On Wed, Mar 15, 2023 at 12:48:27PM -0400, Jason Merrill wrote:
> On 3/15/23 10:37, Marek Polacek wrote:
> > On Fri, Mar 10, 2023 at 01:47:46PM -0500, Jason Merrill wrote:
> > > On 3/10/23 11:17, Marek Polacek wrote:
> > > > We crash here since r10-3661, the store_init_value hunk in particular.
> > > > Before, we called cp_fully_fold_init, so e.g.
> > > >
> > > > {.str=VIEW_CONVERT_EXPR<char[8]>("")}
> > > >
> > > > was folded into
> > > >
> > > > {.str=""}
> > > >
> > > > but now we don't fold and keep the VCE around, and it causes trouble in
> > > > cxx_eval_store_expression: in the !refs->is_empty () loop we descend on
> > > > .str's initializer but since it's wrapped in a VCE, we skip the
> > > > STRING_CST
> > > > check and then crash on the CONSTRUCTOR_NO_CLEARING.
> > > >
> > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/12?
> > > >
> > > > PR c++/107280
> > > >
> > > > gcc/cp/ChangeLog:
> > > >
> > > > * constexpr.cc (cxx_eval_store_expression): Strip location
> > > > wrappers.
> > > >
> > > > gcc/testsuite/ChangeLog:
> > > >
> > > > * g++.dg/cpp1z/constexpr-lambda28.C: New test.
> > > > ---
> > > > gcc/cp/constexpr.cc | 3 ++-
> > > > gcc/testsuite/g++.dg/cpp1z/constexpr-lambda28.C | 15 +++++++++++++++
> > > > 2 files changed, 17 insertions(+), 1 deletion(-)
> > > > create mode 100644 gcc/testsuite/g++.dg/cpp1z/constexpr-lambda28.C
> > > >
> > > > diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
> > > > index 8683c00596a..abf6ee560c5 100644
> > > > --- a/gcc/cp/constexpr.cc
> > > > +++ b/gcc/cp/constexpr.cc
> > > > @@ -6033,7 +6033,8 @@ cxx_eval_store_expression (const constexpr_ctx
> > > > *ctx, tree t,
> > > > *valp = build_constructor (type, NULL);
> > > > CONSTRUCTOR_NO_CLEARING (*valp) = no_zero_init;
> > > > }
> > > > - else if (TREE_CODE (*valp) == STRING_CST)
> > > > + else if (STRIP_ANY_LOCATION_WRAPPER (*valp),
> > > > + TREE_CODE (*valp) == STRING_CST)
> > >
> > > Seems like this is stripping the location wrapper when we try to modify
> > > the
> > > string; I think we want to strip it earlier, when we first initialize the
> > > array member.
> >
> > Hmm, I suppose we don't want to do the stripping too early. I could
> > have put it in get_nsdmi, for instance, but maybe here is good as well?
>
> I guess I was thinking more around the time when the value is imported into
> constant evaluation, i.e. this chunk of cxx_eval_constant_expression:
>
> > if (tree init = DECL_INITIAL (r))
> > {
> > init = cxx_eval_constant_expression (ctx, init, vc_prvalue,
> > non_constant_p,
> > overflow_p);
> > /* Don't share a CONSTRUCTOR that might be changed. */
> > init = unshare_constructor (init);
> > /* Remember that a constant object's constructor has already
> > run. */
> > if (CLASS_TYPE_P (TREE_TYPE (r))
> > && CP_TYPE_CONST_P (TREE_TYPE (r)))
> > TREE_READONLY (init) = true;
> > ctx->global->put_value (r, init);
> > }
Ah, that wouldn't fix the problem as far as I can tell -- here init is
the whole constructor: {.str=VIEW_CONVERT_EXPR<char[8]>("")} so we'd
not have a way to strip the inner init.
> Feel free to pursue that approach or go ahead and push your first patch,
> whichever you prefer.
The original patch it is, then. Thanks.
Marek
