Thread: program adding numbers using desired base doesn't show any output

Hello, I have a problem with an "add calculator".
Valgrind reports no memory errors, no errors from compiler but the program doesn't show any output despite the printf - "Result is zero".

All pointers, and variables are (n my opinion) correctly initialized.
getnum function gets a number, returns a pointer to char *,
add function processes two numbers as strings, returns result which is a pointer to char (char *) as well.

Trying to work it out for the past 4 hours and can't find a mistake.
Thanks in advance!

Here's the code (sorry, it's quite long):

Code:

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>

#define MAX(A,B) ((A)>(B) ? (A) : (B))

char *getnum(FILE *infile, int base)
{
    int len = 10;
    int c;
    int pos = 0;
    char *num = NULL; 
    char *tmpnum = NULL;
    
    num = malloc(sizeof(char)*len);
    if(num == NULL) {
        perror("malloc fail");
        return NULL;
    }
    while (((c = fgetc(infile)) != EOF) && (isalnum(c))) {
        num[pos++] = c;
        if (isdigit(c)) {
            if (c >= base + '0') {
                fprintf(stderr, "Wrong base\n");
                free(num);
                return NULL;
            }
        }
        else if (isalpha(c)) {
            if ( c >= base + '0' + 7) {
                fprintf(stderr, "Wrong base, expected 16\n");
                free(num);
                return NULL; 
            }
        }
        if (pos >= len) {
            len *= 2;
            tmpnum = realloc(num, len*sizeof(char));
            if (tmpnum == NULL) {
                perror("realloc fail");
                free(num);
                return NULL;
            }
            else num = tmpnum;
        }
    }
    num[pos] = '\0';
    return num;            
}

char *add(char *no1, char *no2, int base)
{
    int len1, len2, length, i, j, pos, adder = 0;
    char *result = NULL; 
    char *tmp1 = NULL;
    char *tmp2 = NULL;
    
    len1 = strlen(no1);
    len2 = strlen(no2);
    length = MAX(len1, len2);
    if (len1 == 1 && len2 == 1) {
        length++;
    }    
    result = malloc((length + 1)*sizeof(char));
    if (result == NULL) {
        perror("malloc fail");
        free(result);
        return NULL;
    }
    tmp1 = realloc(no1, (length + 1)*sizeof(char));             
    if (tmp1 == NULL) {
        perror("realloc fail");
        free(result);
        return NULL;
    } else {
        no1 = tmp1;
    }
    tmp2 = realloc(no2, (length + 1)*sizeof(char));                
    if (tmp2 == NULL) {
        perror("realloc fail");
        free(result);
        free(no1);
        return NULL;
    } else {
        no2 = tmp2;
    }
    for (i = length - 1, j = len1 - 1; j >= 0; i--, j--) {
        no1[i] = no1[j];
    }
    for (i = 0; i < (length - len1); i++) {
        no1[i] = '0';
    }
    no1[length] = '\0';

    for (i = length - 1, j = len2 - 1; j >= 0; i--, j--) {
        no2[i] = no2[j];
    }
    for (i = 0; i < (length - len2); i++) {
        no2[i] = '0';
    }
    no2[length] = '\0';
    
    pos = length - 1;
    
    while (pos >= 0) {
        if (no1[pos] > '9') {
            no1[pos] -=7;
        }            
        if (no2[pos] > '9') {
            no2[pos] -=7;
        }
        result[pos] = no1[pos] + no2[pos] + adder - '0';
        adder = 0;
        if (result[pos] >= (base + '0')) {
            result[pos] -= base;
            adder = 1;
        }
        if (result[pos] > '9') {
            result[pos] += 7;
        }
        pos--;
    }
    result[length] = '\0';
    free(no1);
    free(no2);
    return result;
}    
    
int main(int argc, char **argv)
{
    FILE *infile = NULL;
    char *number1 = NULL;
    char *number2 = NULL;
    char *result = NULL;
    int base, i, j = 0, length, count = 0;
    
    if (argc != 3) {
        printf("usage: ./add infile.txt base\n");
        return -1;
    }
    infile = fopen(argv[1], "r");
    if (infile == NULL) {
        perror("infile open failed");
        return -1;
    }
    base  = atoi(argv[2]);
    while (!feof(infile)) {
        number1 = getnum(infile, base);
        if (number1 == NULL) {
            fclose(infile);
            return -1;
        }
        number2 = getnum(infile, base);
        if (number2 == NULL) {
            fclose(infile);
            free(number1);
            break;                             /* or return ? */
        }                
        break;
    }
    printf("Base is %d\n", base);
    result = add(number1, number2, base);
    if (result == NULL) {
        free(number1);
        free(number2);
        fclose(infile);
        return -1;
    }
    length = strlen(result);
    for (i = 0; i <= length - 1; i++) {
        if (result[i] == '0') {
            count++;
        }
    }
    if (count == length) {
        printf("Result is 0\n");
        free(result);
        result = NULL;                     /* arguable */
        fclose(infile);
        return 0;
    }
    for (i = 0; i <= length - 1; i++) {
        if (result[i] != '0') {
            break;
        }
    }
    for (j = i; j == (length - 1); j++) {
        printf("Result is: %s\n", &result[j]);
        break;
    }
    free(result);
    result = NULL;
    fclose(infile);
    return 0;
}