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Re: Query about DWARF output for recursively nested inlined subroutines
- From: Michael Eager <eager at eagerm dot com>
- To: Dan Towner <dant at picochip dot com>
- Cc: gcc at gcc dot gnu dot org, DWARF <dwarf-discuss at lists dot dwarfstd dot org>
- Date: Fri, 02 Mar 2012 11:00:32 -0800
- Subject: Re: Query about DWARF output for recursively nested inlined subroutines
- References: <a8981556839563b263f89f08b7836e60.squirrel@mail.picochip.co.uk>
On 03/02/2012 02:49 AM, Dan Towner wrote:
Hi all,
I have noticed the following construct appearing in some DWARF output and
I'm don't understand what it means, or whether it is actually a bug:
.uleb128 0x1c ;# (DIE (0x80a) DW_TAG_inlined_subroutine)
.long 0x635 ;# DW_AT_abstract_origin
.word _picoMark_LBB23 ;# DW_AT_low_pc
.word _picoMark_LBE23 ;# DW_AT_high_pc
.byte 0x1 ;# DW_AT_call_file
(/home/dant/Tools/Verification/Flow/standalone_fn_error.vhd)
.byte 0xaf ;# DW_AT_call_line
.uleb128 0x17 ;# (DIE (0x815) DW_TAG_formal_parameter)
.long 0x650 ;# DW_AT_abstract_origin
.long _picoMark_LLST15 ;# DW_AT_location
.uleb128 0x1c ;# (DIE (0x81e) DW_TAG_inlined_subroutine)
.long 0x635 ;# DW_AT_abstract_origin
.word _picoMark_LBB25 ;# DW_AT_low_pc
.word _picoMark_LBE25 ;# DW_AT_high_pc
.byte 0x1 ;# DW_AT_call_file
(/home/dant/Tools/Verification/Flow/standalone_fn_error.vhd)
.byte 0x47 ;# DW_AT_call_line
.uleb128 0x17 ;# (DIE (0x829) DW_TAG_formal_parameter)
.long 0x650 ;# DW_AT_abstract_origin
.long _picoMark_LLST16 ;# DW_AT_location
.uleb128 0x1e ;# (DIE (0x832) DW_TAG_lexical_block)
.word _picoMark_LBB26 ;# DW_AT_low_pc
.word _picoMark_LBE26 ;# DW_AT_high_pc
There are two puzzling things about this little fragment. Firstly the
inlined subroutine contains another inline instance of the same subroutine
within itself (i.e., the first inlined subroutine has abstract origin
0x635, and it contains another inlined subroutine child with the same
abstract origin). This seems to imply that the subroutine is recursive,
which it isn't. Nowhere in the source code does the subroutine call
itself.
>
Secondly, the DWARF contains call site information for the two
subroutines, but the second one is simply wrong. The source line for the
supposed call site (0x47 above) is the first line of the definition of
`main', and isn't even a call site.
I can supply a test case (for the picochip port) if necessary, but I just
wanted to get an idea of whether this really is a problem, or I'm just
misinterpreting what is going on.
It's a bit difficult to tell what is going on.
Can you post a small program which creates output like this,
along with output from readelf -w or dwarfdump?
--
Michael Eager eager@eagercon.com
1960 Park Blvd., Palo Alto, CA 94306 650-325-8077