[Bug c++/15172] New: Copy constructor optimization in aggregate initialization

[michael dot spencer at ubs dot com]

gcc configured with: --with-gnu-as --with-gnu-ld

A class member of an aggregate appears to be initialized in temporary
storage then byte-copied to its final location, as this code shows:

  int printf (const char *format, ...);

  struct A {
    A * _this;
    A () : _this (this)
    { printf ("A ()          : this = %p, _this = %p\n", this, _this); }
    ~ A ()
    { printf ("~ A ()        : this = %p, _this = %p\n", this, _this); }
    void print ()
    { printf ("print ()      : this = %p, _this = %p\n", this, _this); }

    A (const A & a) : _this (this)
    { printf ("A (const A &) : this = %p, _this = %p\n", this, _this); }
  };

  struct B {
    A a;
  };

  B b = { A () };

  int main () {
    b.a.print ();
  }

When run, the program produces:

  A ()          : this = ffbeae00, _this = ffbeae00
  print ()      : this = 20e2c, _this = ffbeae00
  ~ A ()        : this = 20e2c, _this = ffbeae00

I expected to see the "_this" member compare with "this" in all cases.
In gcc 2.95 this is true.

12.6.1p2 of the Standard states that class members of aggregates are
copy-initialized in this context.

-- 
           Summary: Copy constructor optimization in aggregate
                    initialization
           Product: gcc
           Version: 3.3.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: michael dot spencer at ubs dot com
                CC: gcc-bugs at gcc dot gnu dot org,michael dot spencer at
                    ubs dot com
 GCC build triplet: sparc-sun-solaris2.8
  GCC host triplet: sparc-sun-solaris2.8
GCC target triplet: sparc-sun-solaris2.8


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15172