Hi,
On 3 Jan 2025, at 21:00, Simon Martin wrote:
> We currently accept this code with c++ <= 17 even though it's invalid
> since the base is not initialized (we properly reject it with c++ >=
> 20)
>
> === cut here ===
> struct NoMut1 { int a, b; };
> struct NoMut3 : NoMut1 {
> constexpr NoMut3(int a, int b) {}
> };
> void mutable_subobjects() {
> constexpr NoMut3 nm3(1, 2);
> }
> === cut here ===
>
> This is a fallout of r0-118700-gc2b3ec18a494e3, that ignores all
> fields
> with DECL_ARTIFICIAL in cx_check_missing_mem_inits, including those
> that
> represent base classes, and need to be checked.
>
> This patch makes sure that we only skip fields that have
> DECL_ARTIFICIAL
> if they don't have DECL_FIELD_IS_BASE.
>
> Successfully tested on x86_64-pc-linux-gnu.
Friendly ping.
Thanks! Simon
>
> PR c++/118239
>
> gcc/cp/ChangeLog:
>
> * constexpr.cc (cx_check_missing_mem_inits): Don't skip fields
> with DECL_FIELD_IS_BASE.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/cpp0x/constexpr-base8.C: New test.
>
> ---
> gcc/cp/constexpr.cc | 8 +++----
> gcc/testsuite/g++.dg/cpp0x/constexpr-base8.C | 24
> ++++++++++++++++++++
> 2 files changed, 28 insertions(+), 4 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-base8.C
>
> diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
> index c8be5a525ee..e11444438d3 100644
> --- a/gcc/cp/constexpr.cc
> +++ b/gcc/cp/constexpr.cc
> @@ -839,9 +839,8 @@ cx_check_missing_mem_inits (tree ctype, tree body,
> bool complain)
> if (i < nelts)
> {
> index = CONSTRUCTOR_ELT (body, i)->index;
> - /* Skip base and vtable inits. */
> - if (TREE_CODE (index) != FIELD_DECL
> - || DECL_ARTIFICIAL (index))
> + /* Skip vtable inits. */
> + if (TREE_CODE (index) != FIELD_DECL)
> continue;
> }
>
> @@ -852,7 +851,8 @@ cx_check_missing_mem_inits (tree ctype, tree body,
> bool complain)
> continue;
> if (DECL_UNNAMED_BIT_FIELD (field))
> continue;
> - if (DECL_ARTIFICIAL (field))
> + /* Artificial fields can be ignored unless they're bases. */
> + if (DECL_ARTIFICIAL (field) && !DECL_FIELD_IS_BASE (field))
> continue;
> if (ANON_AGGR_TYPE_P (TREE_TYPE (field)))
> {
> diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-base8.C
> b/gcc/testsuite/g++.dg/cpp0x/constexpr-base8.C
> new file mode 100644
> index 00000000000..ecc28693315
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-base8.C
> @@ -0,0 +1,24 @@
> +// PR c++/118239
> +// { dg-do "compile" { target c++11 } }
> +
> +struct NoMut1 {
> + int a, b;
> +};
> +
> +// Reported case.
> +struct NoMut2 : NoMut1 {
> + constexpr NoMut2(int a, int b) /*: NoMut1()*/
> + {} // { dg-error "must be initialized" "" { target c++17_down } }
> +};
> +
> +// Variant with explicit initialization of some member.
> +struct NoMut3 : NoMut1 {
> + constexpr NoMut3(int a, int b) : c(0) /*, NoMut1()*/
> + {} // { dg-error "must be initialized" "" { target c++17_down } }
> + int c;
> +};
> +
> +void mutable_subobjects() {
> + constexpr NoMut2 nm2(1, 2); // { dg-error "constant expression" }
> + constexpr NoMut3 nm3(1, 2); // { dg-error "constant expression" }
> +}
> --
> 2.44.0
