https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117289
--- Comment #2 from Indu Bhagat <ibhagat at gcc dot gnu.org> ---
Regarding handling of duplicate types in CTF, the bulk of expectation lies on
the link-time de-duplication. On the compiler side, we simply try to not emit
duplicate CTF types to avoid bloating up the object files (and well, to reduce
the work at link time): this is achieved by DWARF DIE references as the key in
the ctfc_types hash_table (see ctf_type_exists ()).
In this testcase, when -std=gnu23 is added to the command line, I do see that
there are two distinct DWARF DIEs with tag DW_TAG_subroutine_type: one for the
structure member and another for the typedef. (As a consequence, we see the two
CTF types are added in the CTF container).
<2><3c>: Abbrev Number: 2 (DW_TAG_member)
<3d> DW_AT_name : (indirect string, offset: 0x6f7): func
<41> DW_AT_decl_file : 1
<41> DW_AT_decl_line : 14
<42> DW_AT_decl_column : 16
<43> DW_AT_type : <0x59>
<47> DW_AT_data_member_location: 8
<2><48>: Abbrev Number: 0
<1><49>: Abbrev Number: 1 (DW_TAG_pointer_type)
<4a> DW_AT_byte_size : 8
<4a> DW_AT_type : <0x22>
<1><4e>: Abbrev Number: 3 (DW_TAG_subroutine_type)
<4f> DW_AT_prototyped : 1
<4f> DW_AT_sibling : <0x59>
<2><53>: Abbrev Number: 4 (DW_TAG_formal_parameter)
<54> DW_AT_type : <0x49>
<2><58>: Abbrev Number: 0
<1><59>: Abbrev Number: 1 (DW_TAG_pointer_type)
<5a> DW_AT_byte_size : 8
<5a> DW_AT_type : <0x4e>
...
<1><74>: Abbrev Number: 8 (DW_TAG_typedef)
<75> DW_AT_name : (indirect string, offset: 0x227c):
rcu_callback_t
<79> DW_AT_decl_file : 1
<7a> DW_AT_decl_line : 20
<7b> DW_AT_decl_column : 16
<7c> DW_AT_type : <0x80>
<1><80>: Abbrev Number: 1 (DW_TAG_pointer_type)
<81> DW_AT_byte_size : 8
<81> DW_AT_type : <0x85>
<1><85>: Abbrev Number: 3 (DW_TAG_subroutine_type)
<86> DW_AT_prototyped : 1
<86> DW_AT_sibling : <0x90>
<2><8a>: Abbrev Number: 4 (DW_TAG_formal_parameter)
<8b> DW_AT_type : <0x49>
<2><8f>: Abbrev Number: 0
<1><90>: Abbrev Number: 9 (DW_TAG_variable)
<91> DW_AT_name : rcb
<95> DW_AT_decl_file : 1
<96> DW_AT_decl_line : 22
<97> DW_AT_decl_column : 16
<98> DW_AT_type : <0x74>
<9c> DW_AT_external : 1
<9c> DW_AT_location : 9 byte block: 3 10 0 0 0 0 0 0 0
(DW_OP_addr: 10)
