[lldb-dev] reply: reply： lldb debug jit-compiled code with llvm on windows

[Tamas Berghammer via lldb-dev]

On Mon, Nov 30, 2015 at 10:18 AM haifeng_q <haifeng_q at foxmail.com> wrote:

> Question 1:
> On the windows, I use the code implements a function (see
> debug_target.cpp) of JIT (see debug_target_process.cpp), but when
> generating debug information, no production .symtab section for information
> that leads LLDB get JIT debugging information .symtab failure , and then
> set a breakpoint to fail.
>  LLDB command: lldb_result.txt
>  JIT compilation results: debug_target.ll
>
>  Question 2:
>  How JIT debugging supported on Linux?
>

I theory when a new function is JIT-ed then __jit_debug_register_code
function is called where LLDB have a breakpoint set. When that breakpoint
is hit then LLDB reads the JIT-ed elf file based on the information in
__it_debug_descriptor
and processes all debug info in it.

In practice when I last tried JIT debugging with lldb and lli (few weeks
ago) it get the notification for the new JIT-ed elf file but it processed
only the eh_frame from it even though symtab and full debug info was also
provided. Most likely there is some issue around the JIT breakpoint
handling or around the elf file parsing code in LLDB what needs
some investigation.

>
> thanks!
>
> ------------------ The original message ------------------
> *From:* "Zachary Turner";<zturner at google.com>;
> *Data:* 2015年11月21日 AM 0:10
> *Receive:* "Tamas Berghammer"<tberghammer at google.com>; " "<
> haifeng_q at foxmail.com>; "lldb-dev"<lldb-dev at lists.llvm.org>;
> *Title:* Re: [lldb-dev] reply： lldb debug jit-compiled code with llvm on
> windows
>
> Can you also try clang-cl and see if it works?
>
> On Fri, Nov 20, 2015 at 3:02 AM Tamas Berghammer via lldb-dev <
> lldb-dev at lists.llvm.org> wrote:
>
>> I don't know how JIT debugging should work on WIndows with MSVC but I
>> don't think LLDB support it in any way. What I wrote should be true on
>> Linux (and on some related) systems. You might be able to get the same
>> results on Windows if you use lli (LLVM based JIT runner) but I have no
>> knowledge if it will work or not.
>>
>> On Fri, Nov 20, 2015 at 8:56 AM haifeng_q <haifeng_q at foxmail.com> wrote:
>>
>>> My analysis of the code, the reasons are:
>>>
>>> Since the debugging process is MSVC compiler, there is no DWARF debugging
>>> information. So lldb get __jit_debug_register_code and
>>> __it_debug_descriptor symbol debugging process fails, and
>>> __jit_debug_register_code not support MSVC.
>>> I do not know whether correct?
>>>
>>> ------------------ original message------------------
>>> *From:*"Tamas Berghammer";tberghammer at google.com;
>>> Date*:*2015年11月19日 PM 8:37
>>> *receive:* " "<haifeng_q at foxmail.com>; "lldb-dev"<
>>> lldb-dev at lists.llvm.org>;
>>> *Subject:* Re: [lldb-dev] lldb debug jit-compiled code with llvm on
>>> windows
>>>
>>> In theory you don't have to do anything special to debug some JIT-ed
>>> code as everything should just work (based on the gdb jit interface). In
>>> practice I tried it out a few days ago and it wasn't working at all even in
>>> the case when the application is launched under LLDB (not with attach).
>>> LLDB was understanding the eh_frame for the JIT-ed code but didn't found
>>> the debug info for unknown reason. We should investigate it and try to fix
>>> it sometime. We (lldb for android developers) plan to do it sometime but if
>>> you are interested in it then please feel free to take a look and let us
>>> know if you have any question.
>>>
>>> Tamas
>>>
>>> On Thu, Nov 19, 2015 at 8:40 AM haifeng_q via lldb-dev <
>>> lldb-dev at lists.llvm.org> wrote:
>>>
>>>> hi,
>>>> process A generate function Func1 code with llvm jit compiler, and calls
>>>> Func1. modeled on "Kaleidoscope: Adding Debug Information" add debug
>>>> information. how to use LLDB to attach process A to debug this function
>>>> , add a breakpoint in the function?
>>>>
>>>> thanks!
>>>> _______________________________________________
>>>> lldb-dev mailing list
>>>> lldb-dev at lists.llvm.org
>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
>>>>
>>> _______________________________________________
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>>
>
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