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Re: gas -Werror compilation break [Re: [patch ld bfd gas]: Handle linkonce for cfi generated debug_frame and eh_frame data]
- From: Kai Tietz <ktietz at redhat dot com>
- To: Dave Korn <dave dot korn dot cygwin at gmail dot com>
- Cc: Nick Clifton <nickc at redhat dot com>, Kai Tietz <ktietz70 at googlemail dot com>, "H.J. Lu" <hjl dot tools at gmail dot com>, Binutils <binutils at sourceware dot org>, Alan Modra <amodra at gmail dot com>, Jan Kratochvil <jan dot kratochvil at redhat dot com>
- Date: Thu, 5 May 2011 04:49:54 -0400 (EDT)
- Subject: Re: gas -Werror compilation break [Re: [patch ld bfd gas]: Handle linkonce for cfi generated debug_frame and eh_frame data]
----- Original Message -----
From: "Dave Korn" <dave.korn.cygwin@gmail.com>
To: "Jan Kratochvil" <jan.kratochvil@redhat.com>
Cc: "Kai Tietz" <ktietz@redhat.com>, "Nick Clifton" <nickc@redhat.com>, "Kai Tietz" <ktietz70@googlemail.com>, "H.J. Lu" <hjl.tools@gmail.com>, "Binutils" <binutils@sourceware.org>, "Alan Modra" <amodra@gmail.com>
Sent: Thursday, May 5, 2011 2:29:20 AM
Subject: Re: gas -Werror compilation break [Re: [patch ld bfd gas]: Handle linkonce for cfi generated debug_frame and eh_frame data]
On 27/04/2011 21:34, Jan Kratochvil wrote:
> Hi Kai,
>
> On Tue, 26 Apr 2011 17:30:08 +0200, Nick Clifton wrote:
>>>>> ChangeLog gas/
>>>>> 2011-04-18 Kai Tietz
>>>>>
>>>>> * dw2gencfi.c (dwcfi_seg_list): New struct.
>>>>> (dwcfi_hash): New static hash variable.
>>>>> (get_debugseg_name): New.
>>>>> (alloc_debugseg_item): New.
>>>>> (make_debug_seg): New.
>>>>> (dwcfi_hash_insert): New.
>>>>> (dwcfi_hash_find): New.
>>>>> (dwcfi_hash_find_or_make): New.
>>>>> (cfi_insn_data): New member cur_seg.
>>>>> (cie_entry): Likewise.
>>>>> (fde_entry): New cseg and handled members.
>>>>> (alloc_fde_entry): Initialize cseg member.
>>>>> (alloc_cfi_insn_data): Initialize cur_seg member.
>>>>> (dot_cfi_sections): Compare for beginning of
>>>>> section names via strncmp.
>>>>> (get_cfi_seg): New.
>>>>> (cfi_finish): Treat link-once sections.
>>>>> (is_now_linkonce_segment): New local helper.
>>>>> (output_cie): Ignore cie entries not member of current
>>>>> segment.
>>>>> (output_fde): Likewise.
>>>>> (select_cie_for_fde): Likewise.
>>>>> (cfi_change_reg_numbers): Add new argument for current segment
>>>>> and ignore insn elements, if not part of current segment.
>>>>> * ehopt.c (get_cie_info): Use strncmp for
>>>>> section name matching.
>>>>> (heck_eh_frame): Likewise.
>
> dw2gencfi.c:1870:8: error: variable âcfi_segâ set but not used [-Werror=unused-but-set-variable]
> gcc-4.6.0-5.fc15.x86_64
>
> Could you please provide a fix?
This fixes the breakage, but doesn't address the issue that it looks to me
like there's an omitted call to md_fix_up_eh_frame() after the second
invocation of get_cfi_seg().
gas/ChangeLog:
* dw2gencfi.c (dwcfi_hash): Wrap in #ifdef md_fix_up_eh_frame.
(get_debugseg_name): Likewise.
(alloc_debugseg_item): Likewise.
(make_debug_seg): Likewise.
(dwcfi_hash_insert): Likewise.
(dwcfi_hash_find): Likewise.
(dwcfi_hash_find_or_make): Likewise.
(get_cfi_seg): Likewise.
(cfi_finish): Wrap references to cfi_seg and calls to get_cfi_seg()
in #ifdef md_fix_up_eh_frame likewise.
Verified that it fixes the build on i686-pc-cygwin and
x86_64-unknown-linux-gnu, OK to install?
cheers,
DaveK
Hmm, I see the issue that cfi_seg might be just set, but not used. This can be fixed by simply adding - after setting of cfi_seg - an check for if (!cfi_seg) abort ();. This check is superflous as cfi_seg never can be NULL, but it silence this warning.
The missing md_fix_up_eh_frame is used, as it was done in original code. Here just on case (IIRC it is the debug_frame one) uses it. It might be necessary to add it here for the "eh_frame" case too. But I don't see actual a reason to add all this #ifdef guarding you do.
Regards,
Kai