On Wed, 26 Jun 2024, Simon Martin wrote:
> The case in the ticket is an ICE on invalid due to an assert in
> stabilize_expr,
> but the underlying issue can actually trigger on this *valid* code:
>
> === cut here ===
> struct TheClass {
> TheClass() {}
> TheClass(volatile TheClass& t) {}
> TheClass operator=(volatile TheClass& t) volatile { return t; }
> };
> void the_func() {
> volatile TheClass x, y, z;
> (false ? x : y) = z;
> }
> === cut here ===
>
> The problem is that stabilize_expr asserts that it returns an expression
> without TREE_SIDE_EFFECTS, which can't be if the involved type is volatile.
>
> This patch relaxes the assert to accept having TREE_THIS_VOLATILE on the
> returned expression.
>
> Successfully tested on x86_64-pc-linux-gnu.
>
> PR c++/111160
>
> gcc/cp/ChangeLog:
>
> * tree.cc (stabilize_expr): Stabilized expressions can have
> TREE_SIDE_EFFECTS if they're volatile.
LGTM (although I can't formally approve the patch)
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/overload/error8.C: New test.
> * g++.dg/overload/volatile2.C: New test.
>
> ---
> gcc/cp/tree.cc | 2 +-
> gcc/testsuite/g++.dg/overload/error8.C | 9 +++++++++
> gcc/testsuite/g++.dg/overload/volatile2.C | 12 ++++++++++++
> 3 files changed, 22 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/g++.dg/overload/error8.C
> create mode 100644 gcc/testsuite/g++.dg/overload/volatile2.C
>
> diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
> index 28648c14c6d..dfd4a3a948b 100644
> --- a/gcc/cp/tree.cc
> +++ b/gcc/cp/tree.cc
> @@ -5969,7 +5969,7 @@ stabilize_expr (tree exp, tree* initp)
> }
> *initp = init_expr;
>
> - gcc_assert (!TREE_SIDE_EFFECTS (exp));
> + gcc_assert (!TREE_SIDE_EFFECTS (exp) || TREE_THIS_VOLATILE (exp));
> return exp;
> }
>
> diff --git a/gcc/testsuite/g++.dg/overload/error8.C
> b/gcc/testsuite/g++.dg/overload/error8.C
> new file mode 100644
> index 00000000000..a7e745860e0
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/overload/error8.C
> @@ -0,0 +1,9 @@
> +// PR c++/111160
> +// { dg-do compile { target c++11 } }
> +
> +class TheClass {}; // { dg-error "discards|bind|discards|bind" }
> +void the_func() {
> + TheClass x;
> + volatile TheClass y;
> + (false ? x : x) = y; // { dg-error "ambiguous|ambiguous" }
> +}
> diff --git a/gcc/testsuite/g++.dg/overload/volatile2.C
> b/gcc/testsuite/g++.dg/overload/volatile2.C
> new file mode 100644
> index 00000000000..9f27357aed6
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/overload/volatile2.C
> @@ -0,0 +1,12 @@
> +// PR c++/111160
> +// { dg-do compile { target c++11 } }
> +
> +struct TheClass {
> + TheClass() {}
> + TheClass(volatile TheClass& t) {}
> + TheClass operator=(volatile TheClass& t) volatile { return t; }
> +};
> +void the_func() {
> + volatile TheClass x, y, z;
> + (false ? x : y) = z;
> +}
> --
> 2.44.0
>
>
>
>
