c++ - inherited protected defaulted constructor is not accessible -


3trying compile code below icc return error: error #453: protected function "a::a()" (declared @ line 10) not accessible through "a" pointer or object.

class { protected:     constexpr a() = default;     ~a() = default;      a(const a&) = delete; };  class b     : protected { public:     b() = default; };  int main() {     b b; }

i found 3 weird ways make compilable:

  • making ctor of public
  • removing deleted copy ctor of a
  • replacing "= default;" "{}" in ctor of a

i mean, why h.. ?

thank answers :)

i confirm misbehaviour on v13.1.3 (linux). compiler bug arne mertz says: find if a provided otherwise pointless data member initialized @ declaration, class compiles, e.g.

class { protected:     constexpr a() = default;     ~a() = default;      a(const a&) = delete;  private:     char placate_intel_compiler_bug = 0; };

i don't know compiler version have, don't know if supports non-static data member initialization (or if same fix work you), if 5th workaround might consider merit intent unmistakable.

removing constexpr has no effect on bug.

of 3 workarounds found third one, replacing defaulted a::a() explicit a::a(){} 1 not mess desired public behaviour of class.

arne mertz's 3b works me 1 has downside of putting solution outside class a.

if in real world have particular reason declaring a::a() constexpr bear in mind, 3rd workaround, if constexpr constructor not default-ed c++11 standard § 7.1.5, para 4, places rather fiddly constraints on constructor , class make code more fragile in maintenance. possible plus in-your-face 5th workaround.


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