How to reset allocated memory and resources in c?

Question

My program consists of a Menu, where you can select 1 of 2 options. The second is just to exit the program. The first, however, is where you can find a specific sequence of bits that you choose, in a separate ".txt" file with 100.000 lines.

It does what I want the first time, and then returns to the Menu.

The problem is when the user goes for a second (or more) search. The program prints on screen random information. It seems like I didn't do a "reset" of the resources, memory or values on the first search.

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

typedef struct{

    char ID[8];
    char content[2048];
    int distance;

} DATA;

void search(){

    FILE *f;
    DADO *z=NULL;
    long int tot=0;
    int a;
    int c;
    int i;
    int j=1;
    int k=0;
    char e;
    char b[2048];

    printf("\n");

    f=fopen("DANGER_DB_LARGE.txt", "r");

    printf("\n");
    printf("How many results do you wish?\n");
    scanf("%d",&a);

    printf("Introduce the sequence:\n");
    scanf("%s",b);
    c=strlen(b);

    printf("\n");

    z=(DATA*)realloc(z,(++tot)*sizeof(DATA));

    while(e!=EOF){
        e=fgetc(f);

        if(k<8){
            z[tot-1].ID[k]=e;           
        }
        else if(k==8 && e=='\t'){
            continue;
        }
        else if(k>=9 && e!='\n'){
            z[tot-1].content[k-9]=e;
        }
        else if(e=='\n'){
            k=(-1);
            z=(DATA*)realloc(z,(++tot)*sizeof(DATA));
        }
        k++;
    }

    for(i=1; i<=tot; i++){
        distance(z,i,c,b);
    }

    free(z);
    fclose(f);
}

I proceed to store the ID and content of every single one of those 100.000 lines of text. I end the function by doing free(z), but when I search again the program just prints random stuff.

Answer 1

Use of uninitialised variables without an intervening assignment is undefined behaviour. It may work on the first Wednesday of every month, on the first time through the loop, only when the boss is looking, ...

int e; // originally was char
//...
while (e != EOF) { // uninitialised, no intervening assignment