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

[David Blaikie via cfe-dev]

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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