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Groups > comp.lang.c > #16273

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

From jacob navia <jacob@spamsink.net>
Newsgroups comp.lang.c
Subject Re: About -lm switch used for linking math.h
Date 2012-01-26 23:29 +0100
Organization lccwin
Message-ID <jfsk3m$v2n$1@speranza.aioe.org> (permalink)
References <33220336.277.1327615195035.JavaMail.geo-discussion-forums@prnc5>

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Le 26/01/12 22:59, Avinash Sonawane a écrit :
> Sir,
> I am using gcc 4.6.1.
> I have few questions regarding -lm switch. Please kindly guide me for the same.
>
> 1) Why I need to use -lm flag for math.h even if I had declared the
> #include<math.h>  in the code?

Because you do not have a Macintosh. If you would have one, you
wouldn't need that.

> 2) If it's all about linking the library then why I don't have to do
> the same thing with stdio.h too?

Because of hysterical reasons.

> 3) Or we have to add the -l'library' switch for every library excluding stdio.h?

Yes. For each library you should add the corresponding name to the link 
command.

> 4) In case if the -l'library' switch is used for some specific
> libraries only then please direct me to the complete list of such
> libraries.
>

The -l'library' switch is needed for all the libraries not included
by default. Most linkers include some libraries by default, at least
the C library (that is why you do not need to include the stdio
library).

In more advanced systems, there is no distinction between the stdio
library and the mathematical library: they are all part of the C
library and included by default. Those systems do NOT need any -lm
switch. There are other systems that provide many more libraries
included by default.

There are some linkers/IDE combinations that have a small database
of which functions are included in which library so that it isn't
needed to remember the name of the library, the IDE just consults
its database and figures out the correct switch for the linker.

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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

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