[LLVMdev] Debug Info Documentation State

[Eric Christopher]

Understood. Getting some bindings for your language might be an easier way
of keeping up to date. The C API is reliable, C++/IR format not so much.
Quite a bit has already changed since 3.2.

-eric


On Wed, Mar 20, 2013 at 3:51 PM, Erkki Lindpere <villane at gmail.com> wrote:

> Thanks for the quick reply! I will keep the DIBuilder and Clang's
> CGDebugInfo as my reference for now.
>
> At the moment I want to stick with generating .ll -- it's somewhat easier
> for me to debug the output of my compiler that way, and I haven't
> programmed much in C/C++ for years -- mostly been a JVM guy. But at one
> point I may want to look into bindings or even creating a bootstrapped
> compiler.
>
>
> On Wed, Mar 20, 2013 at 11:33 PM, Eric Christopher <echristo at gmail.com>wrote:
>
>>
>>
>>
>> On Wed, Mar 20, 2013 at 2:21 PM, Erkki Lindpere <villane at gmail.com>wrote:
>>
>>> Hi,
>>>
>>> I wanted to add debug info to my language (compiler written in Scala,
>>> outputs .ll files), but I found it really hard to do based on the
>>> documentation provided at http://llvm.org/docs/SourceLevelDebugging.html(I looked at the specific doc for LLVM 3.0 though)
>>>
>>> With LLVM 3.0, DI version 8 (which is documented there) seemed to work,
>>> except DW_TAG_auto_variable for which I used version tag 11 and imitated
>>> what clang was doing.
>>>
>>> Got that working for simple programs, but now I switched to LLVM 3.2 and
>>> that debug info doesn't work any more. My best bet seems to be looking at
>>> how Clang/LLVM does it internally.
>>>
>>> PS. For anyone else looking for this, lib/VMCore/DIBuilder.cpp seems to
>>> be the best place to look what the structures should look like.
>>>
>>>
>> Yes. You should use DIBuilder if at all possible or construct something
>> that does the same thing if you need bindings. But I'd probably just do
>> bindings, producing the text is the least portable way.
>>
>>
>>> My question is, any plans to updating the documentation? Documenting
>>> different versions of the debug info is probably too much, but the docs
>>> should at least be of a working version (of course it's possible that
>>> Version 8 works fine and I was just doing something wrong).
>>>
>>
>> We've removed the versioning on debug info recently and it will continue
>> to be an unstable format for the foreseeable future. Updating the
>> documentation is definitely possible, and should be happening as we move
>> around fields and change things. It's possible it hasn't happened of late
>> and so that should probably be fixed. A good chunk of the layout still
>> looks correct - but will be incorrect against any released version even if
>> it was updated. It should reflect top of tree.
>>
>> That said, looking at how clang emits debug information is guaranteed to
>> be the current correct way to emit it so that what you emit is understood
>> by the backend and if you've got any specific questions the mailing list
>> should work well.
>>
>> -eric
>>
>>
>>
>
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