On Sat, Sep 16, 2023 at 04:22:44PM -0400, Jason Merrill wrote:
> On 9/15/23 16:32, Marek Polacek wrote:
> > On Fri, Sep 15, 2023 at 02:08:46PM -0400, Jason Merrill wrote:
> > > On 9/13/23 20:02, Marek Polacek wrote:
> > > > On Wed, Sep 13, 2023 at 05:57:47PM -0400, Jason Merrill wrote:
> > > > > On 9/13/23 16:56, Marek Polacek wrote:
> > > > > > On Tue, Sep 12, 2023 at 05:26:25PM -0400, Jason Merrill wrote:
> > > > > > > On 9/8/23 14:24, Marek Polacek wrote:
> > > > > > > > + switch (TREE_CODE (stmt))
> > > > > > > > +{
> > > > > > > > +/* Unfortunately we must handle code like
> > > > > > > > +false ? bar () : 42
> > > > > > > > + where we have to check bar too. */
> > > > > > > > +case COND_EXPR:
> > > > > > > > + if (cp_fold_immediate_r (&TREE_OPERAND (stmt, 1),
> > > > > > > > walk_subtrees, data))
> > > > > > > > + return error_mark_node;
> > > > > > > > + if (TREE_OPERAND (stmt, 2)
> > > > > > > > + && cp_fold_immediate_r (&TREE_OPERAND (stmt, 2),
> > > > > > > > walk_subtrees, data))
> > > > > > > > + return error_mark_node;
> > > > > > >
> > > > > > > Is this necessary? Doesn't walk_tree already walk into the arms
> > > > > > > of
> > > > > > > COND_EXPR?
> > > > > >
> > > > > > Unfortunately yes. The cp_fold call in cp_fold_r could fold the ?:
> > > > > > into
> > > > > > a constant before we see it here. I've added a comment saying just
> > > > > > that.
> > > > >
> > > > > Ah. But in that case I guess we need to walk into the arms, not just
> > > > > check
> > > > > the top-level expression in them.
> > > > Arg, of course. I was fooled into thinking that it would recurse, but
> > > > you're right. Fixed by using cp_walk_tree as I intended. Tested in
> > > > consteval34.C.
> > > >
> > > > > But maybe cp_fold_r should do that before the cp_fold, instead of this
> > > > > function?
> > > >
> > > > I...am not sure how that would be better than what I did.
> > >
> > > Callers of cp_fold_immediate don't need this because cp_fold_r isn't
> > > involved, so it isn't folding anything.
> >
> > This is true.
> > > cp_fold_r can walk the arms with cp_fold_r and then clear *walk_subtrees
> > > to
> > > avoid walking the arms again normally.
> >
> > I didn't think we wanted to do everything cp_fold_r does even in dead
> > branches, but ok.
>
> Ah, that's a good point. With the recursive walk in cp_fold_immediate_r, I
> suppose we could suppress it when called from cp_fold_immediate with a new
> fold_flag? That would still allow for cp_walk_tree_without_duplicates.
Yeah, I like that. Done here.
> Incidentally, I notice you check for null op2 of COND_EXPR, should probably
> also check op1.
Added, though I'm not sure it's necessary. I've added some more tests to
consteval34.C to also check for a ?: c.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
-- >8 --
In the review of P2564:
it turned out that in order to correctly handle an example in the paper,
we should stop doing immediate evaluation in build_over_call and
bot_replace, and instead do it in cp_fold_r. This patch does that.
Another benefit is that this is a pretty significant simplification, at
least in my opinion. Also, this fixes the c++/110997 ICE (but the test
doesn't compile yet).
The main drawback seems to be that cp_fold_r doesn't process
uninstantiated templates. We still have to handle things like
"false ? foo () : 1". To that end, I've added cp_fold_immediate, called
on dead branches in cxx_eval_conditional_expression.
You'll see that I've reintroduced ADDR_EXPR_DENOTES_CALL_P here. This
is to detect
*(&foo)) ()
(s.*&S::foo) ()
which were deemed ill-formed.
gcc/cp/ChangeLog:
* call.cc (build_over_call): Set ADDR_EXPR_DENOTES_CALL_P. Don't handle
immediate_invocation_p here.
* constexpr.cc (cxx_eval_call_expression): Use mce_true for
DECL_IMMEDIATE_FUNCTION_P.
(cxx_eval_conditional_expression): Call cp_fold_immediate.
* cp-gimplify.cc (enum fold_flags): Add ff_fold_immediate.
(maybe_replace_decl): Make static.
(cp_fold_r): Expand immediate invocations.
(cp_fold_immediate_r): New.
(cp_fold_immediate): New.
* cp-tree.h (ADDR_EXPR_DENOTES_CALL_P): Define.
(cp_fold_immediate): Declare.
* tree.cc (bot_replace): Don't handle immediate invocations here.
libstdc++-v3/ChangeLog:
* testsuite/20_util/allocator/105975.cc: Add dg-error.
gcc/testsuite/ChangeLog:
* g++.dg/cpp23/consteval-if2.C: Add xfail.
* g++.dg/cpp2a/consteval-memfn1.C: Adjust.
* g++.dg/cpp2a/consteval11.C: Remove dg-message.
* g++.dg/cpp2a/consteval3.C: Remove dg-message and dg-error.
* g++.dg/cpp2a/consteval9.C: Remove dg-message.
* g++.dg/cpp2a/consteval32.C: New test.
* g++.dg/cpp2a/consteval33.C: New test.
* g++.dg/cpp2a/co
