what's up with the math library?

[hippocampe]

I'm doing a very simple program including calls to cos and sqrt functions.

I get this when compiling:

/home/hippocampe/tmp/ccSzTSx5.o(.text+0x31): In function `main':

: undefined reference to `cos'

/home/hippocampe/tmp/ccSzTSx5.o(.text+0x4d): In function `main':

: undefined reference to `sqrt'

collect2: ld returned 1 exit status

 

Before you ask, I did include math.h :)

The program compiles but does not build in Anjuta.

It builds when I comment the lines containing these functions.

My system is Mandrake 9.1. I don't know if my system is missing any packages?

Thanks

 

PS: Somehow it works when I use g++ instead of gcc at the command line. Anjuta uses gcc so I get error messages when I build from there.

Anyone has an idea what is causing this? The file extension is .c

[johnnyv]

when using gcc did you include the link flag for the math library ?

 

eg) gcc src.c -lm

 

-lm links to the math library

[baudolino]

add the option -lm to the gcc command.

look also at 14.3 in the C-faq linked below

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

 

baudo

[hippocampe]

Thanks guys, that definitely solved it.

I'm actually surprised I didn't come across this before....

So you actually need to explicitely link to the math library?

I'm surprised that it's not included by default when you include the corresponding header.

Why did it work with g++ without the -lm option?