Version: 1.1.0

Debugging

Mojo programs debug with prints, assertions, and the LLDB-based mojo debug flow.

Essentials

• print of intermediate values is still the fastest first step.
• comptime assert catches mistakes before a binary exists.
• mojo debug file.mojo launches the debugger.
• The VS Code extension can drive the same debugger.
• Optimize after the values are right. Inlined kernels are harder to step through.

Example

$ mojo debug hello.mojo

Keep in mind

When a GPU kernel misbehaves, first run the same math on the CPU. Most index bugs show up there.