[Bug c++/53288] New: [C++11] Reference fails to bind directly to prvalue member access expression

[hstong at ca dot ibm.com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53288

             Bug #: 53288
           Summary: [C++11] Reference fails to bind directly to prvalue
                    member access expression
    Classification: Unclassified
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: hstong@ca.ibm.com
              Host: powerpc64-unknown-linux-gnu
            Target: powerpc64-unknown-linux-gnu


In the reference initialization,
   const B &b = A(1).b;
the initializer expression is a class prvalue.

The requirement to bind an lvalue reference to a non-volatile const type
directly to a reference-compatible class prvalue dates back to DR 391 which
PR 25950 intended to implement.

The error messages complaining about the private and deleted move constructor
indicate that direct binding was not done.


### Self-contained source (tempbind_expr_ref.cpp):> cat tempbind_expr_ref.cpp
extern "C" int printf(const char *, ...);

struct B {
   B(int data) : _data(data) {
printf("ctor B(int) body:       (this=%p,_data=%d)\n", (void *)this, _data);
   }
   ~B() {
printf("dtor for B:             (this=%p,_data=%d)\n", (void *)this, _data);
   }

   int _data;

private:
   B() = delete;
   B(const B &) = delete;
   B(B &&) = delete;
};

struct A {
   B b;
   A(int data) : b(data) {
printf("ctor A(int) body:       (this=%p,_data=%d)\n", (void *)this, b._data);
   }
   ~A() {
printf("dtor for A:             (this=%p,_data=%d)\n", (void *)this, b._data);
   }

private:
   A() = delete;
   A(const A &) = delete;
   A(A &&) = delete;
};

const B &b = A(1).b;

int main() {
    printf("main() user body begins\n");
    printf("main() user body ends\n");
}


### Compiler invocation:
g++-4.6.0 tempbind_expr_ref.cpp -std=c++0x


### Compiler output:
tempbind_expr_ref.cpp:16:4: error: 'B::B(B&&)' is private
tempbind_expr_ref.cpp:34:19: error: within this context
tempbind_expr_ref.cpp:34:19: error: use of deleted function 'B::B(B&&)'
tempbind_expr_ref.cpp:16:4: error: declared here


### g++ -v output:> g++-4.6.0 -v
Using built-in specs.
COLLECT_GCC=g++-4.6.0
COLLECT_LTO_WRAPPER=/data/gcc/libexec/gcc/powerpc64-unknown-linux-gnu/4.6.0/lto-wrapper
Target: powerpc64-unknown-linux-gnu
Configured with: ./configure --prefix=/data/gcc --program-suffix=-4.6.0
--disable-libssp --disable-libgcj --enable-version-specific-runtime-libs
--with-cpu=default32 --enable-secureplt --with-long-double-128 --enable-shared
--enable-__cxa_atexit --enable-threads=posix --enable-languages=c,c++,fortran
--with-gmp=/usr/local
Thread model: posix
gcc version 4.6.0 (GCC)