[llvm-dev] Debug Locations for Optimized Code

[Robinson, Paul via llvm-dev]

If the sanitizers already rely on the debug info line table, which
already has a file table, why can't frame layout descriptions use
that as well?

the frame layout descriptions contain names of the local variables, which are not part of line tables.

Sorry, I was not clear, but I was actually responding to this statement:

> Frame layout
> descriptions encode line numbers for local variable declarations. They
> don't include file names to keep object size under control, and we
> can't really afford to add more duplicate debug info.

This suggests that omitting file info from frame layout descriptions is a problem.  But surely whoever is reading the descriptions can get file info from the line table, so there is no need to duplicate that info—in short, why is this a problem in frame layouts?

I assume you build your own frame layout descriptions because you want to work with –gmlt info instead of requiring full –g info?  If you have full –g then the variable info is in the .debug_info section already.
--paulr

From: Kostya Serebryany [mailto:kcc at google.com]
Sent: Thursday, December 08, 2016 9:35 AM
To: Robinson, Paul
Cc: Evgenii Stepanov; llvm-dev at lists.llvm.org
Subject: Re: [llvm-dev] Debug Locations for Optimized Code



On Wed, Dec 7, 2016 at 5:49 PM, Robinson, Paul <paul.robinson at sony.com<mailto:paul.robinson at sony.com>> wrote:


> -----Original Message-----
> From: Evgenii Stepanov [mailto:eugeni.stepanov at gmail.com<mailto:eugeni.stepanov at gmail.com>]
> Sent: Wednesday, December 07, 2016 4:51 PM
> To: Kostya Serebryany
> Cc: Robinson, Paul; llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>
> Subject: Re: [llvm-dev] Debug Locations for Optimized Code
>
> In fact, we are already using "parallel" debug info. Frame layout
> descriptions encode line numbers for local variable declarations. They
> don't include file names to keep object size under control, and we
> can't really afford to add more duplicate debug info.
>
> On Wed, Dec 7, 2016 at 1:44 PM, Kostya Serebryany via llvm-dev
> <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
> > my 2c.
> >
> > the sanitizers rely on debug info to produce human-readable error
> messages,

If the sanitizers already rely on the debug info line table, which
already has a file table, why can't frame layout descriptions use
that as well?

the frame layout descriptions contain names of the local variables, which are not part of line tables.


--paulr

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