[LLVMdev] Advice for setting debug locations

[Keno Fischer]

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?

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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