[RFC] libm replacement for Busybox

[walter harms]

Rob Landley schrieb:
> On Friday 10 October 2008 12:07:52 walter harms wrote:
>> Bernhard Reutner-Fischer schrieb:
>>> On Fri, Oct 10, 2008 at 04:21:51PM +0200, Loïc Grenié wrote:
>>>>     I've noticed that busybox uses few functions from libm.
>>> Actually, you can turn off ASH_MATH_SUPPORT_64 FEATURE_AWK_MATH and
>>> you don't need libm at all.
>>>
>>>>  I've written some replacements for those functions. Right
>>>>  now this is just the test program and I've not made the
>>>>  effort of including them in Busybox. However I'd like to
>>>>  have your opinion: would it be a good idea to include
>>>>  them ?
>>> I don't think so (but perhaps vda likes it anyway). Just:
>>> 1) turn off the abovementioned two features
>>> or, if either of that is really needed desperately, you can
>>> 2a) link busybox statically (very likely in the scenarios you mention
>>>   below)
>>> 2b) Use a trimmed libm which only contains those few functions that will
>>>   be needed by your initramfs (usually 0, see #1 above).
>>>
>>>>    They are neither very fast nor very precise (the
>>>>  trigonometric functions are awful, up to 16 bits are
>>>>  false) but libm is rather large and usually a user of
>>>>  Busybox on an initrd or embedded platform does not
>>>>  need neither speed nor excellent precision. Otherwise
>>> I think that neither of them need ASH_MATH_SUPPORT_64 FEATURE_AWK_MATH,
>>> so busybox wouldn't link against libm anyway.
>> Hi Bernhard,
>> you are right but the idea is nice and we do not have a lot of libm
>> functions.
>>
>> Perhaps we can put these functions on the bb webpage ?
> 
> Well, considering uclibc.org is the same server as busybox, they sort of 
> already are.
> 
no problem with that but it goes beyond what i intended with that.
Perhaps someone else from ulibc would like to continue that work maybe loic will.


>> We should add something like supplements/unsupported stuff to keep good
>> idea that are not incorporate for one reason or an other.
> 
> Whatever happened to "simple"?  Small, simple, not having 8 gazillion #ifdefs 
> like the gnu bloatware that takes all day to figure out what code connects to 
> what and which of the conflicting implementations for any given chunk of 
> functionality winds up being used...
> 
> I liked simple.

i do not understand. we all like the "simple" stuff else we would write
bloaty-clicky-bunty stuff that needs 3GHz just to start.

Sometimes people post ideas that do not fit exactly into busysbox (like this libm stuff).
It is a valid idea. it is a good idea. BUT I (am not the maintainer)  would not include it
because there is already a libm and it is not my "job" to optimize it.
The maintainer could add #ifdef avoid_libm but that leads to the #ifdef forest you
(and most others) would like to avoid.
Still it is a good idea, so why not store it somewhere ? space is cheap this days.
maybe someone else (e.g. the ulibc guys) will pick it up, incorporated and expand it.
IMHO the most easy solution for everyone.

re,
 wh