[Bug c++/65300] New: If one more constructor is defined, default params on using not passed from parent class

[Bug c++/65300] New: If one more constructor is defined, default params on using not passed from parent class

[webmatematika at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65300

            Bug ID: 65300
           Summary: If one more constructor is defined, default params on
                    using not passed from parent class
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: webmatematika at hotmail dot com

Created attachment 34937
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34937&action=edit
gcc t.cpp --std=c++11

I am wondering why class B compiles without problems, but class C shows errors
on c4 construction, as default arguments are not passed. If this is by
Standard, could you point me to that paragraph? Thank you for your time.

t.cpp: In function ‘int main()’:
t.cpp:24:4: error: no matching function for call to ‘C::C()’
  C c4;
    ^
t.cpp:24:4: note: candidates are:
t.cpp:13:12: note: C::C(int, int)
   using A::A;
            ^
t.cpp:13:12: note:   candidate expects 2 arguments, 0 provided
t.cpp:13:12: note: C::C(int)
t.cpp:13:12: note:   candidate expects 1 argument, 0 provided
t.cpp:14:3: note: C::C(int, int, int)
   C(int c1, int c2, int c3) : A(c1, c2) {}
   ^
t.cpp:14:3: note:   candidate expects 3 arguments, 0 provided
t.cpp:11:7: note: constexpr C::C(const C&)
 class C : public A {
       ^
t.cpp:11:7: note:   candidate expects 1 argument, 0 provided
t.cpp:11:7: note: constexpr C::C(C&&)
t.cpp:11:7: note:   candidate expects 1 argument, 0 provided
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From: "law at redhat dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug middle-end/65289] [5 regression] ICE when compiling libjpegturbo with -floop-nest-optimize
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ide289

Jeffrey A. Law <law at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P4
                 CC|                            |law at redhat dot com

--- Comment #3 from Jeffrey A. Law <law at redhat dot com> ---
Graphite issue, thus P4.

[Bug c++/65300] If one more constructor is defined, default params on using not passed from parent class

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65300

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This is the same as PR 65291, but I stated the reason wrong there.

Default constructors have special rules. A constructor like C(int = 0) or
C(int = 0, int = 0) will not declare a default constructor when inherited. You
need to declare it explicitly:

  C() = default;

See [class.inhctor] in the standard.

[Bug c++/65300] If one more constructor is defined, default params on using not passed from parent class

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65300

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Sigh, I still got it wrong, sorry!

The default ctor is suppressed, because you declared:

  C(int c1, int c2, int c3) : A(c1, c2) {}

The solution is still to declare it explicitly:

  C() = default;

[Bug c++/65300] If one more constructor is defined, default params on using not passed from parent class

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65300

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
[class.inhctor]/3:

For each non-template constructor in the candidate set of inherited
constructors other than a constructor having no parameters or a copy/move
constructor having a single parameter, a constructor is implicitly declared
with the same constructor characteristics unless there is a user-declared
constructor with the same
signature in the complete class where the using-declaration appears or the
constructor would be a default, copy, or move constructor for that class. 

So inheriting constructors can't declare default, copy or move constructors,
and the presence of another constructor in the class suppresses the implicit
declaration of a default constructor.

[Bug c++/65300] If one more constructor is defined, default params on using not passed from parent class

[webmatematika at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65300

--- Comment #4 from webmatematika at hotmail dot com ---
Thanks for time and explanation.