What does the mean of error messages?

This is a discussion on What does the mean of error messages? within the C Programming forums, part of the General Programming Boards category; Code: #include <math.h> #include <stdio.h> #include <stdlib.h> void SpecialNumber(int n) { FILE *fw; int i, j, k, d; int *a; ...

  1. #1
    Registered User
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    Apr 2005
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    What does the mean of error messages?

    Code:
    #include <math.h>
    #include <stdio.h>
    #include <stdlib.h>
    
    void SpecialNumber(int n)
    {
    	FILE *fw;
    	int i, j, k, d;
    	int *a;
    	d = 0;
    	a = malloc(n*sizeof(*a));
    	fw = fopen("SpecialNumber.out", "wt");
    	for (i = 2; i < pow(10, n); i++) {
    		for (j = 0, k = pow(10, n); k >= 10; j++) {
    			a[k] = (int)(i%j)/(j/10);
    			j/=10;
    		}
    		for (j = 0; j < n; j++) {
    			d += pow(a[j], n);
    		}
    		if (d == i)
    			fprintf(fw, "%5d", i);
    	}
    	free(a);
    	fclose(fw);
    }
    
    int main()
    {
    	FILE *fr;
    	int n;
    	fr = fopen("SpecialNumber.dat", "rt");
    	fscanf(fr, "%d", &n);
    	SpecialNumber(n);
    	fclose(fr);
    	return 0;
    }
    Code:
    mathsniper:~# gcc -O2 -o SpecialNumber SpecialNumber.c
    /tmp/cc4zGvKf.o: In function `SpecialNumber':
    SpecialNumber.c:(.text+0x56): undefined reference to `pow'
    SpecialNumber.c:(.text+0x79): undefined reference to `pow'
    SpecialNumber.c:(.text+0xe5): undefined reference to `pow'
    collect2: ld returned 1 exit status
    I have included the math.h but it show the error messages.

  2. #2
    and the hat of wrongness Salem's Avatar
    Join Date
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    You also need to link with the math library
    Code:
    gcc prog.c -lm
    That's "minus L M" (but in lower case).
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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