[LLVMdev] Inline Symbolication with -gsplit-dwarf

[David Blaikie]

On Wed, Nov 5, 2014 at 6:54 PM, Alexey Samsonov <vonosmas at gmail.com> wrote:

> Hi,
>
> On Tue, Nov 4, 2014 at 4:32 PM, David Blaikie <dblaikie at gmail.com> wrote:
>
>> So, after many shenanigans, we finally have -gmlt-like inline summary
>> debug info in .debug_info when using -gsplit-dwarf (see r221306). Hooray \o/
>>
>> Testing this with asan, it seems to be working:
>>
>> Given a simple example of inlining failure:
>> $ cat asan.cpp
>> __attribute__((always_inline)) inline void func(int* i) { *i = 3; }
>>
>> int main() {
>>   func(nullptr);
>> }
>>
>> The failures before this change:
>>
>>     #0 0x4a320e in func(int*) /tmp/dbginfo/asan.cpp:1:59
>>     #1 0x4a320e in main /tmp/dbginfo/asan.cpp:4
>>
>> And then if we delete the .dwo (to simulate running on another machine,
>> etc, etc):
>>
>>     #0 0x4a320e in main /tmp/dbginfo/asan.cpp:1:59
>>
>> So we get the expected weird mixed stack frame.
>>
>> Then, with the improvements, we see:
>>
>>     #0 0x4a320e in func /tmp/dbginfo/asan.cpp:1:59
>>     #1 0x4a320e in main /tmp/dbginfo/asan.cpp:4
>>
>> One minor quality issue: If we leave the .dwo file in, we still get this
>> last output (the symbolizer is favoring the data in the .o file, by the
>> looks of it, rather than the .dwo file) rather than the extra detail of the
>> function's parameter types, etc.
>>
>> Just thought I'd mention it in case that's a thing you'd like to see
>> fixed/worry about.
>>
>
> Thanks, great to see this coming!
>

Sorry it took a while ;)


> That is, the contents of .dwo file is a strict superset of the debug info
> in executable,
>

This is certainly correct (.dwo is a strict superset of .o data)


> and we should prefer to fetch function names from DIEs in .dwo to fetching
> trimmed names from DIEs in executable?
>

This I believe is the correct direction - as it seems we gain more fidelity
(function type/parameters etc) from the extra data in the .dwo DIEs.


> I think we should fix that (I can work on that once you verify my
> statement).
>

Cool cool - happy to chat over lunch or something, but sounds like we're on
the same page.


>
> --
> Alexey Samsonov
> vonosmas at gmail.com
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20141105/3e533af8/attachment.html>