Problems with math.h

Problems with math.h

[tobias_meier]

Hi all,

compiling this program with the command:

gcc MatheTest.c

/* Program MatheTest.c*/
#include <stdio.h>
#include <stdlib.h>
#include <float.h>
#include <math.h>

main()
{
printf("Ergebnis %f \n", exp(2.3));
printf("Ergebnis %f \n", pow(2,3));
}

/* End Program */

I get:

cd /home/tmeier/C/Projekt01/
gcc MatheTest.c
/tmp/ccdP8Uys.o: In function `main':
/tmp/ccdP8Uys.o(.text+0xe): undefined reference to `exp'
/tmp/ccdP8Uys.o(.text+0x37): undefined reference to `pow'
collect2: ld returned 1 exit status

Compilation exited abnormally with code 1 at Thu Jan  6 22:27:58


 -> problems with math.h

looking up search dirs with command:

gcc -print-search-dirs

I get:

install: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/
programs: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/:/usr/lib/gcc-
lib/i486-linux/:/usr/lib/gcc/i486-linux/egcs-2.91.60/:/usr/lib/gcc/i486-
linux/:/usr/i486-linux/bin/i486-linux/egcs-2.91.60/:/usr/i486-linux/bin/
libraries: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/:/usr/lib/gcc/i486-
linux/egcs-2.91.60/:/usr/i486-linux/lib/i486-linux/egcs-
2.91.60/:/usr/i486-linux/lib/:/usr/lib/i486-linux/egcs-
2.91.60/:/usr/lib/:/lib/i486-linux/egcs-2.91.60/:/lib/:/usr/lib/i486-
linux/egcs-2.91.60/:/usr/lib/

searching math.h I get:
/usr/include/math.h

Ok, using option -B for gcc:

gcc -B /usr/include/math.h MatheTest.c

I get:

cd /home/tmeier/C/Projekt01/
gcc -B /usr/include/math.h MatheTest.c
/tmp/ccOFzmvH.o: In function `main':
/tmp/ccOFzmvH.o(.text+0xe): undefined reference to `exp'
/tmp/ccOFzmvH.o(.text+0x37): undefined reference to `pow'
collect2: ld returned 1 exit status
gcc: file path prefix `/usr/include/math.h' never used

Compilation exited abnormally with code 1 at Thu Jan  6 22:41:52

Compiling with g++ works:

But g++ has the same search path as gcc has !

g++ serch dirs (g++ -print-search-dirs)
install: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/
programs: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/:/usr/lib/gcc-
lib/i486-linux/:/usr/lib/gcc/i486-linux/egcs-2.91.60/:/usr/lib/gcc/i486-
linux/:/usr/i486-linux/bin/i486-linux/egcs-2.91.60/:/usr/i486-linux/bin/
libraries: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/:/usr/lib/gcc/i486-
linux/egcs-2.91.60/:/usr/i486-linux/lib/i486-linux/egcs-
2.91.60/:/usr/i486-linux/lib/:/usr/lib/i486-linux/egcs-
2.91.60/:/usr/lib/:/lib/i486-linux/egcs-2.91.60/:/lib/:/usr/lib/i486-
linux/egcs-2.91.60/:/usr/lib/


Who knows what to do ?


Sent via Deja.com http://www.deja.com/
Before you buy.

Re: Problems with math.h

[Alexandre Oliva]

On Jan  7, 2000, tobias_meier@my-deja.com wrote:

> gcc MatheTest.c
> /tmp/ccdP8Uys.o: In function `main':
> /tmp/ccdP8Uys.o(.text+0xe): undefined reference to `exp'
> /tmp/ccdP8Uys.o(.text+0x37): undefined reference to `pow'
> collect2: ld returned 1 exit status

math.h is a *header*-file, it just supplies* declarations* of the math
functions.  The *definitions* have already been compiled, and live in
the math *library*.  You can link your program with the math library
by adding `-lm' to the compile+link command.

-- 
Alexandre Oliva http://www.ic.unicamp.br/~oliva IC-Unicamp, Bra[sz]il
oliva@{lsd.ic.unicamp.br,guarana.{org,com}} aoliva@{acm,computer}.org
oliva@{gnu.org,kaffe.org,{egcs,sourceware}.cygnus.com,samba.org}
** I may forward mail about projects to mailing lists; please use them

Re: Problems with math.h

[Eric Meijer]

tobias_meier@my-deja.com wrote:
: Hi all,
: 
: compiling this program with the command:
: 
: gcc MatheTest.c

[...]

: #include <math.h>
: 
: main()
: {
: printf("Ergebnis %f \n", exp(2.3));
: printf("Ergebnis %f \n", pow(2,3));
: }

[... error:]

: /tmp/ccdP8Uys.o(.text+0xe): undefined reference to `exp'
: /tmp/ccdP8Uys.o(.text+0x37): undefined reference to `pow'

... research:

: gcc -print-search-dirs

[...]

: searching math.h I get:
: /usr/include/math.h
: 
: Ok, using option -B for gcc:
: 
: gcc -B /usr/include/math.h MatheTest.c

[...]

: Compiling with g++ works:

[ yes... ]

: But g++ has the same search path as gcc has !

[ yep ]

: Who knows what to do ?

You stumbled on a typical newbie problem.  I must say your research and
analysis of the problem are indeed impressive compared to the average
(really, no irony here).  What you need to do is read the FAQ:

http://www.faqs.org/faqs/C-faq/faq/

Most notably item 14.3, but why not read all of it?  The reason that g++
does work is in a _library_ it links by default that gcc doesn't.
Header files contain only declarations, not the functions themselves.

HTH,
Eric

-- 
 E.L. Meijer (tgakem@pebbles.chem.tue.nl)
 Eindhoven Univ. of Technology
 Lab. for Catalysis and Inorg. Chem. (SKA)

Re: Problems with math.h

[Zoran Cutura]

tobias_meier@my-deja.com wrote:
> 
> Hi all,
> 
> compiling this program with the command:
> 
> gcc MatheTest.c
> 
> /* Program MatheTest.c*/
> #include <stdio.h>
> #include <stdlib.h>
> #include <float.h>
> #include <math.h>
> 
> main()
> {
> printf("Ergebnis %f \n", exp(2.3));
> printf("Ergebnis %f \n", pow(2,3));
> }
> 
> /* End Program */
> 
> I get:
> 
> cd /home/tmeier/C/Projekt01/
> gcc MatheTest.c
> /tmp/ccdP8Uys.o: In function `main':
> /tmp/ccdP8Uys.o(.text+0xe): undefined reference to `exp'
> /tmp/ccdP8Uys.o(.text+0x37): undefined reference to `pow'
> collect2: ld returned 1 exit status
> 
> Compilation exited abnormally with code 1 at Thu Jan  6 22:27:58
> 
>  -> problems with math.h
> 
> looking up search dirs with command:
> 
> gcc -print-search-dirs
> 
> I get:
> 
> install: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/
> programs: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/:/usr/lib/gcc-
> lib/i486-linux/:/usr/lib/gcc/i486-linux/egcs-2.91.60/:/usr/lib/gcc/i486-
> linux/:/usr/i486-linux/bin/i486-linux/egcs-2.91.60/:/usr/i486-linux/bin/
> libraries: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/:/usr/lib/gcc/i486-
> linux/egcs-2.91.60/:/usr/i486-linux/lib/i486-linux/egcs-
> 2.91.60/:/usr/i486-linux/lib/:/usr/lib/i486-linux/egcs-
> 2.91.60/:/usr/lib/:/lib/i486-linux/egcs-2.91.60/:/lib/:/usr/lib/i486-
> linux/egcs-2.91.60/:/usr/lib/
> 
> searching math.h I get:
> /usr/include/math.h
> 
> Ok, using option -B for gcc:
> 
> gcc -B /usr/include/math.h MatheTest.c
> 
> I get:
> 
> cd /home/tmeier/C/Projekt01/
> gcc -B /usr/include/math.h MatheTest.c
> /tmp/ccOFzmvH.o: In function `main':
> /tmp/ccOFzmvH.o(.text+0xe): undefined reference to `exp'
> /tmp/ccOFzmvH.o(.text+0x37): undefined reference to `pow'
> collect2: ld returned 1 exit status
> gcc: file path prefix `/usr/include/math.h' never used
> 
> Compilation exited abnormally with code 1 at Thu Jan  6 22:41:52
> 
> Compiling with g++ works:
> 
> But g++ has the same search path as gcc has !
> 
> g++ serch dirs (g++ -print-search-dirs)
> install: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/
> programs: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/:/usr/lib/gcc-
> lib/i486-linux/:/usr/lib/gcc/i486-linux/egcs-2.91.60/:/usr/lib/gcc/i486-
> linux/:/usr/i486-linux/bin/i486-linux/egcs-2.91.60/:/usr/i486-linux/bin/
> libraries: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/:/usr/lib/gcc/i486-
> linux/egcs-2.91.60/:/usr/i486-linux/lib/i486-linux/egcs-
> 2.91.60/:/usr/i486-linux/lib/:/usr/lib/i486-linux/egcs-
> 2.91.60/:/usr/lib/:/lib/i486-linux/egcs-2.91.60/:/lib/:/usr/lib/i486-
> linux/egcs-2.91.60/:/usr/lib/
> 
> Who knows what to do ?
> 
> Sent via Deja.com http://www.deja.com/
> Before you buy.

-lm 

will link libm.a to yout executable!
Bye
	Z

Problems with math.h

[tobias_meier]

Hi all,

compiling this program with the command:

gcc MatheTest.c

/* Program MatheTest.c*/
#include <stdio.h>
#include <stdlib.h>
#include <float.h>
#include <math.h>

main()
{
printf("Ergebnis %f \n", exp(2.3));
printf("Ergebnis %f \n", pow(2,3));
}

/* End Program */

I get:

cd /home/tmeier/C/Projekt01/
gcc MatheTest.c
/tmp/ccdP8Uys.o: In function `main':
/tmp/ccdP8Uys.o(.text+0xe): undefined reference to `exp'
/tmp/ccdP8Uys.o(.text+0x37): undefined reference to `pow'
collect2: ld returned 1 exit status

Compilation exited abnormally with code 1 at Thu Jan  6 22:27:58


 -> problems with math.h

looking up search dirs with command:

gcc -print-search-dirs

I get:

install: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/
programs: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/:/usr/lib/gcc-
lib/i486-linux/:/usr/lib/gcc/i486-linux/egcs-2.91.60/:/usr/lib/gcc/i486-
linux/:/usr/i486-linux/bin/i486-linux/egcs-2.91.60/:/usr/i486-linux/bin/
libraries: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/:/usr/lib/gcc/i486-
linux/egcs-2.91.60/:/usr/i486-linux/lib/i486-linux/egcs-
2.91.60/:/usr/i486-linux/lib/:/usr/lib/i486-linux/egcs-
2.91.60/:/usr/lib/:/lib/i486-linux/egcs-2.91.60/:/lib/:/usr/lib/i486-
linux/egcs-2.91.60/:/usr/lib/

searching math.h I get:
/usr/include/math.h

Ok, using option -B for gcc:

gcc -B /usr/include/math.h MatheTest.c

I get:

cd /home/tmeier/C/Projekt01/
gcc -B /usr/include/math.h MatheTest.c
/tmp/ccOFzmvH.o: In function `main':
/tmp/ccOFzmvH.o(.text+0xe): undefined reference to `exp'
/tmp/ccOFzmvH.o(.text+0x37): undefined reference to `pow'
collect2: ld returned 1 exit status
gcc: file path prefix `/usr/include/math.h' never used

Compilation exited abnormally with code 1 at Thu Jan  6 22:41:52

Compiling with g++ works:

But g++ has the same search path as gcc has !

g++ serch dirs (g++ -print-search-dirs)
install: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/
programs: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/:/usr/lib/gcc-
lib/i486-linux/:/usr/lib/gcc/i486-linux/egcs-2.91.60/:/usr/lib/gcc/i486-
linux/:/usr/i486-linux/bin/i486-linux/egcs-2.91.60/:/usr/i486-linux/bin/
libraries: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/:/usr/lib/gcc/i486-
linux/egcs-2.91.60/:/usr/i486-linux/lib/i486-linux/egcs-
2.91.60/:/usr/i486-linux/lib/:/usr/lib/i486-linux/egcs-
2.91.60/:/usr/lib/:/lib/i486-linux/egcs-2.91.60/:/lib/:/usr/lib/i486-
linux/egcs-2.91.60/:/usr/lib/


Who knows what to do ?


Sent via Deja.com http://www.deja.com/
Before you buy.

Re: Problems with math.h

[Eric Meijer]

tobias_meier@my-deja.com wrote:
: Hi all,
: 
: compiling this program with the command:
: 
: gcc MatheTest.c

[...]

: #include <math.h>
: 
: main()
: {
: printf("Ergebnis %f \n", exp(2.3));
: printf("Ergebnis %f \n", pow(2,3));
: }

[... error:]

: /tmp/ccdP8Uys.o(.text+0xe): undefined reference to `exp'
: /tmp/ccdP8Uys.o(.text+0x37): undefined reference to `pow'

... research:

: gcc -print-search-dirs

[...]

: searching math.h I get:
: /usr/include/math.h
: 
: Ok, using option -B for gcc:
: 
: gcc -B /usr/include/math.h MatheTest.c

[...]

: Compiling with g++ works:

[ yes... ]

: But g++ has the same search path as gcc has !

[ yep ]

: Who knows what to do ?

You stumbled on a typical newbie problem.  I must say your research and
analysis of the problem are indeed impressive compared to the average
(really, no irony here).  What you need to do is read the FAQ:

http://www.faqs.org/faqs/C-faq/faq/

Most notably item 14.3, but why not read all of it?  The reason that g++
does work is in a _library_ it links by default that gcc doesn't.
Header files contain only declarations, not the functions themselves.

HTH,
Eric

-- 
 E.L. Meijer (tgakem@pebbles.chem.tue.nl)
 Eindhoven Univ. of Technology
 Lab. for Catalysis and Inorg. Chem. (SKA)

Re: Problems with math.h

[Zoran Cutura]

tobias_meier@my-deja.com wrote:
> 
> Hi all,
> 
> compiling this program with the command:
> 
> gcc MatheTest.c
> 
> /* Program MatheTest.c*/
> #include <stdio.h>
> #include <stdlib.h>
> #include <float.h>
> #include <math.h>
> 
> main()
> {
> printf("Ergebnis %f \n", exp(2.3));
> printf("Ergebnis %f \n", pow(2,3));
> }
> 
> /* End Program */
> 
> I get:
> 
> cd /home/tmeier/C/Projekt01/
> gcc MatheTest.c
> /tmp/ccdP8Uys.o: In function `main':
> /tmp/ccdP8Uys.o(.text+0xe): undefined reference to `exp'
> /tmp/ccdP8Uys.o(.text+0x37): undefined reference to `pow'
> collect2: ld returned 1 exit status
> 
> Compilation exited abnormally with code 1 at Thu Jan  6 22:27:58
> 
>  -> problems with math.h
> 
> looking up search dirs with command:
> 
> gcc -print-search-dirs
> 
> I get:
> 
> install: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/
> programs: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/:/usr/lib/gcc-
> lib/i486-linux/:/usr/lib/gcc/i486-linux/egcs-2.91.60/:/usr/lib/gcc/i486-
> linux/:/usr/i486-linux/bin/i486-linux/egcs-2.91.60/:/usr/i486-linux/bin/
> libraries: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/:/usr/lib/gcc/i486-
> linux/egcs-2.91.60/:/usr/i486-linux/lib/i486-linux/egcs-
> 2.91.60/:/usr/i486-linux/lib/:/usr/lib/i486-linux/egcs-
> 2.91.60/:/usr/lib/:/lib/i486-linux/egcs-2.91.60/:/lib/:/usr/lib/i486-
> linux/egcs-2.91.60/:/usr/lib/
> 
> searching math.h I get:
> /usr/include/math.h
> 
> Ok, using option -B for gcc:
> 
> gcc -B /usr/include/math.h MatheTest.c
> 
> I get:
> 
> cd /home/tmeier/C/Projekt01/
> gcc -B /usr/include/math.h MatheTest.c
> /tmp/ccOFzmvH.o: In function `main':
> /tmp/ccOFzmvH.o(.text+0xe): undefined reference to `exp'
> /tmp/ccOFzmvH.o(.text+0x37): undefined reference to `pow'
> collect2: ld returned 1 exit status
> gcc: file path prefix `/usr/include/math.h' never used
> 
> Compilation exited abnormally with code 1 at Thu Jan  6 22:41:52
> 
> Compiling with g++ works:
> 
> But g++ has the same search path as gcc has !
> 
> g++ serch dirs (g++ -print-search-dirs)
> install: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/
> programs: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/:/usr/lib/gcc-
> lib/i486-linux/:/usr/lib/gcc/i486-linux/egcs-2.91.60/:/usr/lib/gcc/i486-
> linux/:/usr/i486-linux/bin/i486-linux/egcs-2.91.60/:/usr/i486-linux/bin/
> libraries: /usr/lib/gcc-lib/i486-linux/egcs-2.91.60/:/usr/lib/gcc/i486-
> linux/egcs-2.91.60/:/usr/i486-linux/lib/i486-linux/egcs-
> 2.91.60/:/usr/i486-linux/lib/:/usr/lib/i486-linux/egcs-
> 2.91.60/:/usr/lib/:/lib/i486-linux/egcs-2.91.60/:/lib/:/usr/lib/i486-
> linux/egcs-2.91.60/:/usr/lib/
> 
> Who knows what to do ?
> 
> Sent via Deja.com http://www.deja.com/
> Before you buy.

-lm 

will link libm.a to yout executable!
Bye
	Z

Re: Problems with math.h

[Alexandre Oliva]

On Jan  7, 2000, tobias_meier@my-deja.com wrote:

> gcc MatheTest.c
> /tmp/ccdP8Uys.o: In function `main':
> /tmp/ccdP8Uys.o(.text+0xe): undefined reference to `exp'
> /tmp/ccdP8Uys.o(.text+0x37): undefined reference to `pow'
> collect2: ld returned 1 exit status

math.h is a *header*-file, it just supplies* declarations* of the math
functions.  The *definitions* have already been compiled, and live in
the math *library*.  You can link your program with the math library
by adding `-lm' to the compile+link command.

-- 
Alexandre Oliva http://www.ic.unicamp.br/~oliva IC-Unicamp, Bra[sz]il
oliva@{lsd.ic.unicamp.br,guarana.{org,com}} aoliva@{acm,computer}.org
oliva@{gnu.org,kaffe.org,{egcs,sourceware}.cygnus.com,samba.org}
** I may forward mail about projects to mailing lists; please use them