[llvm-dev] Debug symbols are missing in elf

[David Blaikie via llvm-dev]

On Wed, Apr 22, 2020 at 9:28 AM Nagaraju Mekala via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> On Tue, Apr 21, 2020 at 6:16 PM Robinson, Paul <paul.robinson at sony.com>
> wrote:
> >
> >
> >
> > > -----Original Message-----
> > > From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Nagaraju
> > > Mekala via llvm-dev
> > > Sent: Tuesday, April 21, 2020 6:04 AM
> > > To: jh7370.2008 at my.bristol.ac.uk
> > > Cc: LLVM Developers Mailing List <llvm-dev at lists.llvm.org>
> > > Subject: Re: [llvm-dev] Debug symbols are missing in elf
> > >
> > > Hi James,
> > >
> > > Thanks for reply.
> > > When I looked in to the generated debug dump from the object file I
> > > found that DW_AT_name is always (indirect string, offset: 0x0): clang
> > > version 8.0.1, instead of variable names.
> >
> > That symptom suggests that relocations from .debug_info to .debug_str
> > are not being handled correctly.  Either your backend is not emitting
> > them correctly, or the dumper does not know what to do with them.
> >
> > If you are able to dump the .rela.debug_info section and it looks
> > reasonable, the fault is most likely with the dumper.  If you are
> > using llvm-dwarfdump then that should not be hard to solve.
> > --paulr
> >
> Hi Paulr,
> Thanks for the reply.
> From your suggestion I have used llvm-dwarfdump and was able to figure
> out that debug_info section was incomplete.
>

What command did you run, on what file, and what was the output?


> Can you please help me in finding which part of the target(Backend
> files) will construct the dwarf data, especially debug_info.
>

LLVM's DWARF generation is implemented in
llvm/lib/CodeGen/AsmPrinter/Dwarf* files


>
> Thanks in Advance,
> Nagaraju
> > >
> > > Below is a sample output of the debug dump.
> > >
> > >  Compilation Unit @ offset 0x0:
> > >    Length:        0x6a (32-bit)
> > >    Version:       4
> > >    Abbrev Offset: 0x0
> > >    Pointer Size:  4
> > >  <0><b>: Abbrev Number: 1 (DW_TAG_compile_unit)
> > >     <c>   DW_AT_producer    : (indirect string, offset: 0x0): clang
> > > version 8.0.1
> > >     <10>   DW_AT_language    : 12       (ANSI C99)
> > >     <12>   DW_AT_name        : (indirect string, offset: 0x0): clang
> > > version 8.0.1
> > >     <16>   DW_AT_stmt_list   : 0x0
> > >     <1a>   DW_AT_comp_dir    : (indirect string, offset: 0x0): clang
> > > version 8.0.1
> > >     <1e>   DW_AT_low_pc      : 0x0
> > >     <22>   DW_AT_high_pc     : 0x6c
> > >  <1><26>: Abbrev Number: 2 (DW_TAG_subprogram)
> > >     <27>   DW_AT_low_pc      : 0x0
> > >     <2b>   DW_AT_high_pc     : 0x6c
> > >     <2f>   DW_AT_frame_base  : 1 byte block: 51         (DW_OP_reg1
> (r1))
> > >     <31>   DW_AT_name        : (indirect string, offset: 0x0): clang
> > > version 8.0.1
> > >     <35>   DW_AT_decl_file   : 1
> > >     <36>   DW_AT_decl_line   : 51
> > >     <37>   DW_AT_type        : <0x66>
> > >     <3b>   DW_AT_external    : 1
> > >
> > > -Nagaraju
> >
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