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From: "libremax90 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/59816] New: [c++11] Incorrect visibility check in template instantiation when the default constructor is a variadic template.
Date: Wed, 15 Jan 2014 00:37:00 -0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 4.8.2
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X-Bugzilla-Who: libremax90 at gmail dot com
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X-Bugzilla-Priority: P3
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59816

            Bug ID: 59816
           Summary: [c++11] Incorrect visibility check in template
                    instantiation when the default constructor is a
                    variadic template.
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: libremax90 at gmail dot com

The following C++11 code won't compile on GCC 4.8.2 while clang++ will accept
it without a warning. In the following test case, GCC seems to check Base's
default constructor visibility in the test function's context, where the
templates are instantiated.

class Base {
protected:
  template<class... TArgs>
  Base(TArgs...) {}

  // Uncomment to workaround                                                    
  //Base() {}                                                                   
};

class Class
  : public Base {
public:
  template<class... TArgs>
  Class(TArgs... args) : Base { args... } {}

  // Another workaround:                                                        
  //Class() {}                                                                  
};

void test() {
  Class{};
}

Here is `g++ -v`'s output:

Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-unknown-linux-gnu/4.8.2/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: /build/gcc/src/gcc-4.8-20131219/configure --prefix=/usr
--libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man
--infodir=/usr/share/info --with-bugurl=https://bugs.archlinux.org/
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++ --enable-shared
--enable-threads=posix --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-clocale=gnu --disable-libstdcxx-pch
--disable-libssp --enable-gnu-unique-object --enable-linker-build-id
--enable-cloog-backend=isl --disable-cloog-version-check --enable-lto
--enable-plugin --enable-install-libiberty --with-linker-hash-style=gnu
--disable-multilib --disable-werror --enable-checking=release
Thread model: posix
gcc version 4.8.2 20131219 (prerelease) (GCC)