[Bug c++/22013] Default value in template argument list breaks RTTI lookup

["jwakely.gcc at gmail dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=22013

Jonathan Wakely <jwakely.gcc at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jwakely.gcc at gmail dot com

--- Comment #3 from Jonathan Wakely <jwakely.gcc at gmail dot com> ---
Reduced example:

template<typename>
    struct PolymorphicType
    {
        virtual ~PolymorphicType() {}

        int value;
    };

template <typename, int = 1000>
    struct ATemplate
    {
        struct NestedType { };
    };

int main()
{
    auto poly = new PolymorphicType<ATemplate<long>::NestedType>();

    return poly->value;
}


$ g++ -ggdb3 test.cc -Wall -Wextra 
$ gdb -q -ex start -ex n -ex n -ex "p poly.value" \
  -ex 'python print(str(gdb.parse_and_eval("poly").type.target()))' \
  a.out
Reading symbols from a.out...done.
Temporary breakpoint 1 at 0x400620: file test.cc, line 17.
Starting program: /tmp/a.out 

Temporary breakpoint 1, main () at test.cc:17
17          auto poly = new PolymorphicType<ATemplate<long>::NestedType>();
19          return poly->value;
20      }
warning: RTTI symbol not found for class 'PolymorphicType<ATemplate<long,
1000>::NestedType>'
$1 = 0
PolymorphicType<ATemplate<long>::NestedType>
(gdb) 


An example using a C++17 "template<auto>" type shows a similar problem, GDB
looks for RTTI for AutoTemplate<1u> but the typename is AutoTemplate<1> (which
is arguably a GCC bug, see https://gcc.gnu.org/ml/gcc/2018-02/msg00026.html):

template<typename>
    struct PolymorphicType
    {
        virtual ~PolymorphicType() {}

        int value;
    };

template <auto>
    struct AutoTemplate
    {
    };

int main()
{
    auto poly = new PolymorphicType<AutoTemplate<1u>>();

    return poly->value;
}
$ g++ -ggdb3 -std=c++17 auto.cc -Wall -Wextra
$ gdb -q -ex start -ex n -ex n -ex "p poly.value" \
  -ex 'python print(str(gdb.parse_and_eval("poly").type.target()))' \
  a.out
Reading symbols from a.out...done.
Temporary breakpoint 1 at 0x400620: file auto.cc, line 16.
Starting program: /tmp/a.out 

Temporary breakpoint 1, main () at auto.cc:16
16          auto poly = new PolymorphicType<AutoTemplate<1u>>();
18          return poly->value;
19      }
warning: RTTI symbol not found for class 'PolymorphicType<AutoTemplate<1u> >'
$1 = 0
PolymorphicType<AutoTemplate<1> >
(gdb)

-- 
You are receiving this mail because:
You are on the CC list for the bug.