From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <tdevries@suse.de>
Received: from mx2.suse.de (mx2.suse.de [195.135.220.15])
 by sourceware.org (Postfix) with ESMTPS id 7EF5D38618F1
 for <dwz@sourceware.org>; Wed, 17 Mar 2021 10:46:52 +0000 (GMT)
DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 7EF5D38618F1
Authentication-Results: sourceware.org;
 dmarc=none (p=none dis=none) header.from=suse.de
Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=tdevries@suse.de
X-Virus-Scanned: by amavisd-new at test-mx.suse.de
Received: from relay2.suse.de (unknown [195.135.221.27])
 by mx2.suse.de (Postfix) with ESMTP id A256BAC23;
 Wed, 17 Mar 2021 10:46:51 +0000 (UTC)
Subject: Re: [PATCH] Add --devel-skip-producer
To: Mark Wielaard <mark@klomp.org>
Cc: dwz@sourceware.org, jakub@redhat.com
References: <20210316141919.GA24635@delia>
 <20210316212749.GC3054@wildebeest.org>
From: Tom de Vries <tdevries@suse.de>
Message-ID: <0956da43-2f83-83a8-1da2-63916d4b49f6@suse.de>
Date: Wed, 17 Mar 2021 11:46:51 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.8.0
MIME-Version: 1.0
In-Reply-To: <20210316212749.GC3054@wildebeest.org>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
X-Spam-Status: No, score=-6.2 required=5.0 tests=BAYES_00, KAM_DMARC_STATUS,
 NICE_REPLY_A, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS,
 TXREP autolearn=ham autolearn_force=no version=3.4.2
X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on
 server2.sourceware.org
X-BeenThere: dwz@sourceware.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Dwz mailing list <dwz.sourceware.org>
List-Unsubscribe: <https://sourceware.org/mailman/options/dwz>,
 <mailto:dwz-request@sourceware.org?subject=unsubscribe>
List-Archive: <https://sourceware.org/pipermail/dwz/>
List-Help: <mailto:dwz-request@sourceware.org?subject=help>
List-Subscribe: <https://sourceware.org/mailman/listinfo/dwz>,
 <mailto:dwz-request@sourceware.org?subject=subscribe>
X-List-Received-Date: Wed, 17 Mar 2021 10:46:53 -0000

On 3/16/21 10:27 PM, Mark Wielaard wrote:
> Hi Tom,
> 
> On Tue, Mar 16, 2021 at 03:19:20PM +0100, Tom de Vries wrote:
>> In PR27588 a test-case was reported where dwz did not optimize due
>> to illegal DWARF produced by nasm:
>> ...
>> $ dwz libxul.so -o libxul.so.z
>> dwz: libxul.so: loclistptr attribute, yet no .debug_loc section
>> ...
>>
>> Add an option --devel-skip-producer <producer> such that we can filter out
>> CUs coming from a particular producer, such that we have instead:
>> ...
>> $ readelf -wi libxul.so | grep DW_AT_producer \
>>     | sed 's/.*: //' | sort | uniq -c
>>     176 clang LLVM (rustc version 1.50.0)
>>       2 GNU AS 2.36.1
>>       2 GNU C11 11.0.1 20210315 (experimental) <SNIP>
>>      16 NASM 2.15.05
>>      76 yasm 1.3.0
>> $ dwz libxul.so -o libxul.so.z --devel-skip-producer NASM
>> $ readelf -wi libxul.so.z | grep DW_AT_producer \
>>     | sed 's/.*: //' | sort | uniq -c
>>     176 clang LLVM (rustc version 1.50.0)
>>       2 GNU AS 2.36.1
>>       2 GNU C11 11.0.1 20210315 (experimental) <SNIP>
>>      76 yasm 1.3.0
>> ...
>>
>> Any comments?
> 
> So this skips and then removes the whole CU (because we set die_remove
> on the cu_die)?
> 

Yes.

> It is useful as --devel option, but I would be against it as non-devel
> option.

Could you explain in more detail why you would be against this as a
non-devel option?  F.i., I'm curious, is it an abstract objection, or do
you foresee concrete problems with the approach?

Thanks,
- Tom