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.
> }
>
> 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
>
>
