https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122496
--- Comment #1 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Qing Zhao <[email protected]>: https://gcc.gnu.org/g:aa27219f9abdd8030fa38aae64c3a4d1231c73e8 commit r16-6784-gaa27219f9abdd8030fa38aae64c3a4d1231c73e8 Author: Qing Zhao <[email protected]> Date: Wed Jan 14 17:14:01 2026 +0000 C: fix issues when supporting counted_by fields in anonymous structure/unions [PR122495,PR122496] Currently, GCC does not fully support the cases when a FAM or pointer field and its corresponding counted_by field are in different anonymous structure/unions of a common named structure. For example: struct nested_mixed { struct { union { int b; float f; }; int n; }; struct { PTR_TYPE *pointer __attribute__((__counted_by__(n))); FAM_TYPE c[] __attribute__((__counted_by__(b))); }; } *nested_mixed_annotated; In order to support such cases, we always need to locate the first outer named structure as the root, and then lookup_field inside this named structure. When building the component_ref for the counted_by field, we need to build a chain of component_ref starting from the root structure. When supporting the above in general, we also need to handle the following several special cases correctly: A. Support an untagged type as its own top-level type. */ struct { int a; char b[] __attribute__ ((counted_by (a))); } *x; B. Support an unnamed field with a named struct/union. */ struct s { struct { int a; char b[] __attribute__ ((counted_by (a))); } *x; } *y; C. When -fms-extensions is enabled: C.1 Do not support the inward-to-outward counted-by field reference since checking the validity of such reference depends on unknown situation at the end of the structure definition. struct bar { char *buf __counted_by (n); /* { dg-error "attribute is not a field declaration in the same structure as" } */ }; C.2 support the outward-to-inward counted-by field reference. PR C/122495 PR C/122496 gcc/c/ChangeLog: * c-decl.cc (grokfield): Call verify_counted_by_for_top_anonymous_type for named field. (verify_counted_by_attribute): Change the prototype to a recursive routine. (verify_counted_by_for_top_anonymous_type): New routine. (finish_struct): Set C_TYPE_FIELDS_HAS_COUNTED_BY and call the routine verify_counted_by_attribute only for named structure. * c-parser.cc (c_parser_declaration_or_fndef): Call verify_counted_by_for_top_anonymous_type for the decl. (c_parser_parameter_declaration): Call verify_counted_by_for_top_anonymous_type for the parameter. (c_parser_type_name): Call verify_counted_by_for_top_anonymous_type for the type. * c-tree.h (C_TYPE_FIELDS_HAS_COUNTED_BY): New flag. (verify_counted_by_for_top_anonymous_type): New routine. * c-typeck.cc (build_counted_by_ref): Locate the root named structure, build a chain of component_ref starting from the root structure. gcc/testsuite/ChangeLog: * gcc.dg/counted-by-anonymous-2-char.c: New test. * gcc.dg/counted-by-anonymous-2-float.c: New test. * gcc.dg/counted-by-anonymous-2-struct.c: New test. * gcc.dg/counted-by-anonymous-2-union.c: New test. * gcc.dg/counted-by-anonymous-2.c: New test. * gcc.dg/counted-by-anonymous-3.c: New test. * gcc.dg/counted-by-anonymous.c: New test. * gcc.dg/ubsan/counted-by-anonymous-bounds-1.c: New test. * gcc.dg/ubsan/counted-by-anonymous-bounds-2.c: New test. * gcc.dg/ubsan/counted-by-anonymous-bounds.c: New test.
