[lld] [llvm] [dyndbg][LLD][ELF] Prototype LLD support for dynamic debugging (PR #190939)

[Andrew Ng via llvm-commits]

nga888 wrote:

@smithp35, thanks for the fast response.

>     * `LLVM_ELF` is a very general name. If this is to be specific to embedding a relocatable ELF file, perhaps something like `LLVM_EMBEDDED_ELF`.

Yes, my intention was to make it general. I did initially use `LLVM_EMBEDDED_ELF`, but because it's a section type, I removed the `EMBEDDED`  because it's kind of implied by its "nature" and use. But I'm happy to change it back if this name is preferred.

>     * Is the type intended to represent a family of Embedded ELF use cases, or just this one? If it is just this one then we probably don't need to check the name and rely on the type alone.

Because the section type is intended to be for general use, I've maintained the section name for the "purpose".

>     * Although not necessary for a draft, will need documenting in the LLVM extensions https://llvm.org/docs/Extensions.html

Thanks for pointing out this specific requirement. Because this is draft and still under consideration, I haven't gone to the extent of adding any binutils and other testing requirements for this new section type either. We're also considering making use of the `SHF_OS_NONCONFORMING` section flag for the `.debug_llvm_dyndbg` section. However, this flag is currently not supported by `llvm-objcopy`, so I can't yet include it in this patch. If we decide to go with these changes to the `.debug_llvm_dyndbg` section, then the related dynamic debugging compiler patches will need to adopt them.

https://github.com/llvm/llvm-project/pull/190939