[LLVMdev] Advice for setting debug locations

[Keno Fischer]

Oh, I see. Sorry I misunderstood. I'll try to come up with some
minimal IR. The assertion stems from the fact that getCompileUnitDIE()
returns null and then crashes at DWARFUnit.cpp:301. I admit I don't
know if this problem is on the parsing or the generation side.

While I come up with the IR, basically what I was doing was using a
DebugLoc with scope being a DIFile rather than a DISubprogram as
before.

On Wed, Aug 13, 2014 at 7:00 PM, David Blaikie <dblaikie at gmail.com> wrote:
> On Wed, Aug 13, 2014 at 3:47 PM, Keno Fischer
> <kfischer at college.harvard.edu> wrote:
>> Sorry, I didn't have a small IR example and I was sure I was just
>> doing something stupid. Thanks for the help, I'll try it out and
>> report back. Maybe it would be good to add an assertion or something
>> that tells people what's wrong in this case, since the generated DWARF
>> seems to be invalid?
>
> I'm still not sure exactly where things went wrong for you, so unsure
> as to where to add the assertion - a small IR example would be helpful
> for that. The suggestion to use the DW_TAG_lexical_block 3-field-form
> was just based on your description of your goals, it sounded like that
> was the tool you needed & weren't using yet.
>
>>
>> On Wed, Aug 13, 2014 at 5:53 PM, David Blaikie <dblaikie at gmail.com> wrote:
>>> Use the second form of DW_TAG_lexical_block metadata (the one with 3
>>> fields - http://llvm.org/docs/SourceLevelDebugging.html#block-descriptors
>>> ) to describe file changes within a sequence of LLVM IR functions.
>>>
>>> A small example of IR would be easier to follow if you want help
>>> debugging why your IR is causing problems.
>>>
>>> On Wed, Aug 13, 2014 at 2:25 PM, Keno Fischer
>>> <kfischer at college.harvard.edu> wrote:
>>>> Hello,
>>>>
>>>> I'm trying to fix a long standing issue we are having in Julia where
>>>> when the file information switched, we weren't recording that
>>>> correctly, so line information showed up in the wrong file. Basically
>>>> we would always create a scope with the DISubprogram and the given
>>>> line number. What I tried was to change the scope to be a DIFile
>>>> instead so we'd get the correct file information. Unfortunately I had
>>>> to revert this [1], because it crashes llvm's dwarf reader (which we
>>>> use to get line information for backtraces when exceptions are thrown)
>>>> with the following backtrace:
>>>>
>>>> isNULL at /Users/kfischer/Documents/julia-debug/deps/llvm-svn/lib/DebugInfo/DWARFDebugInfoEntry.h:52
>>>> getAddressRanges at
>>>> /Users/kfischer/Documents/julia-debug/deps/llvm-svn/lib/DebugInfo/DWARFDebugInfoEntry.cpp:242
>>>> collectAddressRanges at
>>>> /Users/kfischer/Documents/julia-debug/deps/llvm-svn/lib/DebugInfo/DWARFUnit.cpp:302
>>>> generate at /Users/kfischer/Documents/julia-debug/deps/llvm-svn/lib/DebugInfo/DWARFDebugAranges.cpp:54
>>>> getDebugAranges at
>>>> /Users/kfischer/Documents/julia-debug/deps/llvm-svn/lib/DebugInfo/DWARFContext.cpp:270
>>>> getCompileUnitForAddress at
>>>> /Users/kfischer/Documents/julia-debug/deps/llvm-svn/lib/DebugInfo/DWARFContext.cpp:423
>>>>
>>>> Can somebody tell me what the correct way to achieve this is?
>>>>
>>>> [1] https://github.com/JuliaLang/julia/commit/e494cb6dff193ecb0e254981be0f1122ae294d04
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