On Mon, 21 Mar 2022, Jason Merrill via Gcc-patches wrote:
> Our C++20 designated initializer handling was broken with members of class
> type; we would find the relevant member and then try to find a member of
> the member with the same name. Or we would sometimes ignore the designator
> entirely. The former problem is fixed by the change to reshape_init_class,
> the latter by the change to reshape_init_r.
>
> Tested x86_64-pc-linux-gnu, applying to trunk.
>
> PR c++/103337
> PR c++/102740
> PR c++/103299
> PR c++/102538
>
> gcc/cp/ChangeLog:
>
> * decl.cc (reshape_init_class): Avoid looking for designator
> after we found it.
> (reshape_init_r): Keep looking for designator.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/ext/flexary3.C: Remove one error.
> * g++.dg/parse/pr43765.C: Likewise.
> * g++.dg/cpp2a/desig22.C: New test.
> * g++.dg/cpp2a/desig23.C: New test.
> * g++.dg/cpp2a/desig24.C: New test.
> * g++.dg/cpp2a/desig25.C: New test.
> ---
> gcc/cp/decl.cc | 47 +++++++++++++++++++++++++---
> gcc/testsuite/g++.dg/cpp2a/desig22.C | 11 +++++++
> gcc/testsuite/g++.dg/cpp2a/desig23.C | 20 ++++++++++++
> gcc/testsuite/g++.dg/cpp2a/desig24.C | 11 +++++++
> gcc/testsuite/g++.dg/cpp2a/desig25.C | 13 ++++++++
> gcc/testsuite/g++.dg/ext/flexary3.C | 2 +-
> gcc/testsuite/g++.dg/parse/pr43765.C | 6 ++--
> 7 files changed, 101 insertions(+), 9 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig22.C
> create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig23.C
> create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig24.C
> create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig25.C
>
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 375385e0013..34d9dad9fb0 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -6598,8 +6598,9 @@ reshape_init_class (tree type, reshape_iter *d, bool
> first_initializer_p,
> {
> tree field_init;
> constructor_elt *old_cur = d->cur;
> + bool direct_desig = false;
>
> - /* Handle designated initializers, as an extension. */
> + /* Handle C++20 designated initializers. */
> if (d->cur->index)
> {
> if (d->cur->index == error_mark_node)
> @@ -6617,7 +6618,10 @@ reshape_init_class (tree type, reshape_iter *d, bool
> first_initializer_p,
> }
> }
> else if (TREE_CODE (d->cur->index) == IDENTIFIER_NODE)
> - field = get_class_binding (type, d->cur->index);
> + {
> + field = get_class_binding (type, d->cur->index);
> + direct_desig = true;
> + }
> else
> {
> if (complain & tf_error)
> @@ -6669,6 +6673,7 @@ reshape_init_class (tree type, reshape_iter *d, bool
> first_initializer_p,
> break;
> gcc_assert (aafield);
> field = aafield;
> + direct_desig = false;
> }
> }
>
> @@ -6683,9 +6688,32 @@ reshape_init_class (tree type, reshape_iter *d, bool
> first_initializer_p,
> assumed to correspond to no elements of the initializer list. */
> goto continue_;
>
> - field_init = reshape_init_r (TREE_TYPE (field), d,
> - /*first_initializer_p=*/NULL_TREE,
> - complain);
> + if (direct_desig)
> + {
> + /* The designated field F is initialized from this one element:
> + Temporarily clear the designator so a recursive reshape_init_class
> + doesn't try to find it again in F, and adjust d->end so we don't
> + try to use the next initializer to initialize another member of F.
> +
> + Note that we don't want these changes if we found the designator
> + inside an anon aggr above; we leave them alone to implement:
> +
> + "If the element is an anonymous union member and the initializer
> + list is a brace-enclosed designated- initializer-list, the element
> + is initialized by the designated-initializer-list { D }, where D
> + is the designated- initializer-clause naming a member of the
> + anonymous union member." */
> + auto end_ = make_temp_override (d->end, d->cur + 1);
> + auto idx_ = make_temp_override (d->cur->index, NULL_TREE);
IIUC this override of d->cur->index mutates the underlying CONSTRUCTOR, which
is probably fine, but I wonder if it'd be worthwhile to avoid the mutation by
using a temporary reshape_iter for the recursive call, something like:
constructor_elt elt = { /*index=*/NULL_TREE, d->cur->value };
reshape_iter iter = { &elt, &elt + 1 };
field_init = reshape_init_r (TREE_TYPE (field), &iter,
/*first_initializer_p=*/NULL_TREE,
complain);
d->cur++;
> + field_init = reshape_init_r (TREE_TYPE (field), d,
> + /*first_initializer_p=*/NULL_TREE,
> + complain);
> + }
> + else
> + field_init = reshape_init_r (TREE_TYPE (field), d,
> + /*first_initializer_p=*/NULL_TREE,
> + complain);
> +
> if (field_init == error_mark_node)
> return error_mark_node;
>
> @@ -6941,6 +6969,15 @@ reshape_init_r (tree type, reshape_iter *d, tree
> first_initializer_p,
> to handle initialization of arrays and similar. */
> else if (COMPOUND_LITERAL_P (stripped_init))
> gcc_assert (!BRACE_ENCLOSED_INITIALIZER_P (stripped_init));
> + /* If we have an unresolved designator, we need to find the member it
> + designates within TYPE, so proceed to the routines below. For
> + FIELD_DECL or INTEGER_CST designators, we're already initializing
> + the designated element. */
> + else if (d->cur->index
> + && TREE_CODE (d->cur->index) == IDENTIFIER_NODE)
> + /* Brace elision with designators is only permitted for anonymous
> + aggregates. */
> + gcc_checking_assert (ANON_AGGR_TYPE_P (type));
> /* A CONSTRUCTOR of the target's type is a previously
> digested initializer. */
> else if (same_type_ignoring_top_level_qualifiers_p (type, init_type))
> diff --git a/gcc/testsuite/g++.dg/cpp2a/desig22.C
> b/gcc/testsuite/g++.dg/cpp2a/desig22.C
> new file mode 100644
> index 00000000000..ba083f8e3d5
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/desig22.C
> @@ -0,0 +1,11 @@
> +// PR c++/103337
> +// { dg-do compile { target c++20 } }
> +
> +struct op_t {
> + struct put_t {
> + int x;
> + } put;
> +};
> +
> +op_t x{0}; // OK
> +op_t y{.put=0}; // bogus error: 'op_t::put_t' has no non-static data member
> named 'put'
> diff --git a/gcc/testsuite/g++.dg/cpp2a/desig23.C
> b/gcc/testsuite/g++.dg/cpp2a/desig23.C
> new file mode 100644
> index 00000000000..4354e644f6a
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/desig23.C
> @@ -0,0 +1,20 @@
> +// PR c++/102740
> +// { dg-do compile { target c++20 } }
> +// { dg-additional-options -Wmissing-braces }
> +
> +typedef struct {
> + union {
> + struct {
> + const void* content;
> + } put;
> + };
> +} op_t;
> +
> +op_t f(const char* alias) {
> + return op_t{
> + .put =
> + {
> + .content = alias,
> + },
> + }; // { dg-warning "missing braces" }
> +}
> diff --git a/gcc/testsuite/g++.dg/cpp2a/desig24.C
> b/gcc/testsuite/g++.dg/cpp2a/desig24.C
> new file mode 100644
> index 00000000000..219cc9c3b8e
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/desig24.C
> @@ -0,0 +1,11 @@
> +// PR c++/103299
> +// { dg-do compile { target c++20 } }
> +
> +struct foo {
> + union {
> + int fp1{};
> + char fp2;
> + };
> +};
> +
> +static_assert(foo{.fp2={}}.fp2 == 0);
> diff --git a/gcc/testsuite/g++.dg/cpp2a/desig25.C
> b/gcc/testsuite/g++.dg/cpp2a/desig25.C
> new file mode 100644
> index 00000000000..9da958c29e9
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/desig25.C
> @@ -0,0 +1,13 @@
> +// PR c++/102538
> +// { dg-do run { target c++20 } }
> +
> +struct X { union { char r8[8]; int r32[2]; }; };
> +struct Y { X v[1]; };
> +Y x = { { { .r32 = { 5, 6 } } } };
> +
> +int
> +main ()
> +{
> + if (x.v[0].r32[0] != 5 || x.v[0].r32[1] != 6)
> + __builtin_abort ();
> +}
> diff --git a/gcc/testsuite/g++.dg/ext/flexary3.C
> b/gcc/testsuite/g++.dg/ext/flexary3.C
> index 34b17254f8c..8344b42dd16 100644
> --- a/gcc/testsuite/g++.dg/ext/flexary3.C
> +++ b/gcc/testsuite/g++.dg/ext/flexary3.C
> @@ -16,7 +16,7 @@ struct s {
>
> int main()
> {
> - struct s s = { .c = 0 }; // { dg-error "initializer" }
> + struct s s = { .c = 0 };
> // { dg-error "non-static initialization of a flexible array member" ""
> { target *-*-* } .-1 }
> return 0;
> }
> diff --git a/gcc/testsuite/g++.dg/parse/pr43765.C
> b/gcc/testsuite/g++.dg/parse/pr43765.C
> index 5e602204007..aa099a4d20b 100644
> --- a/gcc/testsuite/g++.dg/parse/pr43765.C
> +++ b/gcc/testsuite/g++.dg/parse/pr43765.C
> @@ -12,6 +12,6 @@ SomeType vals[] =
> {
> { 0, values : temp, }, // { dg-error "either all initializer
> clauses should be designated or none of them should be" "" { target c++2a } }
> 0
> - }; // { dg-error "GNU-style designated initializer for an array|cannot
> convert" }
> -// (note the error above is on the wrong line)
> - // { dg-error "initialization of flexible array member in a nested
> context" "" { target *-*-* } .-2 }
> + };
> +// (note the error below is on the wrong line)
> +// { dg-error "initialization of flexible array member in a nested context"
> "" { target *-*-* } .-2 }
>
> base-commit: 70b8f43695b0e6fabc760d247ac83f354092b21d
> prerequisite-patch-id: d89344aafac30ce0b8645945beb2d94b7ddb3515
> --
> 2.27.0
>
>
