DWARF support

[Ben Gamari]

Richard Eisenberg <lists at richarde.dev> writes:

> Thanks for this!
>
>> On Nov 17, 2021, at 7:27 AM, Moritz Angermann <moritz.angermann at gmail.com> wrote:
>> 
>> For Linux and most BSDs, we have settled on the Executable and Linking Format (ELF) as the container format for
>> your machine code.  And you might see where the inspiration for DWARF might come from.
>
> This suggests to me that DWARF is the canonical format for debugging information on Linux and most BSDs. Is that statement correct? If so, how is that different to "platform-native"? Actually, the precise wording doesn't matter: I think I'm just requesting for a more direct relationship between "DWARF" and "compatibility with all the debugging and profiling tools you use for other languages".
>
>> 
>> For macOS, we have mach object (mach-o) as the container format. Its distinctly different to ELF, and also the
>> reason why Linux/BSD and macOS are sometimes substantially different, wrt to executable packaging and linking.
>
> OK. So there is no macOS support here. That's fine -- I'm just trying to understand the status quo.
>
>> 
>> For windows we have Portable Executable (PE) as the container format.
>
> This implies that the DWARF work is (unsurprisingly) completely inapplicable for Windows.
>
>> Depending on how familiar you are with development on macOS, you might know the notion of dSYM folders,
>> where macOS usually separate the application binary into the binary, and then stores the (d)ebug (SYM)bols in
>> a separate folder. Those are iirc DWARF objects in the end.
>
> This suggests to me that the DWARF work is applicable to the macOS use case, but much more work still needs to be done. OK.
>
> Looking for more information, I checked the manual. And I found this:
> https://downloads.haskell.org/ghc/latest/docs/html/users_guide/debug-info.html
> It's really helpful! And it suggests that I actually *can* do this on
> macOS. Perhaps that video will really happen after all.
>
I should clarify here that there are really two pieces to "debug
information support":

 * the code generation logic responsible for producing the DWARF
   metadata

 * the RTS support for using that information to unwind the stack at
   runtime

That section really describes the former. As noted in my earlier email
and in #20702, the library used by the RTS to implement unwinding only
targets ELF platforms.

Cheers,

- Ben

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 487 bytes
Desc: not available
URL: <http://mail.haskell.org/pipermail/ghc-devs/attachments/20211118/7a039d87/attachment.sig>