Re: dwarflint: ranges in .debug_loc vs. PCc claimed for containing DIE

[Petr Machata <pmachata at redhat dot com>]

06.10.2009 22:47, Roland McGrath wrote:
> error: .debug_info: DIE 0x13c1: attribute `location': PC range [0x4014a6, 0x401561) outside containing scope
> error: .debug_info: DIE 0x13bc: in this context: [4013d4, 40155a), [4018c0, 4018cf), [401db6, 401e03)
>
> Except please make all the address-value outputs consistent as to whether
> you use 0x or not.

Thanks, re-phrased and made the code use range formatting function.

>> So that all looks genuine--the ranges cited by dwarflint are all there
>> and they really do run off of the PC space of DIE 13bc.  I don't see how
>> to explain this other than by error of toolchain--if a variable is
>> inside a lexical_block, it's range of validity should not leak out of
>> that scope.
>
> Agreed.  It is probably helpful in guessing the nature of the compiler bug
> to cite what's obvious about the actual code at those ranges.  e.g. I'm
> thinking [401561, 4014a61) could be the epilogue that immediately follows
> the inlined_subroutine code, or something like that.

I cut the source down to a trivial reproducer, and the range claims a 
nop used for alignment mid-block.

> If this is with the F-11 or F-12 gcc, then file a Fedora bug against gcc
> with a preprocessed .i file and full invocation details to reproduce the
> bad output.  (This starts with picking a representative case and then
> narrowing/verifying with dwarflint and/or eyeball on that .o file alone.)

That was F-11 gcc.  I built gcc 4.4.1-19, which should end up in F-12. 
That has VTA back-ported and does not reproduce the bug.  I wonder 
whether to report the bug when the new version fixes it anyway.

> Regardless, I would very much like us to collect on the wiki a table of
> known issues indexed by DW_AT_producer pattern, with pointers to the Fedora
> gcc bugzilla reports

Added it among SuspiciousDebuginfoCases.  It's the first reasonably 
documented case on that site, with reproducer and dumps.

Thanks,
PM