Re: About -lm switch used for linking math.h

From	Ian Collins <ian-news@hotmail.com>
Newsgroups	comp.lang.c
Subject	Re: About -lm switch used for linking math.h
Date	2012-01-28 20:38 +1300
Message-ID	<9ohmv3F8j0U11@mid.individual.net> (permalink)
References	(2 earlier) <jfuvv6$lra$1@reader1.panix.com> <8086eb21-ff6e-4f71-871d-578cfdd3d209@k6g2000vbz.googlegroups.com> <9ogivvF8j0U5@mid.individual.net> <jfv56m$u0m$1@dont-email.me> <nt07i7lj333uqi4e90merqgpovcl93mgsm@4ax.com>

Show all headers | View raw

On 01/28/12 06:24 PM, Robert Wessel wrote:
> On Fri, 27 Jan 2012 21:32:15 -0000, "BartC"<bc@freeuk.com>  wrote:
>
>>
>>
>> "Ian Collins"<ian-news@hotmail.com>  wrote in message
>> news:9ogivvF8j0U5@mid.individual.net...
>>> On 01/28/12 09:26 AM, Malcolm McLean wrote:
>>>> On Jan 27, 8:03 pm, j...@panix.com (Joe keane) wrote:
>>>>>
>>>>> One day, C was just a language.  People wrote some utility functions.
>>>>>
>>>> Most languages had input and output statements. Many had special built
>>>> in functions.
>>>>
>>>> C was a bit different. Everything in the language proper mapped to two
>>>> or three assembly instructions. Everything else was a function. There
>>>> was no difference between user-defined functions and built in ines,
>>>> and virtually every function could be implemented in C.
>>>>
>>>> The library grew up with the language, however.
>>>
>>> The library also grew to be pretty big in comparison with the "standard"
>>> library.  On early machines there wasn't any hardware floating point
>>> support and RAM was a precious resource, so a separate library made sense.
>>
>> Perhaps I no longer understand what the purpose of a linker is, but I
>> thought that they extracted only the functions that were needed from a
>> library (and any further functions that *they* depend on). It was not
>> necessary to load the entire library. So linking in a maths module should
>> not make the program any bigger, if no maths functions are actually used.
>>
>> (Certainly, when I one time decided to dispense with the services of a
>> linker, and wrote my own loader, that loader was very fast just because it
>> *did* just load libraries in their entirety.)
>
>
> They usually do, although it depends on the library writers having
> done a competent job of segmenting the objects that go into the
> library.
>
> Probably a more significant issue is that you can't actually do that
> for C, because functions like printf() cannot easily be classified as
> using, or not using, floating point, since the usage depends on the
> format strings being passed in.  So you'd usually get much of the FP
> library since printf() *might* need it (and remember that on many
> small machines, including many of the earlier ones, the FP library
> included the emulation code for the basic FP operations).

Are you confusing floating point arithmetic (and it's emulation) with 
the floating point mathematical functions in libm?  Functions like 
printf() would certainly use the former, but not the latter.

-- 
Ian Collins

Thread

About -lm switch used for linking math.h Avinash Sonawane <avinash.sonawane1990@gmail.com> - 2012-01-26 13:59 -0800
  Re: About -lm switch used for linking math.h Keith Thompson <kst-u@mib.org> - 2012-01-26 14:15 -0800
  Re: About -lm switch used for linking math.h James Kuyper <jameskuyper@verizon.net> - 2012-01-26 17:17 -0500
    Re: About -lm switch used for linking math.h Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-01-26 20:54 -0500
    Re: About -lm switch used for linking math.h Kaz Kylheku <kaz@kylheku.com> - 2012-01-27 02:12 +0000
  Re: About -lm switch used for linking math.h jacob navia <jacob@spamsink.net> - 2012-01-26 23:29 +0100
  Re: About -lm switch used for linking math.h Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2012-01-26 23:09 -0700
    Re: About -lm switch used for linking math.h jacob navia <jacob@spamsink.net> - 2012-01-27 08:37 +0100
    Re: About -lm switch used for linking math.h gazelle@shell.xmission.com (Kenny McCormack) - 2012-01-27 09:48 +0000
      OT:Re: About -lm switch used for linking math.h Kleuske <kleuske@nowhere.net> - 2012-01-27 10:15 +0000
        Re: OT:Re: About -lm switch used for linking math.h gazelle@shell.xmission.com (Kenny McCormack) - 2012-01-27 14:43 +0000
          Re: OT:Re: About -lm switch used for linking math.h tom st denis <tom@iahu.ca> - 2012-01-27 07:49 -0800
            Re: OT:Re: About -lm switch used for linking math.h gazelle@shell.xmission.com (Kenny McCormack) - 2012-01-27 15:55 +0000
              Re: OT:Re: About -lm switch used for linking math.h tom st denis <tom@iahu.ca> - 2012-01-27 10:14 -0800
            Re: OT:Re: About -lm switch used for linking math.h Keith Thompson <kst-u@mib.org> - 2012-01-27 11:23 -0800
          Re: OT:Re: About -lm switch used for linking math.h Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2012-01-27 09:42 -0700
            Re: OT:Re: About -lm switch used for linking math.h 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-28 14:08 -0800
        Re: OT:Re: About -lm switch used for linking math.h Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-02-14 13:14 +0200
      Re: About -lm switch used for linking math.h Rui Maciel <rui.maciel@gmail.com> - 2012-01-27 16:56 +0000
        Re: About -lm switch used for linking math.h gazelle@shell.xmission.com (Kenny McCormack) - 2012-01-27 17:34 +0000
          Re: About -lm switch used for linking math.h Rui Maciel <rui.maciel@gmail.com> - 2012-01-27 17:50 +0000
          Re: About -lm switch used for linking math.h Kaz Kylheku <kaz@kylheku.com> - 2012-01-27 17:58 +0000
            Re: About -lm switch used for linking math.h tom st denis <tom@iahu.ca> - 2012-01-27 10:15 -0800
            Re: About -lm switch used for linking math.h gazelle@shell.xmission.com (Kenny McCormack) - 2012-01-27 19:25 +0000
              Re: About -lm switch used for linking math.h Kleuske <kleuske@nowhere.net> - 2012-01-28 18:09 +0000
            Re: About -lm switch used for linking math.h jt@toerring.de (Jens Thoms Toerring) - 2012-01-27 21:32 +0000
    Re: About -lm switch used for linking math.h "Wolfgang.Draxinger" <Wolfgang.Draxinger@physik.uni-muenchen.de> - 2012-01-27 12:40 +0100
      Re: About -lm switch used for linking math.h "BartC" <bc@freeuk.com> - 2012-01-27 12:48 +0000
        Re: About -lm switch used for linking math.h Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-27 14:28 +0000
      Re: About -lm switch used for linking math.h Kaz Kylheku <kaz@kylheku.com> - 2012-01-27 17:14 +0000
        Re: About -lm switch used for linking math.h gazelle@shell.xmission.com (Kenny McCormack) - 2012-01-27 17:34 +0000
      Re: About -lm switch used for linking math.h Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2012-01-27 10:43 -0700
    Re: About -lm switch used for linking math.h Stephen Sprunk <stephen@sprunk.org> - 2012-01-27 12:25 -0600
      Re: About -lm switch used for linking math.h "BartC" <bc@freeuk.com> - 2012-01-27 18:41 +0000
        Re: About -lm switch used for linking math.h James Kuyper <jameskuyper@verizon.net> - 2012-01-27 13:45 -0500
          Re: About -lm switch used for linking math.h Keith Thompson <kst-u@mib.org> - 2012-01-27 11:29 -0800
        Re: About -lm switch used for linking math.h Jens Gustedt <jens.gustedt@loria.fr> - 2012-01-27 22:35 +0100
        Re: About -lm switch used for linking math.h Stephen Sprunk <stephen@sprunk.org> - 2012-01-27 17:19 -0600
          Re: About -lm switch used for linking math.h James Kuyper <jameskuyper@verizon.net> - 2012-01-27 19:22 -0500
            Re: About -lm switch used for linking math.h Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-31 23:32 -0800
          Re: About -lm switch used for linking math.h Keith Thompson <kst-u@mib.org> - 2012-01-27 16:26 -0800
            Re: About -lm switch used for linking math.h Ian Collins <ian-news@hotmail.com> - 2012-01-28 13:30 +1300
              Re: About -lm switch used for linking math.h Keith Thompson <kst-u@mib.org> - 2012-01-27 17:04 -0800
                Re: About -lm switch used for linking math.h Ian Collins <ian-news@hotmail.com> - 2012-01-28 14:10 +1300
                Re: About -lm switch used for linking math.h Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-01-27 21:06 -0500
                Re: About -lm switch used for linking math.h Keith Thompson <kst-u@mib.org> - 2012-01-27 20:09 -0800
                Re: About -lm switch used for linking math.h Keith Thompson <kst-u@mib.org> - 2012-01-27 20:15 -0800
              Re: About -lm switch used for linking math.h Stephen Sprunk <stephen@sprunk.org> - 2012-01-27 23:03 -0600
                Re: About -lm switch used for linking math.h Ian Collins <ian-news@hotmail.com> - 2012-01-28 19:10 +1300
                Re: About -lm switch used for linking math.h Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-01-28 04:28 -0800
                Re: About -lm switch used for linking math.h Stephen Sprunk <stephen@sprunk.org> - 2012-01-28 15:25 -0600
                Re: About -lm switch used for linking math.h Ian Collins <ian-news@hotmail.com> - 2012-01-29 11:39 +1300
                Re: About -lm switch used for linking math.h Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-01-29 09:53 -0800
                Re: About -lm switch used for linking math.h Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-02-03 10:39 +0000
                Re: About -lm switch used for linking math.h Joshua Maurice <joshuamaurice@gmail.com> - 2012-02-01 16:42 -0800
                Re: About -lm switch used for linking math.h jgk@panix.com (Joe keane) - 2012-02-02 01:29 +0000
                Re: About -lm switch used for linking math.h Keith Thompson <kst-u@mib.org> - 2012-01-28 15:22 -0800
                Re: About -lm switch used for linking math.h Stephen Sprunk <stephen@sprunk.org> - 2012-01-29 16:52 -0600
                Re: About -lm switch used for linking math.h Keith Thompson <kst-u@mib.org> - 2012-01-30 02:04 -0800
                Re: About -lm switch used for linking math.h Ike Naar <ike@iceland.freeshell.org> - 2012-01-30 10:22 +0000
                Re: About -lm switch used for linking math.h Keith Thompson <kst-u@mib.org> - 2012-01-30 02:36 -0800
                Re: About -lm switch used for linking math.h Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-02-14 13:33 +0200
                Re: About -lm switch used for linking math.h Ike Naar <ike@iceland.freeshell.org> - 2012-02-14 23:48 +0000
                Re: About -lm switch used for linking math.h Keith Thompson <kst-u@mib.org> - 2012-02-14 16:35 -0800
                Re: About -lm switch used for linking math.h Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-02-22 02:44 +0200
                Re: About -lm switch used for linking math.h Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-01-30 04:30 -0800
                Re: About -lm switch used for linking math.h Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-30 14:36 +0000
                Re: About -lm switch used for linking math.h Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-31 23:50 -0800
                Re: About -lm switch used for linking math.h Keith Thompson <kst-u@mib.org> - 2012-01-28 15:29 -0800
                Re: About -lm switch used for linking math.h Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-01-29 09:11 -0800
                Re: About -lm switch used for linking math.h "BartC" <bc@freeuk.com> - 2012-01-29 17:49 +0000
                Re: About -lm switch used for linking math.h Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-01-29 10:07 -0800
                Re: About -lm switch used for linking math.h Keith Thompson <kst-u@mib.org> - 2012-01-29 14:24 -0800
                Re: About -lm switch used for linking math.h Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-01-29 09:43 -0800
            Re: About -lm switch used for linking math.h Keith Thompson <kst-u@mib.org> - 2012-01-27 16:54 -0800
              Re: About -lm switch used for linking math.h Kaz Kylheku <kaz@kylheku.com> - 2012-01-28 01:09 +0000
                Re: About -lm switch used for linking math.h Ian Collins <ian-news@hotmail.com> - 2012-01-28 14:20 +1300
                Re: About -lm switch used for linking math.h Azazel <azazel@remove.azazel.net> - 2012-01-30 17:40 -0600
                Re: About -lm switch used for linking math.h Kaz Kylheku <kaz@kylheku.com> - 2012-01-31 00:05 +0000
    Re: About -lm switch used for linking math.h jgk@panix.com (Joe keane) - 2012-01-27 20:03 +0000
      Re: About -lm switch used for linking math.h Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-01-27 12:26 -0800
        Re: About -lm switch used for linking math.h Ian Collins <ian-news@hotmail.com> - 2012-01-28 10:24 +1300
          Re: About -lm switch used for linking math.h "BartC" <bc@freeuk.com> - 2012-01-27 21:32 +0000
            Re: About -lm switch used for linking math.h James Kuyper <jameskuyper@verizon.net> - 2012-01-27 16:39 -0500
            Re: About -lm switch used for linking math.h Robert Wessel <robertwessel2@yahoo.com> - 2012-01-27 23:24 -0600
              Re: About -lm switch used for linking math.h Ian Collins <ian-news@hotmail.com> - 2012-01-28 20:38 +1300
                Re: About -lm switch used for linking math.h Robert Wessel <robertwessel2@yahoo.com> - 2012-01-28 02:17 -0600
              Re: About -lm switch used for linking math.h Richard Damon <news.x.richarddamon@xoxy.net> - 2012-01-28 14:07 -0500
                Re: About -lm switch used for linking math.h Robert Wessel <robertwessel2@yahoo.com> - 2012-01-28 15:07 -0600
        Re: About -lm switch used for linking math.h jgk@panix.com (Joe keane) - 2012-01-28 21:09 +0000
      Re: About -lm switch used for linking math.h Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2012-01-27 21:39 -0700
        Re: About -lm switch used for linking math.h Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-28 11:21 +0000
          Re: About -lm switch used for linking math.h Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2012-01-28 17:51 -0700
            Re: About -lm switch used for linking math.h Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-29 02:03 +0000
      Re: About -lm switch used for linking math.h Kaz Kylheku <kaz@kylheku.com> - 2012-01-28 18:58 +0000
        Re: About -lm switch used for linking math.h jacob navia <jacob@spamsink.net> - 2012-01-28 20:48 +0100
          Re: About -lm switch used for linking math.h Robert Wessel <robertwessel2@yahoo.com> - 2012-01-28 22:54 -0600
      Re: About -lm switch used for linking math.h jgk@panix.com (Joe keane) - 2012-01-29 21:42 +0000
        Re: About -lm switch used for linking math.h Robert Wessel <robertwessel2@yahoo.com> - 2012-01-30 00:14 -0600
  Re: About -lm switch used for linking math.h Stephen Sprunk <stephen@sprunk.org> - 2012-01-27 11:12 -0600

csiph-web