I’m encountering an issue while reading an file that contains records with length indicators and fields separated by ‘|’. In this program, I’m reading information about the quantity and price of a product and summing them up. However, when I attempt to use realloc() for my buffer variable, I encounter unexpected behavior. Strangely, the result I’m expecting is 118.239998, but when I use realloc(), the result becomes 118.275002. Surprisingly, when I use free(buffer) and then allocate memory again using malloc() for the buffer, I get the correct result.

This is the file
The first byte serves as a length indicator, and both ‘n'(10 in decimal) and ‘NL'(13 in decimal) also serve as indicators.

OUTPUT WITH FREE + MALLOC

OUTPUT WITH REALLOC

here is my code:

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

int main() {
    char *buffer, *produto;
    int tamRegistro, quantidade;                                                
    float preco, total = 0;
    FILE* arquivo;
  
    arquivo = fopen("compras.txt", "r");

    if (arquivo == NULL) {
        printf("Erro ao abrir o arquivon");
        system("pause");
        exit(1);
    }
    //take the first length indicator 
    tamRegistro =fgetc(arquivo);
    buffer = (char*)malloc(sizeof(char) * tamRegistro);
  
    if (buffer == NULL) {
        printf("Falha ao alocar  memorian");
        exit(1);
    }
   
    while (fread(buffer, tamRegistro, 1, arquivo) == 1) {
        //separate fields
        printf("LENGTH:%d-", tamRegistro);
        produto = strtok(buffer, "|");
        printf("%s-", produto);         
        quantidade = atoi(strtok(NULL, "|"));
        printf("%d-", quantidade);
        preco = atof(strtok(NULL, "|"));
        printf("%f-n", preco);
    
        total += (preco * quantidade);
        //take next length indicator
        tamRegistro = fgetc(arquivo);
        *buffer=(char*)realloc(buffer,sizeof(char)*(tamRegistro));  
    }
    
    free(buffer)
    fclose(arquivo);
    printf("%fn",total);
  
    return 0;
}