On Fri, Feb 03, 2023 at 01:53:48PM -0500, Jason Merrill wrote: > On 2/3/23 13:08, Marek Polacek wrote: > > On Thu, Feb 02, 2023 at 05:29:44PM -0500, Jason Merrill wrote: > > > On 1/30/23 21:35, Marek Polacek wrote: > > > > In this test case, we find ourselves evaluating 't' which is > > > > ((const struct carray *) this)->data_[VIEW_CONVERT_EXPR<long > > > > int>(index)] > > > > in cxx_eval_array_reference. ctx->object is non-null, a RESULT_DECL, so > > > > we replace it with 't': > > > > > > > > new_ctx.object = t; // result_decl replaced > > > > > > > > and then we go to cxx_eval_constant_expression to evaluate an > > > > AGGR_INIT_EXPR, where we end up evaluating an INIT_EXPR (which is in the > > > > body of the constructor for seed_or_index): > > > > > > > > ((struct seed_or_index *) this)->value_ = NON_LVALUE_EXPR <0> > > > > > > > > whereupon in cxx_eval_store_expression we go to the probe loop > > > > where the 'this' is evaluated to > > > > > > > > ze_set.tables_.first_table_.data_[0] > > > > > > > > so the 'object' is ze_set, but that isn't in ctx->global->get_value_ptr > > > > so we fail with a bogus error. ze_set is not there because it comes > > > > from a different constexpr context (it's not in cv_cache either). > > > > > > > > The problem started with r12-2304 where I added the new_ctx.object > > > > replacement. That was to prevent a type mismatch: the type of 't' > > > > and ctx.object were different. > > > > > > > > It seems clear that we shouldn't have replaced ctx.object here. > > > > The cxx_eval_array_reference I mentioned earlier is called from > > > > cxx_eval_store_expression: > > > > 6257 init = cxx_eval_constant_expression (&new_ctx, init, > > > > vc_prvalue, > > > > 6258 non_constant_p, > > > > overflow_p); > > > > which already created a new context, whose .object we should be > > > > using unless, for instance, INIT contained a.b and we're evaluating > > > > the 'a' part, which I think was the case for r12-2304; in that case > > > > ctx.object has to be something different. > > > > > > > > A relatively safe fix should be to check the types before replacing > > > > ctx.object, as in the below. > > > > > > Agreed. I'm trying to understand when the replacement could ever make > > > sense, since 't' is not the target, it's the initializer. The replacement > > > comes from Patrick's fix for 98295, but that testcase no longer hits that > > > code (likely due to changes in empty class handling). > > > > > > If you add a gcc_checking_assert (false) to the replacement, does anything > > > trip it? > > > > It would trip in constexpr-101371.C, added in r12-2304. BUT, and I would > > have sworn that it ICEd when I tried, it's not necessary anymore. So it > > looks like we can simply remove the new_ctx.object line. At least for > > trunk, maybe 12 too. > > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > > OK, thanks. Let's go with your original patch for 11/12.
Will do, thanks. I think I'll wait for a few days before backporting. Marek
