Question

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 – “Base is “.

All pointers, and variables are (n my opinion) correctly initialized.

getnum function gets a number, returns a pointer to char – char *,
add function processes two numbers as strings, returns result which is a pointer to char (char *) as well.

I don’t know whether the problem is memory allocation or procedures connected to processing arrays…

Here’s the 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);

    while (((c = fgetc(infile)) != EOF) && (isalnum(c))) {

        if (isdigit(c)) {
           /* irrelevant*/
        }
        else if (isalpha(c)) {
            fprintf(stderr, "Wrong base, expected 16\n");
            free(num);
            return NULL;

        }
        if (pos >= len) {
            /*realloc*/
        }
    }

    return num;           
}

---

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;


    infile = fopen(argv[1], "r");

    base  = atoi(argv[2]);
    while (!feof(infile)) {
        number1 = getnum(infile, base);

        number2 = getnum(infile, base);

        break;
    }
    printf("Base is %d\n", base);
    result = add(number1, number2, base);

    length = strlen(result);
    for (i = 0; i <= length - 1; i++) {
        if (result[i] == '0') {
            count++;
        }
    }

    for (j = i; j == (length - 1); j++) {
        printf("Result is: %s\n", &result[j]);
        break;
    }
    free(result);
    result = NULL;
    fclose(infile);
    return 0;
}

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

Answer 1

There is one severe typo near the end of main().

for (j = i; j == (length - 1); j++) {
/*            ^^ SHOULD BE <= */
    printf("Result is: %s\n", &result[j]);
    break;
}