[SOLVED] Segmentation fault in C program

why_so_serious · 10-25-2013, 12:49 AM

Code:

#include <sys/socket.h>
#include <sys/types/h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <uniistd.h>
#include <errno.h>
#include <arpa/net.h>

int main (void)
{
	int sockfd, n;
	struct sockaddr_in serv_addr;
	struct hostent *server;
	
	char buffer[256];
	char hostname[1024];
	struct hostent *h;
	gethostname(hostname, sizeof(hostname));
	server = gethostbyname(hostname);
	sockfd = socket(AF_INET, SOCK_STREAM, 0);
	if (sockfd < 0)
	error("ERROR opening socket");
	if(server == NULL)
	{
		fprintf(stderr, "Error no such host\n");
		exit 0;
	}
	bzero((char ) &serv_addr, sizeof(serv_addr));
	serv_addr.sin_family = AF_INET;
	memcpy(&serv_addr.sin_addr, server->h_addr, server->h_length);
	bcopy((char *)server->h_addr,(char *)&serv_addr.sin_addr.s_addr,server->h_length);
	serv_addr.sin_port = htons (SERVERPORT);
	if(connect(sockfd, (struct sockaddr *)&serv_addr, sizeof (serv_addr)) < 0) 
	error ("ERROR connecting");
	printf("Please enter the message: ");
	bzero(buffer, 256);
	fgets(buffer,255,stdin);
	n = write(sockfd, buffer, strlen(buffer));
	if (n < 0)
	error ("ERROR writing to socket");
	bzero(buffer, 256);
	n = read (sockfd, buffer, 255);
	if (n < 0)
	error ("ERROR reading from socket");
	printf("here we are %s\n", buffer);
	close(sockfd);
}

Hi everyone, I am a bit newbie and Linux. When I run above program, I got an error like "segmentation fault". Why it is so? if anyone knows, pls kindly guide me.

thanks a lot

pan64 · 10-25-2013, 12:52 AM

there is no such error (like segmentation fault).
Try to use debug info, debug your code step by step or try to use valgrind to catch the problem. You can even try to analyze the coredump.

why_so_serious · 10-25-2013, 12:54 AM

Quote:

Originally Posted by pan64

there is no such error (like segmentation fault).
Try to use debug info, debug your code step by step or try to use valgrind to catch the problem. You can even try to analyze the coredump.

Hi thanks for your reply. But how to use debug info. Now I am using Geany as my ide. I am a bit new to all those. So sorry for my stupid question. And thanks for your understanding...

pan64 · 10-25-2013, 01:03 AM

In geany Build -> Set Build Commands -> modify the gcc command, add -g to both Compile and Build

why_so_serious · 10-25-2013, 01:09 AM

I still got same error even though I use gdb.

why_so_serious · 10-25-2013, 01:12 AM

Quote:

Originally Posted by pan64

In geany Build -> Set Build Commands -> modify the gcc command, add -g to both Compile and Build

Means behind the

Code:

gcc -Wall -c "%f" -g

and

Code:

gcc -Wall -o "%e" "%f" -g

????

I think behind gcc -Wall -g???

pan64 · 10-25-2013, 01:22 AM

that is ok, -Wall -g should also work. Surely it will not solve the issue but will generate additional information to help to solve this problem.
you will have a result, a program and you can try gdb <your program> to debug it. (better to try ddd, it has a nice gui)
but first you need to check if the compilation/building gave you warnings and you need to try to eliminate them.