[Bug c++/34824] [4.1/4.2/4.3 Regression] ICE with explicit copy constructor

["jakub at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #4 from jakub at gcc dot gnu dot org  2008-01-21 20:29 -------
Related testcase:
struct A;

struct B
{
  B (A const &);
  B (B &);
};

struct A
{
  A (B) {}
};

B
f (A const &a)
{
  return B (a);
}

which doesn't have explicit at all segfaults as well, also endless recursion.
In both cases the copy constructor can't be used,
so a conversion through A(B) constructor and then B(const A&) is attempted.
But that needs a temporary, so a B(const B &) copy constructor is needed and
we are back to the original problem.

If A's constructor is instead A (const B &) {}, then it compiles just fine
in both variants ( explicit B (const B &); and B (B &); ).  So I guess we just
need to detect recursion here.  I believe C++ will try only one hop through
some
other class' constructor, so perhaps just remembering one parent type would
be enough to prevent the recursion.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34824