On 19 Oct 2024, at 11:09, Simon Martin wrote:
> We currently ICE in checking mode with cxx_dialect < 17 on the
> following
> valid code
>
> === cut here ===
> struct X {
> X(const X&) {}
> };
> extern X x;
> void foo () {
> new X[1]{x};
> }
> === cut here ===
>
> The problem is that cp_gimplify_expr gcc_checking_asserts that a
> TARGET_EXPR is not TARGET_EXPR_ELIDING_P (or cannot be elided), while
> in
> this case with cxx_dialect < 17, it is TARGET_EXPR_ELIDING_P but we
> have
> not even tried to elide.
>
> This patch relaxes that gcc_checking_assert to not fail when using
> cxx_dialect < 17 and -fno-elide-constructors (I considered being more
> clever at setting TARGET_EXPR_ELIDING_P appropriately but it looks
> more
> risky and not worth the extra complexity for a checking assert).
>
> Successfully tested on x86_64-pc-linux-gnu.
Friendly ping. Thanks!
>
> PR c++/114619
>
> gcc/cp/ChangeLog:
>
> * cp-gimplify.cc (cp_gimplify_expr): Relax gcc_checking_assert
> to support the usage of -fno-elide-constructors with c++ < 17.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/init/no-elide3.C: New test.
>
> ---
> gcc/cp/cp-gimplify.cc | 7 ++++++-
> gcc/testsuite/g++.dg/init/no-elide3.C | 11 +++++++++++
> 2 files changed, 17 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/g++.dg/init/no-elide3.C
>
> diff --git a/gcc/cp/cp-gimplify.cc b/gcc/cp/cp-gimplify.cc
> index 003e68f1ea7..354ea73c63b 100644
> --- a/gcc/cp/cp-gimplify.cc
> +++ b/gcc/cp/cp-gimplify.cc
> @@ -908,7 +908,12 @@ cp_gimplify_expr (tree *expr_p, gimple_seq
> *pre_p, gimple_seq *post_p)
> gimplify_init_ctor_preeval can materialize subobjects of a
> CONSTRUCTOR
> on the rhs of an assignment, as in constexpr-aggr1.C. */
> gcc_checking_assert (!TARGET_EXPR_ELIDING_P (*expr_p)
> - || !TREE_ADDRESSABLE (TREE_TYPE (*expr_p)));
> + || !TREE_ADDRESSABLE (TREE_TYPE (*expr_p))
> + /* If we explicitly asked not to elide and it's not
> + required by the standard, we can't expect elision
> + to have happened. */
> + || (cxx_dialect < cxx17
> + && !flag_elide_constructors));
> ret = GS_UNHANDLED;
> break;
>
> diff --git a/gcc/testsuite/g++.dg/init/no-elide3.C
> b/gcc/testsuite/g++.dg/init/no-elide3.C
> new file mode 100644
> index 00000000000..9377d9f0161
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/init/no-elide3.C
> @@ -0,0 +1,11 @@
> +// PR c++/114619
> +// { dg-do "compile" { target c++11 } }
> +// { dg-options "-fno-elide-constructors" }
> +
> +struct X {
> + X(const X&) {}
> +};
> +extern X x;
> +void foo () {
> + new X[1]{x};
> +}
> --
> 2.44.0
