Re: [RFC] Move static archive dependencies into ld

[Howard Chu <hyc@symas.com>]

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What needs to happen to move this RFC forward? There seems to be at least some support for the idea (attached)

Howard Chu wrote:
> Michael Matz via Binutils wrote:
>> Hello,
>>
>> this is an RFC for now.  When met with some acceptance I'll cobble up a 
>> similar thing for gold as well and then make the libdep.so plugin only 
>> emit a warning message that its functionality is obsoleted and moved 
>> into ld itself.  As Cary put it back in 2020 when the plugin was added:
>>
>> ( https://sourceware.org/pipermail/binutils/2020-December/114536.html )
>>
>> "Did I miss any discussion about whether this feature should/could be
>> implemented directly in the linkers, rather than via a plugin? I
>> wouldn't be opposed to it."
> 
> I'm all for it. I went the plugin route initially because it seemed the
> easiest way to get the feature written and accepted but I agree with you,
> it'd be much more useful if it was implicitly supported by default.
>>
>> I pretty much think that yes, the functionality absolutely needs to be in 
>> the linker itself, not in a plugin, at least if we want to see some use of 
>> it in the real world.  Amusingly I was triggered to look into this by 
>> libbfd itself:  Recently it got a dependency to libsframe and when 
>> shipping only static archives to build against (which we as distro 
>> consciously do) that leads to build errors in various 3rdparty packages 
>> wanting to link against libbfd (no matter how bad an idea that is).  Now, 
>> adding a '-plugin $magicdir/libdep.so' to the build flags of each such 
>> package is no better than just adding '-lsframe' in each case, so the 
>> plugin really doesn't help anything.  Had the functionality already been 
>> in the linker itself we could have just added 
>> "--record-libdeps='-lsframe'" when building libbfd.a and be done with it.
>>
>> So, let's try to prepare for the future and at least now make ld interpret 
>> such dependencies on its own.
>>
>> So, what do people think?
>>
>>
>> Ciao,
>> Michael.
>>
>> ---------------------------------------
>>
>> needing a plugin to interpret static archive dependencies (as added
>> by 'ar --record-libdeps') effectively means they are unused.
>> Which is too bad, because they are actually useful.  So implement
>> them in ld itself.
> 
> 
> 


-- 
  -- Howard Chu
  CTO, Symas Corp.           http://www.symas.com
  Director, Highland Sun     http://highlandsun.com/hyc/
  Chief Architect, OpenLDAP  http://www.openldap.org/project/

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From: Howard Chu <hyc@symas.com>
To: "Clément Chigot" <chigot@adacore.com>, binutils@sourceware.org
Subject: Re: [PATCH] ld: build libdep plugin only when shared library support is enabled
Date: Thu, 13 Apr 2023 09:54:02 +0100
Message-ID: <5216d67e-ab2b-8142-edd8-4cab38ee2dc6@symas.com>

Clément Chigot via Binutils wrote:
> Otherwise, libtool will create a static plugin which cannot be loaded.
> Even worse on Windows, it will create a .a file, resulting in a similar
> bug than PR 27113: some tools will try to open it and Windows will raise
> a popup error.

At this point I think it'd be better to integrate the libdep functionality directly into ld, as suggested before:

https://sourceware.org/pipermail/binutils/2023-February/126155.html

-- 
  -- Howard Chu
  CTO, Symas Corp.           http://www.symas.com
  Director, Highland Sun     http://highlandsun.com/hyc/
  Chief Architect, OpenLDAP  http://www.openldap.org/project/