Re: [PATCH] c++: ICE with redundant capture [PR108829]

[Patrick Palka <ppalka@redhat.com>]

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?

> 
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/12?
> 
> 	PR c++/108829
> 
> gcc/cp/ChangeLog:
> 
> 	* lambda.cc (var_to_maybe_prune): Strip location wrappers before
> 	checking for a capture proxy.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/cpp0x/lambda/lambda-108829.C: New test.
> ---
>  gcc/cp/lambda.cc                                  |  1 +
>  gcc/testsuite/g++.dg/cpp0x/lambda/lambda-108829.C | 11 +++++++++++
>  2 files changed, 12 insertions(+)
>  create mode 100644 gcc/testsuite/g++.dg/cpp0x/lambda/lambda-108829.C
> 
> diff --git a/gcc/cp/lambda.cc b/gcc/cp/lambda.cc
> index c752622816d..a12b9c183c2 100644
> --- a/gcc/cp/lambda.cc
> +++ b/gcc/cp/lambda.cc
> @@ -1700,6 +1700,7 @@ var_to_maybe_prune (tree cap)
>      return NULL_TREE;
>  
>    tree init = TREE_VALUE (cap);
> +  STRIP_ANY_LOCATION_WRAPPER (init);
>    if (is_normal_capture_proxy (init))
>      init = DECL_CAPTURED_VARIABLE (init);
>    if (decl_constant_var_p (init))
> 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: 6245441e124846d0c3551f312d2feef598fe251c
> -- 
> 2.39.2
> 
>