stack() or print_debug() in release builds — These are often stripped or useless outside the debugger. Use structured logging for production [25].
• NEVER strip debugging symbols if using external C++ profilers — Stripping destroys call stack readability for external tools like Perfetto or VerySleepy [26].
• NEVER forget to unregister an EditorDebuggerPlugin in _exit_tree() — Failing to clean up leaves "ghost" connections in the engine's debugging loop [27].
• NEVER trust the Visual Profiler on macOS when using the Compatibility renderer — Platform-specific driver limitations severely restrict OpenGL profiling accuracy on macOS [28].

---

Available Scripts

MANDATORY: Read the appropriate script before implementing the corresponding pattern.

high_precision_benchmarker.gd

Micrometer-precision execution timing using Time.get_ticks_usec(), essential for identifying CPU micro-bottlenecks.

orphan_node_detector.gd

Automated detection and logging of "Orphan Nodes" (nodes removed from tree but not freed) using internal Performance monitors.

advanced_backtrace_recorder.gd

Capturing detailed script backtraces programmatically, including local variable snapshots for deep crash reporting.

engine_error_interceptor.gd

Intercepting underlying C++ engine errors and piping them to custom backend logs or analytics services.

custom_editor_monitor.gd

Exposing game-specific performance metrics (AI counts, bullet physics) directly to the Godot Editor's Debugger > Monitors tab.

debugger_tab_plugin.gd

Project-specific debugger extensions that inject custom visual tabs and data into the Godot bottom panel.

thread_safe_logger.gd

Mutext-locked logger subclass for thread-safe writing of logs from worker threads to external files.

custom_debug_draw.gd

Pro-level visualization patterns for non-visual data like pathfinding nodes, physics raycasts, and local AI influence maps.

break_on_condition.gd

Hardcoded breakpoint triggers for halting execution on invalid logic states in a team-agnostic manner.

remote_debug_console.gd

In-game command console for debugging mobile and console builds where standard terminal output is inaccessible.

Do NOT Load debug_overlay.gd in release builds - wrap usage in if OS.is_debug_build().

---

Print Debugging

# Basic print
print("Value: ", some_value)

# Formatted print
print("Player at %s with health %d" % [position, health])

# Print with caller info
print_debug("Debug info here")

# Warning (non-fatal)
push_warning("This might be a problem")

# Error (non-fatal)
push_error("Something went wrong!")

# Assert (fatal in debug)
assert(health > 0, "Health cannot be negative!")

Breakpoints

Set Breakpoint:

• Click line number gutter in script editor
• Or use breakpoint keyword:

func suspicious_function() -> void:
    breakpoint  # Execution stops here
    var result := calculate_something()

Debugger Panel

Debug → Debugger (Ctrl+Shift+D)

Tabs:

• Stack Trace: Call stack when paused
• Variables: Inspect local/member variables
• Breakpoints: Manage all breakpoints
• Errors: Runtime errors and warnings

Remote Debug

Debug running game:

1. Run project (F5)
2. Debug → Remote Debug → Select running instance
3. Inspect live game state

Common Debugging Patterns

Null Reference

# ❌ Crash: null reference
$NonExistentNode.do_thing()

# ✅ Safe: check first
var node := get_node_or_null("MaybeExists")
if node:
    node.do_thing()

Track State Changes

var _health: int = 100

var health: int:
    get:
        return _health
    set(value):
        print("Health changed: %d → %d" % [_health, value])
        print_stack()  # Show who changed it
        _health = value

Visualize Raycasts

func _draw() -> void:
    if Engine.is_editor_hint():
        draw_line(Vector2.ZERO, ray_direction * ray_length, Color.RED, 2.0)

Debug Draw in 3D

# Use DebugDraw addon or create debug meshes
func debug_draw_sphere(pos: Vector3, radius: float) -> void:
    var mesh := SphereMesh.new()
    mesh.radius = radius
    var instance := MeshInstance3D.new()
    instance.mesh = mesh
    instance.global_position = pos
    add_child(instance)

Error Handling

# Handle file errors
func load_save() -> Dictionary:
    if not FileAccess.file_exists(SAVE_PATH):
        push_warning("No save file found")
        return {}
    
    var file := FileAccess.open(SAVE_PATH, FileAccess.READ)
    if file == null:
        push_error("Failed to open save: %s" % FileAccess.get_open_error())
        return {}
    
    var json := JSON.new()
    var error := json.parse(file.get_as_text())
    if error != OK:
        push_error("JSON parse error: %s" % json.get_error_message())
        return {}
    
    return json.data

Profiler

Debug → Profiler (F3)

Time Profiler

• Shows function execution times
• Identify slow functions
• Target: < 16.67ms per frame (60 FPS)

Monitor

• FPS, physics, memory
• Object count
• Draw calls

Common Performance Issues

Issue: Low FPS

# Check in _process
func _process(delta: float) -> void:
    print(Engine.get_frames_per_second())  # Monitor FPS

Issue: Memory Leaks

# Check with print
func _exit_tree() -> void:
    print("Node freed: ", name)

# Use groups to track
add_to_group("tracked")
print("Active objects: ", get_tree().get_nodes_in_group("tracked").size())

Issue: Orphaned Nodes

# Check for orphans
func check_orphans() -> void:
    print("Orphan nodes: ", Performance.get_monitor(Performance.OBJECT_ORPHAN_NODE_COUNT))

Debug Console

# Runtime debug console
var console_visible := false

func _input(event: InputEvent) -> void:
    if event is InputEventKey and event.keycode == KEY_QUOTELEFT:
        console_visible = not console_visible
        $DebugConsole.visible = console_visible

Best Practices

1. Use Debug Flags

const DEBUG := true

func debug_log(message: String) -> void:
    if DEBUG:
        print("[DEBUG] ", message)

2. Conditional Breakpoints

# Only break on specific condition
if player.health <= 0:
    breakpoint

3. Scene Tree Inspector

Debug → Remote Debug → Inspect scene tree
See live node hierarchy

Expert Debugging Patterns

1. Automated-QA-Suite (Headless CI/CD)

Pattern for verifying game state in automated pipelines with deterministic exit codes.

• Headless Execution: Use godot --headless -s test_runner.gd to run tests without a display server.
• Verification: Evaluate state and call get_tree().quit(0) for success or quit(1) for failure to pass exit codes back to the CI runner.
• Implementation:

  func _run() -> void: # Main entry for --script
      var success := _run_all_tests()
      if success:
          print("[TEST_RESULT] PASS")
          get_tree().quit(0)
      else:
          printerr("[TEST_RESULT] FAIL")
          get_tree().quit(1)
  

• CLI Flags: Use --gpu-validation and --gpu-abort to catch driver-level errors in CI.

2. Visual-Profiler-Extensions (GPU Costs)

Custom diagnostic overlays to monitor rendering overhead in-game.

• Metric Querying: Use RenderingServer.get_rendering_info(RenderingServer.RENDERING_INFO_TOTAL_DRAW_CALLS_IN_FRAME) for draw calls.
• GPU Profiling: Enable debug/settings/stdout/print_gpu_profile in Project Settings to dump a per-second breakdown of CanvasItem, shadow, and glow costs.
• VRAM Tracking: Use Performance.get_monitor(Performance.RENDER_VIDEO_MEM_USED) to track total GPU memory consumption.
• Implementation:

  func _process(_delta):
      var calls = RenderingServer.get_rendering_info(RenderingServer.RENDERING_INFO_TOTAL_DRAW_CALLS_IN_FRAME)
      var primitives = RenderingServer.get_rendering_info(RenderingServer.RENDERING_INFO_TOTAL_PRIMITIVES_IN_FRAME)
      # Display on-screen overlay
  

3. Thread-Safety-Analyzer (Race Conditions)

Ensuring safe access to the SceneTree and data from worker threads.

• Safety Checks: Use Thread.set_thread_safety_checks_enabled(true) to force Godot to throw errors when unsafe SceneTree access occurs from a thread.
• Deferred Access: ALWAYS use call_deferred() or set_deferred() when a worker thread needs to modify the SceneTree.
• Server Safety: Servers (Rendering/Physics) are thread-safe ONLY if enabled in Project Settings under threading/worker_pool/allow_group_tasks.
• Implementation:

  func _ready():
      Thread.set_thread_safety_checks_enabled(true) # Global enforcement
  

4. Memory-Leak-Tracker (Transient Scenes)

Identifying leaks in scenes that are instantiated and freed frequently.

• Orphan Detection: Periodically check Node.get_orphan_node_ids(). If the count grows indefinitely after closing transient scenes, you have a leak.
• ObjectDB Snapshots: Use the Godot 4.6 ObjectDB Profiler to take "Before" and "After" snapshots. Diffing these reveals exactly which RefCounted objects are causing circular reference leaks.

Reference

• Godot Docs: Debugger

Related

• Master Skill: godot-master