v8-commands

# V8 Key Commands Use this skill to find the correct commands for common development tasks in V8. This unifies the commands listed in workspace configuration and ensures consistent usage. ## Building V8 uses `gm.py` as a wrapper around GN and Ninja for building. **Mandatory GN Args & Siso Remote Execution Guardrails**: Always include `use_remoteexec = true` in your `args.gn` or via `gm.py` flags to ensure builds utilize remote execution. Remote execution is mandatory in this environment. **Critical Guardrail (Path Strictness)**: The target output directory must sit exactly 2 levels deep relative to the project root (e.g., `out/x64.debug` or `out/x64.release`). - **Build (Debug):** `tools/dev/gm.py quiet x64.debug tests` - **Build (Optimized Debug):** `tools/dev/gm.py quiet x64.optdebug tests` - **Build (Release):** `tools/dev/gm.py quiet x64.release tests` - **Sync DEPS Options:** Use `tools/dev/gm.py quiet x64.optdebug.d8 --sync` to sync DEPS when switching between branches. Use the slower `--sync=force` option if there are still issues with broken DEPS. *Note: Always pass the `quiet` keyword unless told otherwise to avoid excessive output.* ## Debugging Run `d8` with GDB or LLDB for native code debugging. ```bash # Example of running d8 with gdb gdb --args out/x64.debug/d8 --my-flag my-script.js ``` ### Common Diagnostic Flags - `--trace-opt`: Log optimized functions. - `--trace-deopt`: Log when and why functions are deoptimized. - `--trace-gc`: Log garbage collection events. - `--allow-natives-syntax`: Enables calling of internal V8 functions (e.g., `%OptimizeFunctionOnNextCall(f)`) from JavaScript for testing purposes. - `--gdbjit`: Allows seeing Maglev graphs or JavaScript code in GDB backtraces. To debug issues involving code motion disable gdbjit (as it disables code motion). A comprehensive list of all flags can be found by running `out/x64.debug/d8 --help`. ## Testing For detailed instructions on running tests and interpreting failures, see the dedicated test execution guidelines. Key commands summary: - **Run tests:** `tools/run-tests.py --progress dots --outdir=out/x64.optdebug`