Sam Collinson5d ago
Ole Begemann

I didn’t know binaries could embed LLDB-specific bytecode for formatting custom data types nicely in the debugger, as shown in this swift-collections PR: https://github.com/apple/swift-collections/pull/607. The code also uses fancy new Swift features to place the bytecode in a specific linker section:

@⁠section(".lldbformatters")
@⁠used
let __BasicContainers___RigidArray______formatter: (UInt8, UInt8, …, UInt8) = …

Mar 19 at 9:23amWeb
Show threadGeoff Foster6d ago
@ole It looks like this is what the @DebugDescription macro ends up adding, which is pretty neat when I can get it to work correctly...
Show threadOle Begemann6d ago
@gfoster I had forgotten about @⁠DebugDescription, thanks a lot for calling it out! In my quick test, it looks like @⁠DebugDescription emits a @⁠section(".lldbsummaries"), which contains a sort of format string. So it’s subtly different than the @⁠section(".lldbformatters") generated by the PR I linked to, which is presumably more flexible as it contains actual code the debugger executes. But most types probably don’t need that flexibility.