[cfe-dev] Clang generates wrong RTTI or Debug info?

[Roman Popov via cfe-dev]

So this is a well-known Clang bug. And it affects both GDB and LLDB...

Hope it will be fixed soon.
In my case it is a complete show-stopper: I use GDB python scripting for
C++ introspection and Verilog/VHDL code-generation. And it is part of my
build flow.


-Roman

2018-01-29 11:38 GMT-08:00 David Blaikie <dblaikie at gmail.com>:

> This came up not too long ago: https://reviews.llvm.org/D39622
>
> I'm leaning towards accepting at least some uniform naming scheme (rather
> than, say "enum X { Y = 0, Z = 0 };" as a template parameter with foo<Z>
> named as foo<Y> and foo<(X)1> as foo<1> - maybe they should all be, as GCC
> does, foo<(X)N>).
>
> It's a slightly awkward thing to require that the GDB demangler and
> Clang's naming match letter-for-letter (& I think GDB's matching is a bit
> fuzzier than that - I seem to recall seeing it handle some differences in
> whitespace, maybe in parentheses/casts?).
>
> - Dave
>
> On Fri, Jan 26, 2018 at 1:28 PM Roman Popov via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
>
>> I've put the same question on stackoverflow:
>> https://stackoverflow.com/questions/48469750/debugging-
>> clang-generated-rtti-code-with-gdb
>>
>> Maybe GDB is the problem, not Clang?
>>
>>
>> 2018-01-25 21:03 GMT-08:00 Roman Popov <ripopov at gmail.com>:
>>
>>> Hello,
>>>
>>> I'm using Clang++ together with GDB. I've noticed that for some
>>> polymorphic classes GDB does not shows correct dynamic type.  After some
>>> investigation it turned out that Clang puts different typenames in DWARF
>>> and RTTI :
>>>
>>> I have a template class:
>>>
>>> template< class T, sc_writer_policy POL>
>>> class sc_signal : public sc_object
>>>
>>> where sc_writer_policy is an enum:
>>>
>>> enum sc_writer_policy
>>> {
>>>   SC_ONE_WRITER        = 0,
>>>   SC_MANY_WRITERS      = 1,
>>>   SC_UNCHECKED_WRITERS = 3
>>> };
>>>
>>>
>>> When I debug polymorphic objects of this class I got GDB errors like
>>> this:
>>>
>>> warning: RTTI symbol not found for class 'sc_core::sc_signal<int,
>>> (sc_core::sc_writer_policy)0>'
>>>
>>>
>>> The source of the problem is that it type name seems to be saved
>>> differently in RTTI and Debug info.
>>>
>>> From GDB:
>>> (gdb) info types sc_signal<int
>>> All types matching regular expression "sc_signal<int":
>>>
>>> *sc_core::sc_signal<int, sc_core::SC_ONE_WRITER>*
>>>
>>> Using RTTI:
>>>
>>> cout << typeid(*obj).name();
>>> N7sc_core9sc_signalIiLNS_16*sc_writer_policyE0*EEE
>>>
>>> So in RTTI we have mangled sc_core::sc_signal<int,
>>> (sc_core::sc_writer_policy)0>
>>>
>>>
>>> Is it possible to make Clang emitting same type-name in both cases?
>>>
>>>
>>> Originally I've discovered this issue with Clang++5.0.  Just tried with
>>> Clang++6.0 and it is still there.
>>> g++ 5.4 and g++7.0 both work fine, (sc_core::sc_signal<int,
>>> (sc_core::sc_writer_policy)0> is generated in both cases)
>>>
>>> Thanks,
>>> Roman
>>>
>>>
>>>
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