[lldb-dev] Question on assert

[Todd Fiala via lldb-dev]

I'm re-running the tests to make sure, but I think that fixed it.  I had
always seen it at least once on test runs locally, but didn't see it on the
last one.

On Thu, Oct 15, 2015 at 8:10 AM, Todd Fiala <todd.fiala at gmail.com> wrote:

> Okay!  I'll give that a shot now and report back what I find.
>
> Thanks, Tamas :-)
>
> -Todd
>
> On Thu, Oct 15, 2015 at 3:37 AM, Tamas Berghammer <tberghammer at google.com>
> wrote:
>
>> Hi Todd,
>>
>> The 64 bit ID of a DIE is built up in the following way:
>> * The offset of the DIE is in the lower 32 bit
>> * If we are using SymbolFileDWARF then the higher 32 bit is the offset of
>> the compile unit this DIE belongs to
>> * If we are using SymbolFileDWARFDwo then the higher 32 bit is the offset
>> of the base compile unit in the parent SymbolFileDWARF
>> * If we are using SymbolFileDWARFDebugMap then the higher 32 bit is the
>> ID of the SymbolFileDWARF this DIE belongs to
>> * If the higher 32 bit is 0 then that means that the source of the DIE
>> isn't specified
>>
>> The assert then tries to verify that one of the following conditions
>> holds:
>> * The higher 32 bit of "id" is 0 what means that we don't have a symbol
>> file pointer (AFAIK shouldn't happen) or we are coming from a
>> SymbolFileDWARF
>> * The higher 32 bit of "cu_id" is 0 what means that the compile unit is
>> at 0 offset what is the case for the single compile units in
>> SymbolFileDWARFDwo (and I think for SymbolFileDWARFDebugMap)
>> * The higher 32 bit of "id" (what is the ID of the SymbolFileDWARF we are
>> belonging to) matches with the higher 32 bit of "cu_id" (what is the offset
>> of the compile unit in the base object file)
>>
>> After thinking a bit more about the assert I think the problem is that
>> the way I calculate cu_id is incompatible for the case when we are using
>> SymbolFileDWARFDebugMap.
>>
>> I think changing line 188 to the following should fix the issue:
>> lldb::user_id_t cu_id = m_cu->GetID()&0xffffffff00000000ull;
>>
>> Please give it a try on OSX and let me know if it helps. I tested it on
>> Linux and it isn't cause any regression there.
>>
>> Thanks,
>> Tamas
>>
>> On Wed, Oct 14, 2015 at 9:13 PM Todd Fiala <todd.fiala at gmail.com> wrote:
>>
>>> Hi Tamas,
>>>
>>> There is an assert in DWARFDIE.cpp (lines 189 - 191) that we're hitting
>>> on the OS X side somewhat frequently nowadays:
>>>
>>>             assert ((id&0xffffffff00000000ull) == 0 ||
>>>
>>>                     (cu_id&0xffffffff00000000ll) == 0 ||
>>>
>>>                     (id&0xffffffff00000000ull) == (cu_id&
>>> 0xffffffff00000000ll));
>>>
>>>
>>> It does not seem to get hit consistently.  We're trying to tease apart
>>> what it is trying to do.  It's a bit strange since it is saying that the
>>> assert should not fire if any one of three clauses is true.  But it's hard
>>> to figure out what exactly is going on there.
>>>
>>>
>>> Can you elucidate what this is trying to do?  Thanks!
>>>
>>> --
>>> -Todd
>>>
>>
>
>
> --
> -Todd
>



-- 
-Todd
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