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| From | Eric Sosman <esosman@ieee-dot-org.invalid> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: About -lm switch used for linking math.h |
| Date | 2012-01-26 20:54 -0500 |
| Organization | A noiseless patient Spider |
| Message-ID | <jft055$8gi$1@dont-email.me> (permalink) |
| References | <33220336.277.1327615195035.JavaMail.geo-discussion-forums@prnc5> <jfsjdl$1s8$1@dont-email.me> |
On 1/26/2012 5:17 PM, James Kuyper wrote:
> On 01/26/2012 04:59 PM, Avinash Sonawane wrote:
>> 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?
>
> #include<math.h> tells the compiler which library header to insert into
> your program when compiling. -lm tells the linker which library to
> search when linking your compiled program. A compiler could connect the
> two, but most of the ones I'm familiar with don't.
>
>> 2) If it's all about linking the library then why I don't have to do
>> the same thing with stdio.h too?
>
> By convention dating back to the early days of C, most of the C standard
> library is often stored in one library file, except for the part
> described by<math.h>, which is stored in a different one. This approach
> became conventional because, especially at that time, most programs made
> no use of the math library, and adding all of those functions to the
> linker's search would significantly slowed down linkage. This is far
> less of an issue now than it used to be, but some habits, once started,
> are hard to change.
In at least one C implementation, the math functions have in
fact been combined with the rest of the library and all are linked
automatically with no need for -lm. This implementation also provides
a completely empty "libm" library, just to accommodate Makefiles and
so on that use -lm anyhow!
--
Eric Sosman
esosman@ieee-dot-org.invalid
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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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