https://sourceware.org/bugzilla/show_bug.cgi?id=29451
--- Comment #4 from Sergei Trofimovich <slyich at gmail dot com> --- (In reply to Nick Clifton from comment #3) > (In reply to Sergei Trofimovich from comment #0) > > > <28> DW_AT_low_pc : (addr) 0x0 > > <2c> DW_AT_high_pc : (addr) 0x0 > > > Would it be fair to say it's a bug to assign zero size here via DW_AT_low_pc > > / DW_AT_high_pc? > > Actually it *is* fair to give them 0 values. (The values are addresses, not > sizes). The reason is that the address of the start and end of the > __x86.get_pc_thunk.bx function has not been assigned yet. (This is an > object file, not a fully linked executable). > > If you look at the relocations for the crti.o file you find: > > Relocation section '.rel.debug_info' at offset 0x288 contains 12 entries: > Offset Info Type Sym. Value Symbol's Name > [...] > 00000036 00000901 R_386_32 00000000 __x86.get_pc_thunk.bx > 0000003a 00000901 R_386_32 00000000 __x86.get_pc_thunk.bx > > So when this file is linked in with object files and these relocations are > resolved the correct values for the __x86.get_pc_thunk.bx symbol will be > installed into the .debug_info section, and everything should work. In https://sourceware.org/PR29450 we observed zero-size on a final executable. Is zero a reasonable value here? `__x86.get_pc_thunk.bx` lives in a separate section compared to `_init`. Nick, are you sure you are looking at the `_init` debug relocations and not `__x86.get_pc_thunk.bx`? I think both are present and are slightly different. Looking at the specific offsets: $ readelf -aW --debug-dump crti.o ... Contents of the .debug_info section: Compilation Unit @ offset 0x0: Length: 0x3b (32-bit) Version: 2 Abbrev Offset: 0x0 Pointer Size: 4 <0><b>: Abbrev Number: 1 (DW_TAG_compile_unit) <c> DW_AT_stmt_list : (data4) 0x0 <10> DW_AT_ranges : (data4) 0x0 <14> DW_AT_name : (strp) (offset: 0x0): crti.S.S <18> DW_AT_comp_dir : (strp) (offset: 0x9): /tmp <1c> DW_AT_producer : (strp) (offset: 0xe): GNU AS 2.39 <20> DW_AT_language : (data2) 32769 (MIPS assembler) <1><22>: Abbrev Number: 2 (DW_TAG_subprogram) <23> DW_AT_name : (strp) (offset: 0x1a): _init <27> DW_AT_external : (flag) 1 <28> DW_AT_low_pc : (addr) 0x0 ; <<<--- <2c> DW_AT_high_pc : (addr) 0x0 ; <<<--- ... The concern is `DW_AT_low_pc / DW_AT_high_pc` at 0x28/0xac. $ objdump -Dr crti.o 00000000 <.debug_info>: ... 26: 00 01 add %al,(%ecx) ... 28: R_386_32 _init ; <<<--- 2c: R_386_32 _init ; <<<--- 30: 02 20 add (%eax),%ah These are DW_AT_low_pc=_init, DW_AT_high_pc=_init. AFAIU DW_AT_high_pc should be somehting like _init+2 to at least account for `ud2`. -- You are receiving this mail because: You are on the CC list for the bug.
