Error using math.h

Discussion:

Error using math.h

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Javid Sumayya

2004-01-18 21:31:03 UTC

hi

I am having problems with using the power function in math.h
I have included the math.h file by writing #include <math.h>
and used the power function by calling pow(x,y)...where x and
y are two double variables
But for some reason it is giving me an error saying
"undefined reference to pow".

Thankx

Sherman

2004-01-20 03:07:59 UTC

Permalink

Is it just problems with "pow"? Cuz for me no matter what function I tried
using, it still gave me "undefined referene to (the function)".
And i #include <math.h> already so y is it still happening?

Sherman

Post by Javid Sumayya
hi
I am having problems with using the power function in math.h
I have included the math.h file by writing #include <math.h>
and used the power function by calling pow(x,y)...where x and
y are two double variables
But for some reason it is giving me an error saying
"undefined reference to pow".
Thankx

Robert Chang

2004-01-20 15:11:00 UTC

Permalink

Try adding -lm

Eg: gcc -o foo foo.c -lm

Alexander Smith

2004-01-20 16:55:13 UTC

Permalink

In general, if you want to use <math.h>, you need to link your program
with the math library. This is what the "-lm" command does. In a Makefile,
the -lm would be added to the line that links all of your object files
together into the executable file.

However, for lab 1, you are not allowed to modify the Makefile. This means
that for lab 1, you cannot use math.h. You don't actually need any
functions in it anyways - not even pow(). You should be able to do the lab
without it.

Alexander

Post by Robert Chang
Try adding -lm
Eg: gcc -o foo foo.c -lm