From: "Jan Beulich" <JBeulich@novell.com>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: <binutils@sourceware.org>
Subject: Re: discarding rules for duplicate ELF comdat groups
Date: Fri, 28 Jan 2011 15:28:00 -0000 [thread overview]
Message-ID: <4D42EEA3020000780002F31E@vpn.id2.novell.com> (raw)
In-Reply-To: <AANLkTinh=VfzA7yHPUWzpAn0eHaNRYH9R-izKZdtYoOd@mail.gmail.com>
>>> On 28.01.11 at 15:40, "H.J. Lu" <hjl.tools@gmail.com> wrote:
> On Fri, Jan 28, 2011 at 6:30 AM, Jan Beulich <JBeulich@novell.com> wrote:
>>>>> On 28.01.11 at 15:07, "H.J. Lu" <hjl.tools@gmail.com> wrote:
>>> On Fri, Jan 28, 2011 at 5:51 AM, Jan Beulich <JBeulich@novell.com> wrote:
>>>> It seems like currently the rule simply is to pick the first instance the
>>>> linker gets to see. Wouldn't it make sense to honor the group
>>>> signature's attributed (namely its binding), and prefer keeping an
>>>> instance with a global group signature over a weak or local one?
>>>> That would allow the programmer some control over which
>>>> instance to keep: My main motivation is to find a way to discard
>>>> the various weak fallback functions Linux has to cover cases where
>>>> e.g. some architectures implement certain functionality, while
>>>> others that don't can all use a generic implementation.
>>>>
>>>> I cannot see other mechanisms that would allow ld to discard
>>>> sections (not to speak of individual functions within sections).
>>>>
>>>
>>> Microsoft linker has some user controls over which comdat group
>>> instance to keep. Will its scheme work for you?
>>
>> I'm not aware of any such controls - can you point me to
>> something describing this?
>
> /* COMDAT selection codes. */
>
> #define IMAGE_COMDAT_SELECT_NODUPLICATES (1) /* Warn if duplicates. */
> #define IMAGE_COMDAT_SELECT_ANY (2) /* No warning. */
> #define IMAGE_COMDAT_SELECT_SAME_SIZE (3) /* Warn if different size.
> */
> #define IMAGE_COMDAT_SELECT_EXACT_MATCH (4) /* Warn if different. */
> #define IMAGE_COMDAT_SELECT_ASSOCIATIVE (5) /* Base on other section.
> */
Oh, those you meant. No, they don't allow controlling which
instance will be retained.
Jan
next prev parent reply other threads:[~2011-01-28 15:28 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-28 13:51 Jan Beulich
2011-01-28 14:07 ` H.J. Lu
2011-01-28 14:30 ` Jan Beulich
2011-01-28 14:40 ` H.J. Lu
2011-01-28 15:28 ` Jan Beulich [this message]
2011-01-28 15:56 ` H.J. Lu
[not found] ` <4D4305B6020000780002F372@vpn.id2.novell.com>
[not found] ` <AANLkTi=0RD6pYbPjXYJ3tk429WAtBa555GP1ksBedLO9@mail.gmail.com>
2011-01-31 8:02 ` Jan Beulich
2011-01-31 18:19 ` Ian Lance Taylor
2011-02-01 9:14 Jan Beulich
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