dawn-cmake/docs/dawn/debugging.md

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# Debugging Dawn
## Toggles
There are various debug-related Toggles that can help diagnose issues. Useful debug toggles:
- `dump_shaders`: Log input WGSL shaders and translated backend shaders (MSL/ HLSL/DXBC/DXIL / SPIR-V).
- `disable_symbol_renaming`: As much as possible, disable renaming of symbols (variables, function names, etc.). This can make dumped shaders more readable.
- `emit_hlsl_debug_symbols`: Sets the D3DCOMPILE_SKIP_OPTIMIZATION and D3DCOMPILE_DEBUG compilation flags when compiling HLSL code.
- `use_user_defined_labels_in_backend`: Forward object labels to the backend so that they can be seen in native debugging tools like RenderDoc, PIX, or Mac Instruments.
Toggles may be enabled/disabled in different ways.
- **In code:**
Use extension struct `DawnTogglesDescriptor` chained on `DeviceDescriptor`.
For example:
```c++
const char* const enabledToggles[] = {"dump_shaders", "disable_symbol_renaming"};
wgpu::DawnTogglesDescriptor deviceTogglesDesc;
deviceTogglesDesc.enabledToggles = enabledToggles;
deviceTogglesDesc.enabledTogglesCount = 2;
wgpu::DeviceDescriptor deviceDescriptor;
deviceDescriptor.nextInChain = &deviceTogglesDesc;
```
- **Command-line for Chrome**
Run Chrome with command line flags`--enable-dawn-features` and/or `--disable-dawn-features` to force enable/disable toggles. Toggles should be comma-delimited.
For example:
`--enable-dawn-features=dump_shaders,disable_symbol_renaming`
- **Command-line for dawn_end2end_tests/dawn_unittests**
Run Dawn test binaries with command line flags`--enable-toggles` and/or `--disable-toggles` to force enable/disable toggles. Toggles should be comma-delimited.
For example:
`dawn_end2end_tests --enable-toggles=dump_shaders,disable_symbol_renaming`
## Environment Variables
- `DAWN_DEBUG_BREAK_ON_ERROR`
Errors in WebGPU are reported asynchronously which may make debugging difficult because at the time an error is reported, you can't easily create a breakpoint to inspect the callstack in your application.
Setting `DAWN_DEBUG_BREAK_ON_ERROR` to a non-empty, non-zero value will execute a debug breakpoint
instruction ([`dawn::Breakpoint()`](https://source.chromium.org/chromium/chromium/src/+/main:third_party/dawn/src/dawn/common/Assert.cpp?q=dawn::Breakpoint)) as soon as any type of error is generated.