Re: C++ PATCH for c++/69379 (ICE with PTRMEM_CST wrapped in NOP_EXPR)

[Marek Polacek <polacek at redhat dot com>]

On Thu, Jan 21, 2016 at 01:49:14PM -0500, Jason Merrill wrote:
> On 01/21/2016 01:25 PM, Marek Polacek wrote:
> >The problem in this PR is that we have a PTRMEM_CST wrapped in NOP_EXPR
> >and fold_convert can't digest that.
> 
> Why didn't we fold away the NOP_EXPR before calling fold_convert?  I guess
> we shouldn't call fold_convert on an un-folded operand.

So we start with fargs[j] = maybe_constant_value (argarray[j]); in
build_over_call, where argarray[j] is
(const struct 
{
  void Dict::<T462> (struct Dict *, int) * __pfn;
  long int __delta;
} &) &TARGET_EXPR <D.2347, (struct d) <<< Unknown tree: ptrmem_cst >>>>

Later on, we end up in cxx_eval_constant_expression with
t == (struct d) <<< Unknown tree: ptrmem_cst >>>
so we go to the
3607     case NOP_EXPR:
case.  Here cxx_eval_constant_expression evaluates the inner ptrmem_cst,
then there's
3619         if (TREE_CODE (op) == PTRMEM_CST
3620             && !TYPE_PTRMEM_P (type))
3621           op = cplus_expand_constant (op);
but that doesn't trigger, because type is TYPE_PTRMEM_P.
Then we fold () the whole expression but that doesn't change the expression
(and I don't think it should do anything with C++-specific PTRMEM_CST) so we're
stuck with NOP_EXPR around PTRMEM_CST.

So maybe cxx_eval_constant_expression should handle PTRMEM_CSTs wrapped in
NOP_EXPR specially, but I don't know how.

	Marek