Segmentation fault using DS18B20 Temperature Sensor - c++

Question

I am trying to run a code in C++ that takes the reading from raspberry pi3 using DS18B20 . The code is compiled without errors but when i try to run it . It gives an error of segmentation fault .
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <wiringPi.h>
#include <iostream>
#define BUFSIZE 128
using namespace std;
int main(void)
{
float temp;
int i, j;
size_t ret;
FILE *fd;
char buf[BUFSIZE];
char tempBuf[5];
char *buffer;
buffer = (char*) malloc (sizeof(char)*BUFSIZE);
while(1){
fd = fopen("/sys/bus/w1/devices/28-0000085c3551/w1_slave", O_RDONLY);
if(fd != NULL){
perror("open device file error");
break;
}
while(1){
ret = fread(buffer, sizeof(char), BUFSIZE, fd);
if(0 == ret){
break;
}
if(-1 == ret){
if(errno == EINTR){
continue;
}
std::cout<<"Read Error";
fclose(fd);
break;
}
}
for(i=0;i<sizeof(buf);i++){
if(buf[i] == 't'){
for(j=0;j<sizeof(tempBuf);j++){
tempBuf[j] = buf[i+2+j];
}
}
}
temp = (float)atoi(tempBuf) / 1000;
std::cout<< "%.3f C\n" << temp;
fclose(fd);
//delay(500);
}
}
`
In compiling no errors occcurs .
it(stackoverflow site) kept on asking to to add more details i have no more details to add this is the only problem i am facing and the above code is compiling but not running .Hopefully some of you can help

Answer 1

The second argument to the fopen() call must be a string, in your case it should be "r" to open the file in read-only mode
fopen() returns NULL if the file couldn't be opened, and a non-NULL pointer otherwise; your code that checks if (fd != NULL) should check if (fd == NULL) instead
As pointed out in a comment to your question, the expression buf[i+2+j] could access a location outside the buf array
tempBuf isn't guaranteed to have a string terminator character in it, so when you call atoi(tempBuf) this function could access past the end of the tempBuf array