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POUndefined reference to function - Learning C
 

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    <p>I'm learning C by translating some of the things I have done in Python to C. I have tried to look online as much as I can before coming here but it seems really difficult to find answers to what I'm looking for.</p> <p>What follows is my (so-far) translation of the Miller-Rabin test for a number's primality.</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;math.h&gt; _Bool prime(long long n); int main() { int i = 6; for (i; i &lt; 9; i++) { if (prime(i)) { printf("%i\n", prime(i)); } } } _Bool prime(long long n) { int s = 0; int r = 0; int a_index = 0; // printf("the value of a_index when initialised is: %d\n", a_index); // printf("the value of s when initialised is: %d\n", s); int *a_list; _Bool is_prime = 1; _Bool composite_part_a = 1; _Bool composite_part_b = 1; long long d = n - 1; while (d % 2 == 0) { s++; d = d / 2; } if (4759123141 &lt;= n &amp;&amp; n &lt; 2152302898747) { // malloc a_list[0] = 2; a_list[1] = 3; a_list[2] = 5; a_list[3] = 7; a_list[4] = 11; } else if (9080191 &lt;= n &amp;&amp; n &lt; 4759123141) { // malloc a_list[0] = 2; a_list[1] = 7; a_list[2] = 61; } else if (1373653 &lt;= n &amp;&amp; n &lt; 9080191) { // malloc a_list[0] = 31; a_list[1] = 73; } else if (4 &lt;= n &amp;&amp; n &lt; 1373653) { a_list = (int *) malloc(sizeof(int) * 2); a_list[0] = 2; a_list[1] = 3; printf("the value of a_list[0] upon its first assignment is: %d\n", a_list[0]); // printf("the first element of a_list is: %d\n", a_list[0]); // printf("the second element of a_list is: %d\n", a_list[1]); } else if (n == 3 | n == 2) { return 1; } else if (n % 2 == 0 | n == 1) { return 0; } printf("the value of a_list[0] over here is: %d\n", a_list[0]); // printf("%d\n", a_list[1]); for (a_index; a_index &lt; sizeof(a_list) / sizeof(int); a_index++) { printf("test"); if ((long long)pow(a_index[a_list], d) % n != 1) { composite_part_a = 1; } else { composite_part_a = 0; } // printf("the value of r is: %d\n", r); // printf("the value of s is: %d\n", s); for (r; r &lt; s; r++) { printf("%lld\n", (int)pow(a_list[a_index], exp2(r) * d) % n); if ((long long)pow(a_index[a_list], exp2(r) * d) % n != -1) { composite_part_b = 1; } else { composite_part_b = 0; break; } } if (composite_part_a &amp;&amp; composite_part_b) { return 0; } } return is_prime; } </code></pre> <p>The trouble with learning C is there isn't much good literature for pure beginners, outside of what I hear about K&amp;R but that's in the mail and I can't get my hands on it right now. The program returns these errors:</p> <pre><code>3.c: In function ‘prime’: 3.c:52:26: warning: incompatible implicit declaration of built-in function ‘malloc’ [enabled by default] /tmp/ccGQnk9T.o: In function `prime': 3.c:(.text+0x272): undefined reference to `pow' 3.c:(.text+0x2b9): undefined reference to `exp2' 3.c:(.text+0x2db): undefined reference to `pow' 3.c:(.text+0x30b): undefined reference to `exp2' 3.c:(.text+0x32d): undefined reference to `pow' collect2: ld returned 1 exit status </code></pre> <p>First off, haven't I included to introduce pow and else? I know it's not proper to ask two questions and my main question is about pow and exp2, but if you do have a suggestion about the malloc as well feel free to include it.</p>
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    1. COIt is not your program executable, it is the `gcc` compiler (and linker) which returns the "undefined reference" errors.
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      1. USBasile Starynkevitch
 

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