Thread: Linking library problem

Hi
I have copied the following C program (err.c) from a book and attempted to compile it.

I use the following command line protocol:

gcc –lm err.c –o err

When I do I get the following error:

/usr/lib/gcc/i386-redhat-linux/4.1.1/../../../crt1.o: In function `_start':
(.text+0x18): undefined reference to `main'
/tmp/cckvrV7Z.o: In function `rtnewt':
err.c.text+0x6e): undefined reference to `nrerror'
err.c.text+0x9d): undefined reference to `nrerror'
collect2: ld returned 1 exit status

It appears to be a “linking” problem, but I am linking the math libraries. I have no problems with sin, cos etc. It is only when the `nrerror` shows up in the script that I start getting problems with compilations.

Thanks, Steve

Hi
Here is the code:

Code:

/*The Newton Raphson C program*/

#include <math.h> 
#define JMAX 20

float rtnewt(void(*funcd)(float,float *, float * ), float x1, float x2, float xacc)
{
  void nrerror (char error_text[]);
  int j;
  float df,dx,f,rtn;

  rtn=0.5*(x1+x2);
  for (j=1;j<=JMAX;j++) {
      (*funcd)(rtn, &f,&df);
      dx=f/df;
      rtn -=dx;
      if((x1-rtn)*(rtn-x2) < 0.0)
        nrerror("Jumped out of brackets in rtnewt");
      if (fabs(dx) < xacc) return rtn;
     }
     nrerror("Maximum number of interations exceeded in rtnewt");
     return 0.0;
}

Any help would be greatly appreciated!! I have looked online at FAQ but so, far there has been no help.

Thanks
Steve

I found that the function nrerror() is part of a utility program in nrutil.c but I don't know how to implement it in compilation and add to script. Can you inform me how to do this?

Thanks for your response!!

Steve

Thanks Elysia.
Your comments were very helpful!!
Cheers,
Steve