[llvm-dev] DebugInfo proposal: Emit an explicit empty address range on CUs with no code addresses

[via llvm-dev]

Seems reasonable to me.
--paulr

From: David Blaikie [mailto:dblaikie at gmail.com]
Sent: Monday, December 17, 2018 3:35 AM
To: Adrian Prantl
Cc: llvm-dev; Jonas Devlieghere; Robinson, Paul; Eric Christopher
Subject: Re: DebugInfo proposal: Emit an explicit empty address range on CUs with no code addresses

Looks like I argued (& then tested) previously for support for the case where the CU has no ranges, but sub-DIEs do: http://lists.llvm.org/pipermail/llvm-dev/2017-November/119131.html

(Just for the record, LLVM gained support for CU ranges were implemented r197776, December 2013 (& shortly after that became the default in r203968, March 2014 - in the 3.5 release) - looks like GCC got this somewhere between GCC 4.1 and GCC 4.4 according to godbolt testing, so on/before March 2012 I think)


So I've gone ahead and committed this change in r349333 - open to further discussion, reverting it, etc.

- Dave

On Wed, Nov 28, 2018 at 10:48 AM David Blaikie <dblaikie at gmail.com<mailto:dblaikie at gmail.com>> wrote:
Yeah, fair - I'll give it a week or something, see if Paul or anyone else has ideas about why the existing behavior might be useful before I remove it.

On Wed, Nov 28, 2018 at 10:27 AM Adrian Prantl <aprantl at apple.com<mailto:aprantl at apple.com>> wrote:


On Nov 28, 2018, at 9:50 AM, David Blaikie <dblaikie at gmail.com<mailto:dblaikie at gmail.com>> wrote:


> a) decide that a unit without ranges covers no ranges - and don't do the search

Are there compilers that do this ("forget" to emit ranges) that we care to support with llvm-symbolizer?

I'm not specifically aware of any, though haven't gone looking.

Just in case this wasn't obvious in the sub-text:
I think we should figure out whether this assumption in llvm-symbolizer is actually needed to support a compiler we care about and then potentially remove it, or enforce it only when the CU is < DWARF 5 or something like that.

-- adrian
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