On Fri, 17 Feb 2023, Patrick Palka wrote:
> On Fri, 17 Feb 2023, Marek Polacek wrote:
>
> > On Fri, Feb 17, 2023 at 03:00:39PM -0500, Patrick Palka wrote:
> > > On Fri, 17 Feb 2023, Marek Polacek via Gcc-patches wrote:
> > >
> > > > Here we crash in is_capture_proxy:
> > > >
> > > > /* Location wrappers should be stripped or otherwise handled by the
> > > > caller before using this predicate. */
> > > > gcc_checking_assert (!location_wrapper_p (decl));
> > > >
> > > > so fixed as the comment suggests. We only crash with the redundant
> > > > capture:
> > > >
> > > > int abyPage = [=, abyPage] { ... }
> > > >
> > > > because prune_lambda_captures is only called when there was a default
> > > > capture, and with [=] only abyPage won't be in LAMBDA_EXPR_CAPTURE_LIST.
> > >
> > > It's weird that we even get this far in var_to_maybe_prune. Shouldn't
> > > LAMBDA_CAPTURE_EXPLICIT_P be true for abyPage?
> >
> > Ug, I was seduced by the ostensible obviousness and failed to notice
> > that check. In that light, the correct fix ought to be this. Thanks!
> >
> > Bootstrap/regtest running on x86_64-pc-linux-gnu, ok for trunk if it
> > passes?
> >
> > -- >8 --
> > Here we crash in is_capture_proxy:
> >
> > /* Location wrappers should be stripped or otherwise handled by the
> > caller before using this predicate. */
> > gcc_checking_assert (!location_wrapper_p (decl));
> >
> > We only crash with the redundant capture:
> >
> > int abyPage = [=, abyPage] { ... }
> >
> > because prune_lambda_captures is only called when there was a default
> > capture, and with [=] only abyPage won't be in LAMBDA_EXPR_CAPTURE_LIST.
> >
> > The problem is that LAMBDA_CAPTURE_EXPLICIT_P wasn't propagated
> > correctly and so var_to_maybe_prune proceeded where it shouldn't.
> >
> > PR c++/108829
> >
> > gcc/cp/ChangeLog:
> >
> > * pt.cc (tsubst_lambda_expr): Propagate LAMBDA_CAPTURE_EXPLICIT_P.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/cpp0x/lambda/lambda-108829.C: New test.
> > ---
> > gcc/cp/pt.cc | 4 ++++
> > gcc/testsuite/g++.dg/cpp0x/lambda/lambda-108829.C | 11 +++++++++++
> > 2 files changed, 15 insertions(+)
> > create mode 100644 gcc/testsuite/g++.dg/cpp0x/lambda/lambda-108829.C
> >
> > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > index b1ac7d4beb4..f747ce877b5 100644
> > --- a/gcc/cp/pt.cc
> > +++ b/gcc/cp/pt.cc
> > @@ -19992,6 +19992,10 @@ tsubst_lambda_expr (tree t, tree args,
> > tsubst_flags_t complain, tree in_decl)
> > if (id_equal (DECL_NAME (field), "__this"))
> > LAMBDA_EXPR_THIS_CAPTURE (r) = field;
> > }
> > +
> > + if (LAMBDA_EXPR_CAPTURE_LIST (r))
> > + LAMBDA_CAPTURE_EXPLICIT_P (LAMBDA_EXPR_CAPTURE_LIST (r))
> > + = LAMBDA_CAPTURE_EXPLICIT_P (LAMBDA_EXPR_CAPTURE_LIST (t));
>
> I'm not sure how the flag works for pack captures but it looks like
> this would only propagate the flag to the last expanded capture if
> the capture was originally a pack.
Testcase:
template<int, class... Ts>
void f(Ts... ts) {
constexpr int IDX_PAGE_SIZE = 4096;
int abyPage = [=, ts...] { return IDX_PAGE_SIZE; }();
}
void h() {
f<1>(0, 1);
}
>
> > }
> >
> > tree type = begin_lambda_type (r);
> > diff --git a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-108829.C
> > b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-108829.C
> > new file mode 100644
> > index 00000000000..e621a0d14d0
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-108829.C
> > @@ -0,0 +1,11 @@
> > +// PR c++/108829
> > +// { dg-do compile { target c++11 } }
> > +
> > +template <int>
> > +void f(void) {
> > + constexpr int IDX_PAGE_SIZE = 4096;
> > + int abyPage = [=, abyPage] { return IDX_PAGE_SIZE; }(); // { dg-error
> > "redundant" }
> > +}
> > +void h() {
> > + f<1>();
> > +}
> >
> > base-commit: 5fea1be820508e1fbc610d1a54b61c1add33c36f
> > --
> > 2.39.2
> >
> >
>
