https://gcc.gnu.org/bugzilla/show_bug.cgi?id=128061
Bug ID: 128061
Summary: [DebugInfo] Zero-length inline DIE without abstract
origin emitted for a TLS wrapper
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
Assignee: unassigned at gcc dot gnu.org
Reporter: wujielun402 at gmail dot com
Target Milestone: ---
With -O2 -g -gdwarf-5, GCC emits a zero-length DW_TAG_inlined_subroutine
inside read_cell for a compiler-generated C++ thread-local storage (TLS)
wrapper. The entry records an inline entry point and call-site coordinates,
but has neither DW_AT_abstract_origin nor a name identifying the inlined
function. Is this entry intentional for inline-entry tracking, or should
it be omitted or given an abstract-origin reference?
Reproducer source (repro.cc):
int make_value ();
struct cell_type
{
cell_type ();
int value;
};
cell_type::cell_type () : value (make_value ()) {}
thread_local cell_type cell;
int
read_cell ()
{
return cell.value;
}
Compile to an object:
g++ -O2 -g -gdwarf-5 -c repro.cc -o repro.o
Compiler Explorer: https://godbolt.org/z/x6dG7PMs9
Relevant excerpt from the supplied readelf .debug_info output:
<2><cd>: Abbrev Number: 17 (DW_TAG_inlined_subroutine)
<ce> DW_AT_entry_pc : 0x10
<d6> DW_AT_GNU_entry_view: 2
<d7> DW_AT_low_pc : 0x10
<df> DW_AT_high_pc : 0
<e7> DW_AT_call_file : 1
<e8> DW_AT_call_line : 15
<e9> DW_AT_call_column : 11
<2><ea>: Abbrev Number: 2 (DW_TAG_inlined_subroutine)
<eb> DW_AT_abstract_origin: <0xa1>
DW_AT_high_pc is a length here, so DIE 0xcd covers the empty range
[0x10, 0x10). It has no children and no DW_AT_name, DW_AT_linkage_name,
DW_AT_specification, or DW_AT_abstract_origin. DIE 0xea is a separate
sibling entry, not a source of inherited attributes for DIE 0xcd.
Source inspection suggests a mismatch between ignoring the wrapper's
function description and retaining its inline-instance description:
get_tls_wrapper_fn in gcc/cp/decl2.cc marks the wrapper DECL_IGNORED_P,
while gen_inlined_subroutine_die in gcc/dwarf2out.cc still creates the
inline DIE. add_abstract_origin_attribute adds no reference when the
origin DIE is absent.
