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

[David Blaikie via cfe-dev]

*nod* One workaround would be to avoid dynamic class templates with enum
parameters - use integer parameters instead. Though admittedly this might
be a rather difficult/annoying workaround if they're used pervasively (or
impossible if these APIs are outside your control).

- Dave

On Tue, Jan 30, 2018 at 9:16 AM Roman Popov <ripopov at gmail.com> wrote:

> 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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>>
>
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