My code functions with a printf statement, but not without it - c

Question

Adding the printf("Hi!\n") statements allows the code to work. It also works if the bound initial bound is improper and the user enters a new one. When I ran some tests calculate divers sometimes returned a character instead of an integer. I'm thinking it has something to do with my memory allocation. I also noticed that ./a.out 6 10 "|" would work but ./a.out 6 25 "|" would not causing an infinite loop when printing the lines of "|".
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
// Structs
typedef struct data_struct {
int lineNumber;
int divisorSum;
char type[10];
}data;
// Prototypes
int calculateDivsors(int integer);
// Functions
int main (int argc, char *argv[]) {
int lowerBound;
int upperBound;
char character;
// Gets the values from command-line
sscanf(argv[1], "%d", &lowerBound);
sscanf(argv[2], "%d", &upperBound);
sscanf(argv[3], "%c", &character);
// Check to see if bound is proper
while (upperBound <= lowerBound || lowerBound < 2) {
printf("Error, please enter a new range (positive increasing).\n");
scanf("%d %d", &lowerBound, &upperBound);
}
// Structure calls
data* info = NULL;
int totalData = upperBound - lowerBound;
// Allocate the memory
info = (data*)malloc(totalData * sizeof(data));
printf("Hi!\n");
if (info != NULL) {
// Iterate through all the digits between the two bounds
for (int i = lowerBound; i <= upperBound; i++) {
int sum = calculateDivsors(i);
// Write data to indiviual structures
info[i].lineNumber = i;
info[i].divisorSum = sum;
// Check to see if the sum is greater than, less than, or equal to the original
if (sum == i) {
strcpy(info[i].type, "Perfect");
}
else if (sum > i) {
strcpy(info[i].type, "Abundant");
}
else if (sum < i) {
strcpy(info[i].type, "Deficient");
}
// Line n# has a column width of 4, string of 10
printf("%4d is %-10s\t", info[i].lineNumber, info[i].type);
// Generate Pictogram
for (int j = 0; j < info[i].divisorSum; j++) {
printf("%c", character);
}
printf("\n");
}
}
}
// Adds up the sum of diviors
int calculateDivsors(int integer) {
int sum = 0;
for (int i = 1; i < integer; i++) {
// Add to sum if perfectly i is a sum of integer
if (integer % i == 0) {
sum += i;
}
}
return sum; // Returns the sum of diviors
}

Answer 1

You are accessing data outside its allocated buffer whenever lowerBound doesn't start with 0.
info[i].lineNumber = i;
Ideally, you should become...
info[i - lowerBound].lineNumber = i;
To ensure that the indexing starts at 0. Further, your window between lowerBound and upperBound is inclusive. That means it includes both ending boundaries. Therefore, totalData is undersized by one element. Even if you fix the indexing problem, your code will still be wrong with this:
int totalData = (upperBound - lowerBound) + 1;
Failing to do both of the above causes your code to invoke undefined behavior (UB), and thus unpredictable results thereafter. It may even appear to work. That, however, is a red herring when your code has UB. Don't confuse defined behavior with observed behavior. You can trust the latter only once you have the former; the two are not synonymous.