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 (_OPERAND (stmt, 1), walk_subtrees,
> > > > data))
> > > > + return error_mark_node;
> > > > + if (TREE_OPERAND (stmt, 2)
> > > > + && cp_fold_immediate_r (_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.
> > > > + break;
> > > > +
> > > >case PTRMEM_CST:
> > > > if (TREE_CODE (PTRMEM_CST_MEMBER (stmt)) == FUNCTION_DECL
> > > > && DECL_IMMEDIATE_FUNCTION_P (PTRMEM_CST_MEMBER (stmt)))
> > > > {
> > > > - if (!data->pset.add (stmt))
> > > > + if (!data->pset.add (stmt) && (complain & tf_error))
> > > > error_at (PTRMEM_CST_LOCATION (stmt),
> > > > "taking address of an immediate function %qD",
> > > > PTRMEM_CST_MEMBER (stmt));
> > > > stmt = *stmt_p = build_zero_cst (TREE_TYPE (stmt));
> > >
> > > It looks like this will overwrite *stmt_p even if we didn't give an error.
> >
> > I suppose that could result in missing errors, adjusted. And there's no
> > point in setting stmt.
> > > > - break;
> > > > + return error_mark_node;
> > > > }
> > > > break;
> > > > +/* Expand immediate invocations. */
> > > > +case CALL_EXPR:
> > > > +case AGGR_INIT_EXPR:
> > > > + if (tree fn = cp_get_callee (stmt))
> > > > + if (TREE_CODE (fn) != ADDR_EXPR || ADDR_EXPR_DENOTES_CALL_P
> > > > (fn))
> > > > + if (tree fndecl = cp_get_fndecl_from_callee (fn,
> > > > /*fold*/false))
> > > > + if (DECL_IMMEDIATE_FUNCTION_P (fndecl))
> > > > + {
> > > > + *stmt_p = stmt = cxx_constant_value (stmt, complain);
> > >
> > > Likewise.
> >
> > I think we have to keep setting *stmt_p to actually evaluate consteval
> > functions.
>
> But only when it succeeds; we don't want to set it to error_mark_node if we
> aren't complaining.
Hmm, probably not. Fixed, thanks.
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. Since in cxx_*
I can't rely on current_function_decl being available, I've added
another walk: a new overload for in_immediate_context that looks into
constexpr_ctx.
You'll see that I've reintroduced ADDR_EXPR_DENOTES_CALL_P here. This
is to detect
*()) ()
(s.*::foo) ()
which were deemed ill-formed.
gcc/cp/ChangeLog:
* call.cc (in_immediate_context): No longer static.
(build_over_call): Set ADDR_EXPR_DENOTES_CALL_P. Don't handle
immediate_invocation_p here.
* constexpr.cc (in_immediate_context): New overload.
(cxx_eval_call_expression): Use mce_true for DECL_IMMEDIATE_FUNCTION_P.
(cxx_eval_conditional_expression): Call cp_fold_immediate.
* cp-gimplify.cc (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:
*
