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This PR reveals that cxx_eval_bare_aggregate and cxx_eval_store_expression do not anticipate that a constructor element's initializer could mutate the underlying CONSTRUCTOR. Evaluation of the initializer could add new elements to the underlying CONSTRUCTOR, thereby potentially invalidating any pointers to or assumptions about the CONSTRUCTOR's elements, and so these routines should be prepared for that. To fix this problem, this patch makes cxx_eval_bare_aggregate and cxx_eval_store_expression recompute the constructor_elt pointers through which we're assigning, after it evaluates the initializer. Care is taken to to not slow down the common case where the initializer does not modify the underlying CONSTRUCTOR. gcc/cp/ChangeLog: PR c++/94219 PR c++/94205 * constexpr.c (get_or_insert_ctor_field): Split out (while adding support for VECTOR_TYPEs, and optimizations for the common case) from ... (cxx_eval_store_expression): ... here. Rename local variable 'changed_active_union_member_p' to 'activated_union_member_p'. Record the sequence of indexes into 'indexes' that yields the subobject we're assigning to. Record the integer offsets of the constructor indexes we're assigning through into 'index_pos_hints'. After evaluating the initializer of the store expression, recompute 'valp' using 'indexes' and using 'index_pos_hints' as hints. (cxx_eval_bare_aggregate): Tweak comments. Use get_or_insert_ctor_field to recompute the constructor_elt pointer we're assigning through after evaluating each initializer. gcc/testsuite/ChangeLog: PR c++/94219 PR c++/94205 * g++.dg/cpp1y/constexpr-nsdmi3.C: New test. * g++.dg/cpp1y/constexpr-nsdmi4.C: New test. * g++.dg/cpp1y/constexpr-nsdmi5.C: New test. * g++.dg/cpp1z/lambda-this5.C: New test.
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