Clang Time Tracer is a visualizer for Clang's -ftime-trace data. It allows C++ developers to profile their builds and identify which headers or functions are slowing down compilation.
Features
Build & Analyze: Automatically injects -ftime-trace into your compiler arguments and launches the visualization for the current file.
Canvas Renderer: A custom 2D Canvas engine designed to handle large trace files with smooth zooming and panning.
How it works
The extension leverages the -ftime-trace flag (available in Clang 9+ and clang-cl). When triggered, it:
Locates the compilation command for the active file.
Executes the compiler with the tracing flag enabled.
Parses the resulting JSON trace and generates an interactive timeline within a VS Code Webview.
Requirements
Compilation Database: A compile_commands.json file is required in your workspace (usually generated by CMake, Bear, or Meson).
Clang Compatibility: Your compile_commands.json must use clang or clang-cl as the compiler.
Extension Settings
This extension contributes the following settings:
clangTimeTracer.compileCommands.path: The relative path to the folder containing your compile_commands.json. Defaults to the build folder.
Usage & Troubleshooting
Open a C++ source file (.cpp, .cxx, .cc, etc.).
Run the command: Clang Time Tracer: Build and Analyze.
Use the Mouse Wheel to zoom and Click & Drag to pan.
Important Note on Build Systems
Since this extension executes the compiler command directly from compile_commands.json without invoking your full build system (CMake, Bazel, Meson, etc.), you may need to manually run a build once before analyzing. This ensures that any dynamically generated elements—such as generated headers, Protobuf files, or Precompiled Headers (PCH)—are available for the compiler.
