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Re: USE_LSB_TAG not supported on this platform
From: |
Colin Baxter |
Subject: |
Re: USE_LSB_TAG not supported on this platform |
Date: |
Wed, 10 Feb 2016 19:29:58 +0000 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.1.50 (gnu/linux) |
>> Cc: address@hidden, address@hidden, address@hidden
>> From: Paul Eggert <address@hidden>
>> Date: Tue, 9 Feb 2016 09:37:15 -0800
>>
>> On 02/09/2016 08:59 AM, Eli Zaretskii wrote:
>> > Thanks. Out of curiosity: which hosts can behave like that?
>>
>> 16-bit PDP-11s running 7th Edition Unix. malloc returned only a multiple
>> of 2 there. :-)
>
> There's only one 16-bit platform supported by Emacs: MS-DOS. And
> there the problem doesn't exist, because the library switches the CPU
> to 32-bit mode.
>
>> > Also, why are we sure that the loops will end at some point on those
>> > hosts? Shouldn't we perhaps set a limit to the loop iterations, to be
>> > sure we don't infloop there?
>>
>> We're not absolutely sure. Certainly the C standard doesn't guarantee
>> it; malloc can return a pointer that is always odd, on weird platforms
>> where alignof always returns 1. I view this as almost purely theoretical
>> though, due to the practical performance benefit of alignment to at
>> least sizeof(double). It's conceivable (though very unlikely) that Emacs
>> will infloop on some truly oddball platform that does not care about
>> performance; but if that happens it'll be OK, as the infloop would
>> almost surely happen during a build and the builder would then send us a
>> bug report and we can deal with it then. I think adding a counter would
>> complicate the code (and possibly introduce bugs, in code that's never
>> really exercised) for not enough benefit.
>
> Maybe these considerations are worth having as comments near the loop,
> so that whoever bumps into the problem will know faster and better
> what to do.
>
> Thanks.
You might like to know that the latest git-pull builds satisfactorily
for me, giving Emacs 25.1.50.1 (i686-pc-linux-gnu, GTK+ Version 3.4.2)
of 2016-02-10
Best wishes,
Colin.
- Re: USE_LSB_TAG not supported on this platform, (continued)
- Re: USE_LSB_TAG not supported on this platform, Herbert J. Skuhra, 2016/02/06
- Re: USE_LSB_TAG not supported on this platform, Wolfgang Jenkner, 2016/02/07
- Re: USE_LSB_TAG not supported on this platform, Herbert J. Skuhra, 2016/02/07
- Re: USE_LSB_TAG not supported on this platform, Herbert J. Skuhra, 2016/02/07
- Re: USE_LSB_TAG not supported on this platform, Paul Eggert, 2016/02/08
- Re: USE_LSB_TAG not supported on this platform, Eli Zaretskii, 2016/02/08
- Re: USE_LSB_TAG not supported on this platform, Paul Eggert, 2016/02/09
- Re: USE_LSB_TAG not supported on this platform, Eli Zaretskii, 2016/02/09
- Re: USE_LSB_TAG not supported on this platform, Paul Eggert, 2016/02/09
- Re: USE_LSB_TAG not supported on this platform, Eli Zaretskii, 2016/02/09
- Re: USE_LSB_TAG not supported on this platform,
Colin Baxter <=
- Re: USE_LSB_TAG not supported on this platform, Herbert J. Skuhra, 2016/02/08
- Re: USE_LSB_TAG not supported on this platform, Paul Eggert, 2016/02/08
- Re: USE_LSB_TAG not supported on this platform, Herbert J. Skuhra, 2016/02/09
- Re: USE_LSB_TAG not supported on this platform, Paul Eggert, 2016/02/09
- Re: USE_LSB_TAG not supported on this platform, Wolfgang Jenkner, 2016/02/09
- Re: USE_LSB_TAG not supported on this platform, Paul Eggert, 2016/02/09
- Re: USE_LSB_TAG not supported on this platform, Paul Eggert, 2016/02/06
- Re: USE_LSB_TAG not supported on this platform, Herbert J. Skuhra, 2016/02/07
- Re: USE_LSB_TAG not supported on this platform, Paul Eggert, 2016/02/07