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Why is <code>intAlloc</code> not returning int* ? <pre><code>int *intAlloc(int amount) { int *ptr; ptr = (int *)malloc(amount * sizeof(int)); if(ptr == NULL) { printf("Error: NULL pointer\n"); exit(1); } return ptr; //like this } </code></pre> EDIT (after your update): On <code>atkinsPrimes()</code> where is filtered being intAlloc()ed? <pre><code>int *atkinsPrimes(int limit) { int *primes; int *initialPrimes; int *filtered; int *results; int resultsSize; primes = intAlloc(limit+1); // ... initialPrimes = intAlloc(2); // ... resultsSize = counter + trueCount(primes, limit+1); free(primes); free(initialPrimes); free(filtered); // Where was it intAlloc()ed? results[resultsSize] = 0; // make the array 0-terminated to make it easier to work with return results; } </code></pre> EDIT (after your N-th update): This is a compilable version of your code. It ran smooth on my machine, no crashes. Compiled with g++ (due to declarations of variables inside the for statement): g++ (Debian 4.3.2-1.1) 4.3.2 <pre><code>#include <stdio.h> #include <stdlib.h> #include <math.h> int *goldbachPartition(int x); int *atkinsPrimes(int limit); int trueCount(int *subject, int arraySize); int intCount(int *subject) ; void intFillArray(int *subject, int arraySize, int value); int *intFilterArrayKeys(int *subject, int arraySize); int *intAlloc(int amount); void printOutput(int num1, int num2, int rep) ; int *intMergeArrays(int *subject1, int *subject2, int arraySize1, int arraySize2); int main(int argc, char **argv) { if (argc < 3) { printf("Usage: ./program <lower> <upper>\n"); return 0; } int *partition; int lowerLimit = atoi(argv[1]); int upperLimit = atoi(argv[2]); // snip ... got lowerLimit and upperLimit from console arguments // this is the 'main loop': for (int i = lowerLimit; i <= upperLimit; i += 2) { partition = goldbachPartition(i); printOutput(partition[0], partition[1], i); free(partition); // I get problems on the second iteration here } return 0; } int *goldbachPartition(int x) { int solved = 0; int y, z; int *primes; int *result; result = intAlloc(2); primes = atkinsPrimes(x); for (int i = intCount(primes)-1; i >= 0; i--) { y = primes[i]; for (int j = 0; j < y; j++) { z = primes[j]; if (z + y >= x) { break; } } if (z + y == x) { solved = 1; result[0] = y; result[1] = z; break; } else if (y == z) { result[0] = 0; result[1] = 0; break; } } free(primes); return result; } int *atkinsPrimes(int limit) { int *primes; int *initialPrimes; int *filtered; int *results; int counter = 0; int sqrtLimit; int xLimit; int resultsSize; primes = intAlloc(limit+1); intFillArray(primes, limit+1, 0); sqrtLimit = floor(sqrt(limit)); xLimit = floor(sqrt((limit+1) / 2)); for (int x = 1; x < xLimit; x++) { int xx = x*x; for (int y = 1; y < sqrtLimit; y++) { int yy = y*y; int n = 3*xx + yy; if (n <= limit && n % 12 == 7) { primes[n] = (primes[n] == 1) ? 0 : 1; } n += xx; if (n <= limit && (n % 12 == 1 || n % 12 == 5)) { primes[n] = (primes[n] == 1) ? 0 : 1; } if (x > y) { n -= xx + 2*yy; if (n <= limit && n % 12 == 11) { primes[n] = (primes[n] == 1) ? 0 : 1; } } } } for (int n = 5; n < limit; n++) { if (primes[n] == 1) { for (int k = n*n; k < limit; k += n*n) { primes[k] = 0; } } } initialPrimes = intAlloc(2); if (limit >= 2) { initialPrimes[counter++] = 2; } if (limit >= 3) { initialPrimes[counter++] = 3; } filtered = intFilterArrayKeys(primes, limit+1); results = intMergeArrays(initialPrimes, filtered, counter, trueCount(primes, limit+1)); resultsSize = counter + trueCount(primes, limit+1); free(primes); free(initialPrimes); free(filtered); results[resultsSize] = 0; return results; } int trueCount(int *subject, int arraySize) { int count = 0; for (int i = 0; i < arraySize; i++) { if (subject[i] == 1) { count++; } } return count; } int intCount(int *subject) { // warning: expects 0 terminated array. int count = 0; while (*subject++ != 0) { count++; } return count; } void intFillArray(int *subject, int arraySize, int value) { for (int i = 0; i < arraySize; i++) { subject[i] = value; } } int *intFilterArrayKeys(int *subject, int arraySize) { int *filtered; int count = 0; filtered = intAlloc(trueCount(subject, arraySize)); for (int i = 0; i < arraySize; i++) { if (subject[i] == 1) { filtered[count++] = i; } } return filtered; } int *intMergeArrays(int *subject1, int *subject2, int arraySize1, int arraySize2) { int *merge; int count = 0; merge = intAlloc(arraySize1 + arraySize2); for (int i = 0; i < arraySize1; i++) { merge[count++] = subject1[i]; } for (int i = 0; i < arraySize2; i++) { merge[count++] = subject2[i]; } return merge; } int *intAlloc(int amount) { int *ptr; ptr = (int *)malloc(amount * sizeof(int)); if (ptr == NULL) { printf("Error: NULL pointer\n"); } return ptr; } void printOutput(int num1, int num2, int rep) { if (num1 == 0) { printf("%d: No solution\n", rep); exit(0); } else { printf("%d = %d + %d\n", rep, num1, num2); } } </code></pre> Since you are still omitting some source, I can only imagine that the problem is hidden there. EDIT: (my last update) To assist your debugging, you should replace your main() function by the one below: <pre><code>int main(int argc, char **argv) { int *primes = NULL; primes = atkinsPrimes(44); // Evil magic number free(primes); return 0; } </code></pre> Having a minimal example to reproduce the behavior you pointed out is much better then the whole thing. Have fun with atkinsPrimes(44)
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