https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100209
Bug ID: 100209
Summary: multiple inheritance with crtp pattern fails on
sequentioal member access
Product: gcc
Version: 10.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: autumn.rain at mail dot ru
Target Milestone: ---
If multiple inheritance is used with CRTP pattern in a constexpr context,
resulting class is failed to create.
When deriving AB from a single class (also with mani accessors) the constexpr
context is working well.
The error is reproduced on gcc since 6.1.x on any platform.
D:\>D:\0W\00Tools\2GCC_10.2_2020q4\bin\arm-none-eabi-g++ -Wall D:\Test.cpp
D:\Test.cpp:26:60: error: '*(const __ab_t*)(&(&
__ab_t().__ab_t::<anonymous>.__a
_t<__ab_t>::SetA(100))->__ab_t::<anonymous>.__b_t<__ab_t>::SetB(10))' is not a
c
onstant expression
26 | static constexpr const auto AB = __ab_t().SetA(100).SetB(10);
| ^
gcc version
10.2.1
template<typename TDERIVED>
struct __a_t
{
unsigned char A = 0;
constexpr TDERIVED & SetA(const unsigned char & value) { A = value;
return *static_cast<TDERIVED *>(this); }
constexpr __a_t() {}
};
template<typename TDERIVED>
struct __b_t
{
unsigned char B = 0;
constexpr TDERIVED & SetB(const unsigned char & value) { B = value;
return *static_cast<TDERIVED *>(this); }
constexpr __b_t() {}
};
class __ab_t: public __a_t<__ab_t>, public __b_t<__ab_t>
{
public:
constexpr __ab_t(){}
};
static constexpr const auto AB = __ab_t().SetA(100).SetB(10);
int A = 0;
int main()
{
A = AB.A;
}
How-To-Repeat:
Compile the attached code
