https://gcc.gnu.org/g:ec5605dafee9275eb01b0cea594c6f401061ff82

commit r16-8372-gec5605dafee9275eb01b0cea594c6f401061ff82
Author: Jakub Jelinek <[email protected]>
Date:   Wed Apr 1 00:14:04 2026 +0200

    c++: Handle annotations in data_member_spec/define_aggregate
    
    The following patch attempts to implement another part of P3795R2,
    in particular the addition of annotations to data_member_options
    and handling it in data_member_spec/define_aggregate etc.
    
    2026-03-31  Jakub Jelinek  <[email protected]>
    
    libstdc++-v3/
            * include/std/meta (std::meta::data_member_options): Add annotations
            member.
    gcc/cp/
            * reflect.cc (get_range_elts): If N is negative, just use the tree
            as object to extract range from instead of finding Nth argument
            of a call.
            (eval_is_bit_field, eval_type_of, eval_size_of, eval_alignment_of,
            eval_bit_size_of, eval_has_identifier, eval_identifier_of): Adjust
            function comments from P3795R2.
            (eval_display_string_of): Handle annotations in
            REFLECT_DATA_MEMBER_SPEC.
            (eval_annotations_of): Adjust function comments from P3795R2.
            (eval_data_member_spec): Likewise.  Read and diagnose annotations.
            (eval_define_aggregate): Adjust function comments from P3795R2.
            Create annotations.
            (compare_reflections): Compare REFLECT_DATA_MEMBER_SPEC annotations.
            * mangle.cc (write_reflection): Mangle REFLECT_DATA_MEMBER_SPEC
            annotations.
    gcc/testsuite/
            * g++.dg/reflect/data_member_spec5.C: New test.
            * g++.dg/reflect/data_member_spec6.C: New test.
            * g++.dg/reflect/display_string_of1.C: Expect extra ", {}" before
            closing paren for empty annotations, otherwise a list of 
annotations.
            * g++.dg/reflect/u8display_string_of1.C: Likewise.
            * g++.dg/reflect/define_aggregate9.C: New test.
            * g++.dg/reflect/mangle1.C: Test mangling of 
REFLECT_DATA_MEMBER_SPEC
            annotations.
    
    Reviewed-by: Jason Merrill <[email protected]>
    Reviewed-by: Jonathan Wakely <[email protected]>

Diff:
---
 gcc/cp/mangle.cc                                   |   2 +
 gcc/cp/reflect.cc                                  | 210 +++++++++++++++------
 gcc/testsuite/g++.dg/reflect/data_member_spec5.C   | 114 +++++++++++
 gcc/testsuite/g++.dg/reflect/data_member_spec6.C   |  12 ++
 gcc/testsuite/g++.dg/reflect/define_aggregate9.C   |  35 ++++
 gcc/testsuite/g++.dg/reflect/display_string_of1.C  |   9 +-
 gcc/testsuite/g++.dg/reflect/mangle1.C             |   7 +
 .../g++.dg/reflect/u8display_string_of1.C          |   9 +-
 libstdc++-v3/include/std/meta                      |   1 +
 9 files changed, 335 insertions(+), 64 deletions(-)

diff --git a/gcc/cp/mangle.cc b/gcc/cp/mangle.cc
index 3b8b9ed9d77b..24e1cefbd324 100644
--- a/gcc/cp/mangle.cc
+++ b/gcc/cp/mangle.cc
@@ -4254,6 +4254,8 @@ write_reflection (tree refl)
       write_char ('_');
       if (integer_nonzerop (TREE_VEC_ELT (arg, 4)))
        write_char ('n');
+      for (int i = 5; i < TREE_VEC_LENGTH (arg); ++i)
+       write_template_arg (REFLECT_EXPR_HANDLE (TREE_VEC_ELT (arg, i)));
     }
 }
 
diff --git a/gcc/cp/reflect.cc b/gcc/cp/reflect.cc
index 8687e3f8fe3c..69b236659d89 100644
--- a/gcc/cp/reflect.cc
+++ b/gcc/cp/reflect.cc
@@ -389,18 +389,25 @@ enum get_range_elts_kind {
    eval_reflect_constant_array.  For GET_INFO_VEC kind, <meta> ensures
    the argument is reference to reflection_range concept and so both
    range_value_t is info and range_refernce_t is cv info or cv info & or
-   cv info &&.  */
+   cv info &&.  If N is negative, CALL is the expression to extract
+   values from rather than N-th argument from CALL.  */
 
 static tree
 get_range_elts (location_t loc, const constexpr_ctx *ctx, tree call, int n,
                bool *non_constant_p, bool *overflow_p, tree *jump_target,
                get_range_elts_kind kind, tree fun)
 {
-  gcc_checking_assert (call_expr_nargs (call) > n);
-  tree arg = get_nth_callarg (call, n);
-  tree parm = DECL_ARGUMENTS (cp_get_callee_fndecl_nofold (call));
-  for (int i = 0; i < n; ++i)
-    parm = DECL_CHAIN (parm);
+  tree arg, parm;
+  if (n < 0)
+    arg = parm = call;
+  else
+    {
+      gcc_checking_assert (call_expr_nargs (call) > n);
+      arg = get_nth_callarg (call, n);
+      parm = DECL_ARGUMENTS (cp_get_callee_fndecl_nofold (call));
+      for (int i = 0; i < n; ++i)
+       parm = DECL_CHAIN (parm);
+    }
   tree type = TREE_TYPE (arg);
   gcc_checking_assert (TYPE_REF_P (type));
   arg = cxx_eval_constant_expression (ctx, arg, vc_prvalue, non_constant_p,
@@ -545,7 +552,8 @@ get_range_elts (location_t loc, const constexpr_ctx *ctx, 
tree call, int n,
     tree call = finish_call_expr (obj, &args, true, false, complain);
     if (call == error_mark_node)
       return call;
-    cp_walk_tree (&call, replace_parm_r, map, NULL);
+    if (n >= 0)
+      cp_walk_tree (&call, replace_parm_r, map, NULL);
     if (complain != tf_none)
       return call;
     call = cxx_eval_constant_expression (ctx, call, vc_prvalue, non_constant_p,
@@ -1859,7 +1867,7 @@ eval_is_explicit (tree r)
 
 /* Process std::meta::is_bit_field.
    Returns: true if r represents a bit-field, or if r represents a data member
-   description (T,N,A,W,NUA) for which W is not _|_.  Otherwise, false.  */
+   description (T,N,A,W,NUA,ANN) for which W is not _|_.  Otherwise, false.  */
 
 static tree
 eval_is_bit_field (const_tree r, reflect_kind kind)
@@ -2524,8 +2532,8 @@ type_of (tree r, reflect_kind kind)
         of the enum-specifier as specified in [dcl.enum].
    -- Otherwise, if r represents a direct base class relationship (D,B), then
       a reflection of B.
-   -- Otherwise, for a data member description (T,N,A,W,NUA), a reflection of
-      the type T.  */
+   -- Otherwise, for a data member description (T,N,A,W,NUA,ANN), a reflection
+      of the type T.  */
 
 static tree
 eval_type_of (location_t loc, const constexpr_ctx *ctx, tree r,
@@ -3175,7 +3183,7 @@ eval_offset_of (location_t loc, const constexpr_ctx *ctx, 
tree r,
 /* Process std::meta::size_of.
    Returns: If
      -- r represents a non-static data member of type T or a data member
-       description (T,N,A,W,NUA) or
+       description (T,N,A,W,NUA,ANN) or
      -- dealias(r) represents a type T,
    then sizeof(T) if T is not a reference type and size_of(add_pointer(^^T))
    otherwise.  Otherwise, size_of(type_of(r)).
@@ -3184,7 +3192,7 @@ eval_offset_of (location_t loc, const constexpr_ctx *ctx, 
tree r,
      -- dealias(r) is a reflection of a type, object, value, variable of
        non-reference type, non-static data member that is not a bit-field,
        direct base class relationship, or data member description
-       (T,N,A,W,NUA) where W is not _|_.
+       (T,N,A,W,NUA,ANN) where W is not _|_.
      -- If dealias(r) represents a type, then is_complete_type(r) is true.  */
 
 static tree
@@ -3235,12 +3243,13 @@ eval_size_of (location_t loc, const constexpr_ctx *ctx, 
tree r,
    -- Otherwise, if r represents a non-static data member M of a class C,
       then the alignment of the direct member subobject corresponding to M of a
       complete object of type C.
-   -- Otherwise, r represents a data member description (T,N,A,W,NUA).
+   -- Otherwise, r represents a data member description (T,N,A,W,NUA,ANN).
       If A is not _|_, then the value A.  Otherwise, alignment_of(^^T).
    Throws: meta::exception unless all of the following conditions are met:
    -- dealias(r) is a reflection of a type, object, variable of non-reference
       type, non-static data member that is not a bit-field, direct base class
-      relationship, or data member description (T,N,A,W,NUA) where W is _|_.
+      relationship, or data member description (T,N,A,W,NUA,ANN) where W is
+      _|_.
    -- If dealias(r) represents a type, then is_complete_type(r) is true.  */
 
 static tree
@@ -3309,7 +3318,7 @@ eval_alignment_of (location_t loc, const constexpr_ctx 
*ctx, tree r,
    Returns:
      -- If r represents an unnamed bit-field or a non-static data member that
        is a bit-field with width W, then W.
-     -- Otherwise, if r represents a data member description (T,N,A,W,NUA)
+     -- Otherwise, if r represents a data member description (T,N,A,W,NUA,ANN)
        and W is not _|_, then W.
      -- Otherwise, CHAR_BIT * size_of(r).
 
@@ -3406,8 +3415,8 @@ eval_bit_size_of (location_t loc, const constexpr_ctx 
*ctx, tree r,
       namespace, or namespace alias, then true.
    -- Otherwise, if r represents a direct base class relationship, then
       has_identifier(type_of(r)).
-   -- Otherwise, r represents a data member description (T,N,A,W,NUA); true if
-      N is not _|_.  Otherwise, false.  */
+   -- Otherwise, r represents a data member description (T,N,A,W,NUA,ANN);
+      true if N is not _|_.  Otherwise, false.  */
 
 static tree
 eval_has_identifier (tree r, reflect_kind kind)
@@ -3522,7 +3531,7 @@ eval_has_identifier (tree r, reflect_kind kind)
       the declaration of that entity.
    -- Otherwise, if r represents a direct base class relationship, then
       identifier_of(type_of(r)) or u8identifier_of(type_of(r)), respectively.
-   -- Otherwise, r represents a data member description (T,N,A,W,NUA);
+   -- Otherwise, r represents a data member description (T,N,A,W,NUA,ANN);
       a string_view or u8string_view, respectively, containing the identifier
       N.
    Throws: meta::exception unless has_identifier(r) is true and the identifier
@@ -3649,10 +3658,16 @@ eval_display_string_of (location_t loc, const 
constexpr_ctx *ctx, tree r,
       pp_printf (&pp, "%T: %T", d, BINFO_TYPE (r));
     }
   else if (kind == REFLECT_DATA_MEMBER_SPEC)
-    pp_printf (&pp, "(%T, %E, %E, %E, %s)", TREE_VEC_ELT (r, 0),
-              TREE_VEC_ELT (r, 1), TREE_VEC_ELT (r, 2), TREE_VEC_ELT (r, 3),
-              TREE_VEC_ELT (r, 4) == boolean_true_node
-              ? "true" : "false");
+    {
+      pp_printf (&pp, "(%T, %E, %E, %E, %s, {", TREE_VEC_ELT (r, 0),
+                TREE_VEC_ELT (r, 1), TREE_VEC_ELT (r, 2), TREE_VEC_ELT (r, 3),
+                TREE_VEC_ELT (r, 4) == boolean_true_node
+                ? "true" : "false");
+      for (int i = 5; i < TREE_VEC_LENGTH (r); ++i)
+       pp_printf (&pp, "%s%E", i == 5 ? "" : ", ",
+                  REFLECT_EXPR_HANDLE (TREE_VEC_ELT (r, i)));
+      pp_printf (&pp, "})");
+    }
   else if (eval_is_annotation (r, kind) == boolean_true_node)
     pp_printf (&pp, "[[=%E]]",
               tree_strip_any_location_wrapper (TREE_VALUE (TREE_VALUE (r))));
@@ -3768,15 +3783,21 @@ remove_const (tree type)
 }
 
 /* Process std::meta::annotations_of and annotations_of_with_type.
-   Let E be
-   -- the corresponding base-specifier if item represents a direct base class
-      relationship,
-   -- otherwise, the entity represented by item.
+   For a function F, let S(F) be the set of declarations, ignoring any explicit
+   instantiations, that declare either F or a templated function of which F is
+   a specialization.
    Returns: A vector containing all of the reflections R representing each
-   annotation applying to each declaration of E that precedes either some
-   point in the evaluation context or a point immediately following the
-   class-specifier of the outermost class for which such a point is in a
-   complete-class context.
+   annotation applying to:
+   -- if item represents a function parameter P of a function F, then the
+      declaration of P in each declaration of F in S(F),
+   -- otherwise, if item represents a function F, then each declaration of F
+      in S(F),
+   -- otherwise, if item represents a direct base class relationship (D,B),
+      then the corresponding base-specifier in the definition of D,
+   -- otherwise, each declaration of the entity represented by item,
+   such that precedes either some point in the evaluation context or a point
+   immediately following the class-specifier of the outermost class for which
+   such a point is in a complete-class context.
    For any two reflections R1 and R2 in the returned vector, if the annotation
    represented by R1 precedes the annotation represented by R2, then R1
    appears before R2.
@@ -3785,8 +3806,8 @@ remove_const (tree type)
    from T.
 
    Throws: meta::exception unless item represents a type, type alias,
-   variable, function, namespace, enumerator, direct base class relationship,
-   or non-static data member.  */
+   variable, function, function parameter, namespace, enumerator, direct base
+   class relationship, or non-static data member.  */
 
 static tree
 eval_annotations_of (location_t loc, const constexpr_ctx *ctx, tree r,
@@ -5519,15 +5540,17 @@ eval_variant_alternative (location_t loc, const 
constexpr_ctx *ctx, tree i,
 }
 
 /* Process std::meta::data_member_spec.
-   Returns: A reflection of a data member description (T,N,A,W,NUA) where
+   Returns: A reflection of a data member description (T,N,A,W,NUA,ANN) where
    -- T is the type represented by dealias(type),
    -- N is either the identifier encoded by options.name or _|_ if
       options.name does not contain a value,
    -- A is either the alignment value held by options.alignment or _|_ if
       options.alignment does not contain a value,
    -- W is either the value held by options.bit_width or _|_ if
-      options.bit_width does not contain a value, and
-   -- NUA is the value held by options.no_unique_address.
+      options.bit_width does not contain a value,
+   -- NUA is the value held by options.no_unique_address, and
+   -- ANN is the sequence of values constant_of(r) for each r in
+      options.annotations.
    Throws: meta::exception unless the following conditions are met:
    -- dealias(type) represents either an object type or a reference type;
    -- if options.name contains a value, then:
@@ -5539,15 +5562,18 @@ eval_variant_alternative (location_t loc, const 
constexpr_ctx *ctx, tree i,
         that is not a keyword when interpreted with the ordinary literal
         encoding;
    -- if options.name does not contain a value, then options.bit_width
-      contains a value;
+      contains a value and options.annotations is empty;
    -- if options.bit_width contains a value V, then
       -- is_integral_type(type) || is_enum_type(type) is true,
       -- options.alignment does not contain a value,
       -- options.no_unique_address is false,
       -- V is not negative, and
-      -- if V equals 0, then options.name does not contain a value; and
+      -- if V equals 0, then options.name does not contain a value;
    -- if options.alignment contains a value, it is an alignment value not less
-      than alignment_of(type).  */
+      than alignment_of(type); and
+   -- for every reflection r in options.annotations, has-type(r) is true,
+      type_of(r) represents a non-array object type, and evaluation of
+      constant_of(r) does not exit via an exception.  */
 
 static tree
 eval_data_member_spec (location_t loc, const constexpr_ctx *ctx,
@@ -5566,8 +5592,10 @@ eval_data_member_spec (location_t loc, const 
constexpr_ctx *ctx,
       *non_constant_p = true;
       return NULL_TREE;
     }
-  enum { m_name = 1, m_alignment, m_bit_width, m_no_unique_address, n_args };
-  tree args[n_args] = { type, NULL_TREE, NULL_TREE, NULL_TREE, NULL_TREE };
+  enum { m_name = 1, m_alignment, m_bit_width, m_no_unique_address,
+        m_annotations, n_args };
+  tree args[n_args] = { type, NULL_TREE, NULL_TREE, NULL_TREE, NULL_TREE,
+                       NULL_TREE };
   for (tree field = next_aggregate_field (TYPE_FIELDS (TREE_TYPE (opts)));
        field; field = next_aggregate_field (DECL_CHAIN (field)))
     if (tree name = DECL_NAME (field))
@@ -5580,6 +5608,8 @@ eval_data_member_spec (location_t loc, const 
constexpr_ctx *ctx,
          args[m_bit_width] = field;
        else if (id_equal (name, "no_unique_address"))
          args[m_no_unique_address] = field;
+       else if (id_equal (name, "annotations"))
+         args[m_annotations] = field;
       }
   for (int i = m_name; i < n_args; ++i)
     {
@@ -5605,6 +5635,21 @@ eval_data_member_spec (location_t loc, const 
constexpr_ctx *ctx,
            args[i] = boolean_true_node;
          continue;
        }
+      if (i == m_annotations)
+       {
+         /* To handle annotations, read it using input range from
+            std::vector<info>.  */
+         tree rtype
+           = cp_build_reference_type (TREE_TYPE (opt), /*rval*/false);
+         opt = build_address (opt);
+         opt = fold_convert (rtype, opt);
+         opt = get_info_vec (loc, ctx, opt, -1, non_constant_p, overflow_p,
+                             jump_target, fun);
+         if (*jump_target || *non_constant_p)
+           return NULL_TREE;
+         args[i] = opt;
+         continue;
+       }
       /* Otherwise the member is optional<something>.  */
       if (!CLASS_TYPE_P (TREE_TYPE (opt)))
        goto fail;
@@ -5838,6 +5883,10 @@ eval_data_member_spec (location_t loc, const 
constexpr_ctx *ctx,
     return throw_exception (loc, ctx,
                            "neither name nor bit_width specified",
                            fun, non_constant_p, jump_target);
+  if (args[m_name] == NULL_TREE && TREE_VEC_LENGTH (args[m_annotations]))
+    return throw_exception (loc, ctx,
+                           "no name and non-empty annotations specified",
+                           fun, non_constant_p, jump_target);
   if (args[m_bit_width])
     {
       if (!CP_INTEGRAL_TYPE_P (type) && TREE_CODE (type) != ENUMERAL_TYPE)
@@ -5879,17 +5928,41 @@ eval_data_member_spec (location_t loc, const 
constexpr_ctx *ctx,
                                "alignment is smaller than alignment_of",
                                fun, non_constant_p, jump_target);
     }
-  tree ret = make_tree_vec (n_args);
-  for (int i = 0; i < n_args; ++i)
+  for (int i = 0; i < TREE_VEC_LENGTH (args[m_annotations]); ++i)
+    {
+      tree r = REFLECT_EXPR_HANDLE (TREE_VEC_ELT (args[m_annotations], i));
+      reflect_kind kind
+       = REFLECT_EXPR_KIND (TREE_VEC_ELT (args[m_annotations], i));
+      if (!has_type (r, kind))
+       return throw_exception (loc, ctx, "reflection does not have a type",
+                               fun, non_constant_p, jump_target);
+      tree type = type_of (r, kind);
+      if (eval_is_array_type (loc, type) == boolean_true_node
+         || eval_is_object_type (loc, type) == boolean_false_node)
+       return throw_exception (loc, ctx, "reflection does not have "
+                                         "non-array object type",
+                               fun, non_constant_p, jump_target);
+      tree cst = eval_constant_of (loc, ctx, r, kind, non_constant_p,
+                                  overflow_p, jump_target, fun);
+      if (cst == NULL_TREE)
+       return NULL_TREE;
+      TREE_VEC_ELT (args[m_annotations], i) = cst;
+    }
+  tree ret = make_tree_vec (m_annotations
+                           + TREE_VEC_LENGTH (args[m_annotations]));
+  for (int i = 0; i < m_annotations; ++i)
     TREE_VEC_ELT (ret, i) = args[i];
+  for (int i = 0; i < TREE_VEC_LENGTH (args[m_annotations]); ++i)
+    TREE_VEC_ELT (ret, i + m_annotations)
+      = TREE_VEC_ELT (args[m_annotations], i);
   return get_reflection_raw (loc, ret, REFLECT_DATA_MEMBER_SPEC);
 }
 
 /* Process std::meta::define_aggregate.
    Let C be the type represented by class_type and r_K be the Kth reflection
    value in mdescrs.
-   For every r_K in mdescrs, let (T_K,N_K,A_K,W_K,NUA_K) be the corresponding
-   data member description represented by r_K.
+   For every r_K in mdescrs, let (T_K,N_K,A_K,W_K,NUA_K,ANN_K) be the
+   corresponding data member description represented by r_K.
    Constant When:
    -- class_type represents a cv-unqualified class type;
    -- C is incomplete from every point in the evaluation context;
@@ -5920,6 +5993,8 @@ eval_data_member_spec (location_t loc, const 
constexpr_ctx *ctx,
         Otherwise, M_K is not a bit-field.
       -- If A_K is not _|_, M_K has the alignment-specifier alignas(A_K).
         Otherwise, M_K has no alignment-specifier.
+      -- M_K has an annotation whose underlying constant is r for every
+        reflection r in ANN_K.
    -- For every r_L in mdescrs such that K<L, the declaration corresponding to
       r_K precedes the declaration corresponding to r_L.
    Returns: class_type.
@@ -6171,12 +6246,24 @@ eval_define_aggregate (location_t loc, const 
constexpr_ctx *ctx,
                              * BITS_PER_UNIT);
          DECL_USER_ALIGN (f) = 1;
        }
-      if (TREE_VEC_ELT (a, 4) == boolean_true_node)
+      if (TREE_VEC_ELT (a, 4) == boolean_true_node
+         || TREE_VEC_LENGTH (a) != 5)
        {
-         tree attr = build_tree_list (NULL_TREE,
-                                      get_identifier ("no_unique_address"));
-         attr = build_tree_list (attr, NULL_TREE);
-         cplus_decl_attributes (&f, attr, 0);
+         tree attrs = NULL_TREE, attr;
+         if (TREE_VEC_ELT (a, 4) == boolean_true_node)
+           {
+             attr = build_tree_list (NULL_TREE,
+                                     get_identifier ("no_unique_address"));
+             attrs = build_tree_list (attr, NULL_TREE);
+           }
+         for (int i = TREE_VEC_LENGTH (a) - 1; i >= 5; --i)
+           {
+             attr = build_tree_list (internal_identifier,
+                                     annotation_identifier);
+             tree val = REFLECT_EXPR_HANDLE (TREE_VEC_ELT (a, i));
+             attrs = tree_cons (attr, build_tree_list (NULL_TREE, val), attrs);
+           }
+         cplus_decl_attributes (&f, attrs, 0);
        }
       fields = f;
     }
@@ -8443,13 +8530,24 @@ compare_reflections (tree lhs, tree rhs)
       rhs = maybe_update_function_parm (rhs);
     }
   else if (lkind == REFLECT_DATA_MEMBER_SPEC)
-    return (TREE_VEC_ELT (lhs, 0) == TREE_VEC_ELT (rhs, 0)
-           && TREE_VEC_ELT (lhs, 1) == TREE_VEC_ELT (rhs, 1)
-           && tree_int_cst_equal (TREE_VEC_ELT (lhs, 2),
-                                  TREE_VEC_ELT (rhs, 2))
-           && tree_int_cst_equal (TREE_VEC_ELT (lhs, 3),
-                                  TREE_VEC_ELT (rhs, 3))
-           && TREE_VEC_ELT (lhs, 4) == TREE_VEC_ELT (rhs, 4));
+    {
+      if (typedef_variant_p (TREE_VEC_ELT (lhs, 0))
+         != typedef_variant_p (TREE_VEC_ELT (rhs, 0))
+         || !same_type_p (TREE_VEC_ELT (lhs, 0), TREE_VEC_ELT (rhs, 0))
+         || TREE_VEC_ELT (lhs, 1) != TREE_VEC_ELT (rhs, 1)
+         || !tree_int_cst_equal (TREE_VEC_ELT (lhs, 2),
+                                 TREE_VEC_ELT (rhs, 2))
+         || !tree_int_cst_equal (TREE_VEC_ELT (lhs, 3),
+                                 TREE_VEC_ELT (rhs, 3))
+         || TREE_VEC_ELT (lhs, 4) != TREE_VEC_ELT (rhs, 4)
+         || TREE_VEC_LENGTH (lhs) != TREE_VEC_LENGTH (rhs))
+       return false;
+      for (int i = 5; i < TREE_VEC_LENGTH (lhs); ++i)
+       if (!compare_reflections (TREE_VEC_ELT (lhs, i),
+                                 TREE_VEC_ELT (rhs, i)))
+         return false;
+      return true;
+    }
   else if (lkind == REFLECT_ANNOTATION)
     return TREE_VALUE (lhs) == TREE_VALUE (rhs);
   else if (TYPE_P (lhs) && TYPE_P (rhs))
diff --git a/gcc/testsuite/g++.dg/reflect/data_member_spec5.C 
b/gcc/testsuite/g++.dg/reflect/data_member_spec5.C
new file mode 100644
index 000000000000..3430cc0da1d2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/reflect/data_member_spec5.C
@@ -0,0 +1,114 @@
+// { dg-do compile { target c++26 } }
+// { dg-additional-options "-freflection" }
+// Test std::meta::data_member_spec.
+
+#include <meta>
+
+using namespace std::meta;
+
+consteval bool
+valid_data_member_spec (info type, data_member_options opts)
+{
+  try { data_member_spec (type, opts); }
+  catch (std::meta::exception &) { return false; }
+  return true;
+}
+
+struct S { int a, b; };
+
+consteval bool
+foo ()
+{
+  constexpr int two = 2;
+  [[=1]] int three = 3;
+  constexpr int fourtytwo = 42;
+  constexpr double fourtytwoandhalf = 42.5;
+  data_member_options a = { .name = "_",
+                           .annotations = { ^^two, reflect_constant (42),
+                                            annotations_of (^^three)[0],
+                                            reflect_constant (42.5),
+                                            reflect_constant (S { 1, 2 }) } };
+  auto dmsa = data_member_spec (^^int, a);
+  if (!is_data_member_spec (dmsa))
+    throw 1;
+  if (dmsa
+      != data_member_spec (^^int,
+                          { .name = "_",
+                            .annotations = { reflect_constant (2),
+                                             ^^fourtytwo,
+                                             reflect_constant (1),
+                                             ^^fourtytwoandhalf,
+                                             reflect_constant (S { 1, 2 }) } 
}))
+    throw 2;
+  if (dmsa == data_member_spec (^^int, { .name = "_" }))
+    throw 3;
+  if (dmsa
+      == data_member_spec (^^int,
+                          { .name = "_",
+                            .annotations = { reflect_constant (2L),
+                                             ^^fourtytwo,
+                                             reflect_constant (1),
+                                             ^^fourtytwoandhalf,
+                                             reflect_constant (S { 1, 2 }) } 
}))
+    throw 4;
+  if (dmsa
+      == data_member_spec (^^int,
+                          { .name = "_",
+                            .annotations = { reflect_constant (2),
+                                             ^^two,
+                                             reflect_constant (1),
+                                             ^^fourtytwoandhalf,
+                                             reflect_constant (S { 1, 2 }) } 
}))
+    throw 4;
+  if (dmsa
+      == data_member_spec (^^int,
+                          { .name = "_",
+                            .annotations = { reflect_constant (2),
+                                             ^^fourtytwo,
+                                             reflect_constant (3),
+                                             ^^fourtytwoandhalf,
+                                             reflect_constant (S { 1, 2 }) } 
}))
+    throw 5;
+  if (dmsa
+      == data_member_spec (^^int,
+                          { .name = "_",
+                            .annotations = { reflect_constant (2),
+                                             ^^fourtytwo,
+                                             reflect_constant (1),
+                                             reflect_constant (42.25),
+                                             reflect_constant (S { 1, 2 }) } 
}))
+    throw 6;
+  if (dmsa
+      == data_member_spec (^^int,
+                          { .name = "_",
+                            .annotations = { reflect_constant (2),
+                                             ^^fourtytwo,
+                                             reflect_constant (1),
+                                             reflect_constant (42.25),
+                                             reflect_constant (S { 1, 2 }) } 
}))
+    throw 7;
+  if (dmsa
+      == data_member_spec (^^int,
+                          { .name = "_",
+                            .annotations = { reflect_constant (2),
+                                             ^^fourtytwo,
+                                             reflect_constant (1),
+                                             reflect_constant (42.5),
+                                             reflect_constant (S { 2, 2 }) } 
}))
+    throw 8;
+  return true;
+}
+
+static_assert (foo ());
+
+constexpr int arr[1] = { 1 };
+constexpr int i = 42;
+constexpr S s = { 42, 43 };
+
+static_assert (!valid_data_member_spec (^^int, { .name = "a", .annotations = { 
^^:: } }));
+static_assert (!valid_data_member_spec (^^int, { .name = "a", .annotations = { 
^^foo } }));
+static_assert (!valid_data_member_spec (^^int, { .name = "a", .annotations = { 
^^arr } }));
+static_assert (!valid_data_member_spec (^^int, { .name = "a", .annotations = { 
^^arr } }));
+static_assert (valid_data_member_spec (^^int, { .name = "a", .annotations = { 
^^i } }));
+static_assert (valid_data_member_spec (^^int, { .name = "a", .annotations = { 
^^s } }));
+static_assert (!valid_data_member_spec (^^int, { .bit_width = 0, .annotations 
= { ^^i } }));
diff --git a/gcc/testsuite/g++.dg/reflect/data_member_spec6.C 
b/gcc/testsuite/g++.dg/reflect/data_member_spec6.C
new file mode 100644
index 000000000000..5b53fb4b5337
--- /dev/null
+++ b/gcc/testsuite/g++.dg/reflect/data_member_spec6.C
@@ -0,0 +1,12 @@
+// { dg-do compile { target c++26 } }
+// { dg-additional-options "-freflection" }
+// Test std::meta::data_member_spec.
+
+#include <meta>
+
+using namespace std::meta;
+
+struct T { constexpr T () : t (42) {} constexpr int bar () const { return t; } 
protected: int t; };
+constexpr T t;
+
+constexpr auto a = data_member_spec (^^int, { .name = "a", .annotations = { 
^^t } }); // { dg-error "'T' must be a cv-unqualified structural type that is 
not a reference type" }
diff --git a/gcc/testsuite/g++.dg/reflect/define_aggregate9.C 
b/gcc/testsuite/g++.dg/reflect/define_aggregate9.C
new file mode 100644
index 000000000000..143ce68f4f3c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/reflect/define_aggregate9.C
@@ -0,0 +1,35 @@
+// { dg-do compile { target c++26 } }
+// { dg-additional-options "-freflection" }
+// Test std::meta::define_aggregate.
+
+#include <meta>
+
+using namespace std::meta;
+
+struct S { int a, b; };
+struct T;
+
+consteval
+{
+  constexpr int two = 2;
+  [[=1]] int three = 3;
+  constexpr int fourtytwo = 42;
+  constexpr double fourtytwoandhalf = 42.5;
+  data_member_options a = { .name = "_",
+                           .annotations = { ^^two, reflect_constant (42),
+                                            annotations_of (^^three)[0],
+                                            reflect_constant (42.5),
+                                            reflect_constant (S { 1, 2 }) } };
+  auto dmsa = data_member_spec (^^int, a);
+  define_aggregate (^^T, { dmsa });
+}
+consteval
+{
+  static_assert (annotations_of (^^T::_).size () == 5);
+  static_assert ([: constant_of (annotations_of (^^T::_)[0]) :] == 2);
+  static_assert ([: constant_of (annotations_of (^^T::_)[1]) :] == 42);
+  static_assert ([: constant_of (annotations_of (^^T::_)[2]) :] == 1);
+  static_assert ([: constant_of (annotations_of (^^T::_)[3]) :] == 42.5);
+  static_assert ([: constant_of (annotations_of (^^T::_)[4]) :].a == 1);
+  static_assert ([: constant_of (annotations_of (^^T::_)[4]) :].b == 2);
+}
diff --git a/gcc/testsuite/g++.dg/reflect/display_string_of1.C 
b/gcc/testsuite/g++.dg/reflect/display_string_of1.C
index b2f2950a5397..ae24aff1e9d2 100644
--- a/gcc/testsuite/g++.dg/reflect/display_string_of1.C
+++ b/gcc/testsuite/g++.dg/reflect/display_string_of1.C
@@ -115,10 +115,11 @@ foo (int a, const long b, T c, int d[4], T &e)
   static_assert (display_string_of (^^NSAlias) == "NSAlias");
   static_assert (display_string_of (^^NS) == "NS");
   static_assert (display_string_of (bases_of (^^S, ctx)[0]) == "S: B");
-  static_assert (display_string_of (data_member_spec (^^int, { .name = 
"member", .alignment = 128, .no_unique_address = true })) == "(int, member, 
128, , true)");
-  static_assert (display_string_of (data_member_spec (^^const int, { .name = 
"member", .bit_width = 6 })) == "(const int, member, , 6, false)");
-  static_assert (display_string_of (data_member_spec (^^int, { .bit_width = 0 
})) == "(int, , , 0, false)");
-  static_assert (display_string_of (data_member_spec (^^long, { .bit_width = 5 
})) == "(long int, , , 5, false)");
+  static_assert (display_string_of (data_member_spec (^^int, { .name = 
"member", .alignment = 128, .no_unique_address = true })) == "(int, member, 
128, , true, {})");
+  static_assert (display_string_of (data_member_spec (^^const int, { .name = 
"member", .bit_width = 6 })) == "(const int, member, , 6, false, {})");
+  static_assert (display_string_of (data_member_spec (^^int, { .bit_width = 0 
})) == "(int, , , 0, false, {})");
+  static_assert (display_string_of (data_member_spec (^^long, { .bit_width = 5 
})) == "(long int, , , 5, false, {})");
+  static_assert (display_string_of (data_member_spec (^^int, { .name = "_", 
.annotations = { reflect_constant (42), reflect_constant (42.5) }})) == "(int, 
_, , , false, {42, 4.25e+1})");
   static_assert (display_string_of (annotations_of (^^bar)[0]) == "[[=1]]");
   static_assert (display_string_of (annotations_of (^^bar)[1]) == "[[=AN{1, 
42, ' '}]]");
   static_assert (display_string_of (^^int) == "int");
diff --git a/gcc/testsuite/g++.dg/reflect/mangle1.C 
b/gcc/testsuite/g++.dg/reflect/mangle1.C
index 92b4ec31c735..16e027d4b3dd 100644
--- a/gcc/testsuite/g++.dg/reflect/mangle1.C
+++ b/gcc/testsuite/g++.dg/reflect/mangle1.C
@@ -63,6 +63,7 @@ namespace NS2 {
   };
   struct Z {
   };
+  struct AA { int a, b; };
 }
 
 constexpr auto ctx = std::meta::access_context::current ();
@@ -165,6 +166,11 @@ baz (int x)
   bar <332, data_member_spec (^^unsigned short, { .name = "b", .bit_width = 5 
})> (); // data member description
   bar <333, data_member_spec (^^long, { .bit_width = 3 })> (); // data member 
description
   bar <334, data_member_spec (^^int, { .bit_width = 0 })> (); // data member 
description
+  bar <335, std::meta::data_member_spec (^^int,
+                                        { .name = "_",
+                                          .annotations = { 
std::meta::reflect_constant (42),
+                                                           
std::meta::reflect_constant (43L),
+                                                           
std::meta::reflect_constant (NS2::AA { 1, 2 }) } })> (); // data member 
description
   bar <340, ^^NS2::X::~X> (); // function
 }
 
@@ -250,4 +256,5 @@ baz (int x)
 // { dg-final { scan-assembler "_Z3barILi332ELDmdst_1b__5_EEvv" } }
 // { dg-final { scan-assembler "_Z3barILi333ELDmdsl___3_EEvv" } }
 // { dg-final { scan-assembler "_Z3barILi334ELDmdsi___0_EEvv" } }
+// { dg-final { scan-assembler 
"_Z3barILi335ELDmdsi_1____Li42ELl43EXtlN3NS22AAELi1ELi2EEEEEvv" } }
 // { dg-final { scan-assembler "_Z3barILi340ELDmfnN3NS21XD4EvEEvv" } }
diff --git a/gcc/testsuite/g++.dg/reflect/u8display_string_of1.C 
b/gcc/testsuite/g++.dg/reflect/u8display_string_of1.C
index bce7db52a176..0ff9cc7c992d 100644
--- a/gcc/testsuite/g++.dg/reflect/u8display_string_of1.C
+++ b/gcc/testsuite/g++.dg/reflect/u8display_string_of1.C
@@ -115,10 +115,11 @@ foo (int a, const long b, T c, int d[4], T &e)
   static_assert (u8display_string_of (^^NSAlias) == u8"NSAlias");
   static_assert (u8display_string_of (^^NS) == u8"NS");
   static_assert (u8display_string_of (bases_of (^^S, ctx)[0]) == u8"S: B");
-  static_assert (u8display_string_of (data_member_spec (^^int, { .name = 
"member", .alignment = 128, .no_unique_address = true })) == u8"(int, member, 
128, , true)");
-  static_assert (u8display_string_of (data_member_spec (^^const int, { .name = 
"member", .bit_width = 6 })) == u8"(const int, member, , 6, false)");
-  static_assert (u8display_string_of (data_member_spec (^^int, { .bit_width = 
0 })) == u8"(int, , , 0, false)");
-  static_assert (u8display_string_of (data_member_spec (^^long, { .bit_width = 
5 })) == u8"(long int, , , 5, false)");
+  static_assert (u8display_string_of (data_member_spec (^^int, { .name = 
"member", .alignment = 128, .no_unique_address = true })) == u8"(int, member, 
128, , true, {})");
+  static_assert (u8display_string_of (data_member_spec (^^const int, { .name = 
"member", .bit_width = 6 })) == u8"(const int, member, , 6, false, {})");
+  static_assert (u8display_string_of (data_member_spec (^^int, { .bit_width = 
0 })) == u8"(int, , , 0, false, {})");
+  static_assert (u8display_string_of (data_member_spec (^^long, { .bit_width = 
5 })) == u8"(long int, , , 5, false, {})");
+  static_assert (u8display_string_of (data_member_spec (^^int, { .name = 
u8"_", .annotations = { reflect_constant (42), reflect_constant (42.5) }})) == 
u8"(int, _, , , false, {42, 4.25e+1})");
   static_assert (u8display_string_of (annotations_of (^^bar)[0]) == 
u8"[[=1]]");
   static_assert (u8display_string_of (annotations_of (^^bar)[1]) == 
u8"[[=AN{1, 42, ' '}]]");
   static_assert (u8display_string_of (^^int) == u8"int");
diff --git a/libstdc++-v3/include/std/meta b/libstdc++-v3/include/std/meta
index 4e438e8b6536..20cfba10b9f9 100644
--- a/libstdc++-v3/include/std/meta
+++ b/libstdc++-v3/include/std/meta
@@ -427,6 +427,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       optional<int> alignment;
       optional<int> bit_width;
       bool no_unique_address = false;
+      vector<info> annotations;
     };
     consteval info data_member_spec(info, data_member_options);
     consteval bool is_data_member_spec(info);

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