Thread: segmenation fault when executing

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/time.h>
#include <math.h>
#include <string.h>

// Sockets includes.
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>



// Constants
#define HOSTLEN 256
#define BUFLEN 40960
#define CMDLEN 256

// Cache data structures from websurf.c
char* cache;
int cache_size = 0;
int num_compacts = 0;   // Spread number of compactions over total sites visited.

struct node
{
	char webpage[80];
	int space;
	int buddy_index;
	int status;
};

struct partition
{
	struct node *heap;
	int part_length;
	int blockSize;	
};

int cache_space=64;
struct partition *mem;
int mem_length;

char **siteList;
char domain[HOSTLEN];
int numSites=0;

int websurf(int argc, char **argv);
int browse(char* host, char* page, int id);
void createCache();
int cacheWebpage(int index, int size);
void readWebpages(char* urls);
int putWebpage();
int memorySpace(int sizeOfWebpage);
int main()
{	
	char* surf_arg[9];
	int x; int page_size; int page_index;
	srand((unsigned)time(NULL));
	surf_arg[0]="";
        surf_arg[1]="-f";
        surf_arg[2]="my_url.txt";
        surf_arg[3]="-s";
        surf_arg[4]="1";
        surf_arg[5]="-n";
        surf_arg[6]="1";
        surf_arg[7]="-c";
        surf_arg[8]="1";
	createCache();
        readWebpages("urls.txt");
	printf("****************************************************************************\n");
	for(x=0; x<1; x++)
	{
		page_index=putWebpage();
		page_size=websurf(9,surf_arg);
		printf("page_size: %d\n",page_size);
	//	cacheWebpage(page_index, page_size);
		printf("****************************************************************************\n");
	}
	
	for(x=0; x<mem_length; x++)
        {
                printf("%d\n",mem[x].part_length);
        }

	return 0;
}

void createCache()
{
	int num_elements=1;
	int x; int y; int temp_size=cache_space;
	for(x=1; x<cache_space; x=x*2)
	{
		num_elements++;
	}
	mem_length=num_elements;
	struct partition *mem=(struct partition*)calloc(mem_length,sizeof(struct partition));
	for(x=0; x<mem_length-1; x++)
	{
		mem[x].heap=(struct node*)calloc(temp_size,sizeof(struct node));
		mem[x].blockSize=(int)pow((double)2,(double)x);
		mem[x].part_length=temp_size;
		for(y=0; y<mem[x].part_length; y++ )
		{
			mem[x].heap[y].buddy_index=y+1;
			mem[x].heap[y].status=0;
			y++;
			mem[x].heap[y].buddy_index=y-1;
			mem[x].heap[y].status=0;
		}
		temp_size=temp_size/2;	
	}
	mem[mem_length-1].heap=(struct node*)calloc(1,sizeof(struct node));
	mem[mem_length-1].blockSize=cache_space;
	mem[mem_length-1].part_length=1;
	mem[mem_length-1].heap[0].buddy_index=-1;
}

int cacheWebpage(int index, int size)
{
	int x; int ins;
	int sizeOnCache=memorySpace(size); 
	if(sizeOnCache>cache_space)
		return -1;
	printf("page: %s, size: %d, sizeoncache: %d\n",siteList[index],size,sizeOnCache);
	printf("mem_length: %d\n",mem_length);
}

void readWebpages(char* urls)
{
	int s;
	FILE *stream;
	stream=fopen(urls,"r+");
	fscanf(stream,"%i %s\n",&numSites,domain);
	siteList=(char**)calloc(numSites,sizeof(char*));
	for(s=0; s<numSites; s++)
	{
		siteList[s] = (char*)calloc(HOSTLEN, sizeof(char));
		fscanf(stream,"%s\n",siteList[s]);
	}		
}

int putWebpage()
{
	FILE* stream = fopen("my_url.txt","w");
	int ran_site_index=0;
	ran_site_index=(rand() % 30);
	fprintf(stream,"%d %s\n",1,domain);
	fprintf(stream,"%s\n",siteList[ran_site_index]);
	fclose(stream);
	return ran_site_index;
}

int memorySpace(int sizeOfWebpage)
{
	int powerOfTwo=1;
	while(powerOfTwo<sizeOfWebpage)
		powerOfTwo*=2;
	return powerOfTwo;
}

int websurf(int argc, char **argv) 
{
	// Program arguments
	int s, num_websites = 0, page_index; int page_size;
	char filename[HOSTLEN];
	FILE* fp;
	struct timeval tval;
	struct timezone tzone;
	// Web host and pages
	char host[HOSTLEN];
	char **pages;
	int num_pages = 0;
	// Get program arguments.
	for (s=1; s<argc; s++) {
		// Filename
		if ((strcmp (argv[s],"-f")) == 0) {
			s++;
			strcpy (filename, argv[s]);
		}
		// Number of compactions
		else if ((strcmp (argv[s],"-c")) == 0) {
			s++;
			num_compacts = atoi (argv[s]);
		}
		// Number of websites to randomly visit
		else if ((strcmp (argv[s],"-n")) == 0) {
			s++;
			num_websites = atoi (argv[s]);
		}
		// Cache size
		else if ((strcmp (argv[s],"-s")) == 0) {
			s++;
			cache_size = atoi (argv[s]);
		}
		// Print usage
		else {
			printf ("Usage: ./websurf -f <filename> -s <queue size> -n <# websites to visit> -c <# of compactions>\n");
			exit (0);
		}
	}
	// Print program arguments
	printf ("Filename: %s\n", filename);
	printf ("Number of websites to access = %i\n", num_websites);
	printf ("Cache size = %i\n", cache_size);
	printf ("Number of times to compact memory = %i\n", num_compacts);
	// Open file and store host and page names into pages array.
	fp = fopen (filename, "r+");
	if (fp == NULL) {
		printf ("Error - could not open URLs file\n");
		exit (-1);
	}
	fscanf (fp, "%i %s\n", &num_pages, host);
	pages = (char**) calloc (num_pages, sizeof(char*));
	for (s=0; s<num_pages; s++) {
		pages[s] = (char*) calloc (HOSTLEN, sizeof(char));
		fscanf (fp, "%s\n", pages[s]);
		//printf ("URL: %s%s\n", host, pages[s]);
	}
	// Seed random number generator
	gettimeofday (&tval, &tzone);
	srand48 (tval.tv_usec);
	// Start browsing randomly in list of available pages.
	for (s=0; s<num_websites; s++) {
		page_index = (int)(ceil(drand48() * (float)num_pages)) - 1;  // Get random page index.
		printf ("Page index %i URL: %s%s\n", page_index, host, pages[page_index]);
		page_size=browse (host, pages[page_index], page_index);
	}
	return page_size; 
} 
/**********************************************************************************/ 
// Main function where host and page names are initialized, and threads are created. 
int browse (char* host, char* page, int id) {
	//Socket data structures - Need only 1 socket to browse many pages.
	int sckt;
	struct hostent *he;
	struct sockaddr_in srvaddr;
	char cmd[CMDLEN];  // Command line to send to web server
	// Webpage data structures
	int nread;
	char buf[BUFLEN];
	char *body;
	int temp_fd;
//	int child;
//	int result;
	char tempfilename[16];
	int webpage_size = 0; // Initialize page size to 0
	
	// Child process
//	int pid;
	
	// create TCP connection to web server
	if ((sckt = socket(AF_INET, SOCK_STREAM, 0)) == -1)
		perror("socket"), exit(1);
	if ((he = gethostbyname(host)) == NULL)
		perror("gethostbyname"), exit(1);
	//bzero(&srvaddr, sizeof(srvaddr));
	srvaddr.sin_family = AF_INET;
	srvaddr.sin_addr.s_addr = *(int *)(he->h_addr_list[0]);
	srvaddr.sin_port = htons (80);
	if (connect(sckt, (struct sockaddr *)&srvaddr, sizeof(srvaddr)) == -1)
       		perror("connect"), exit(1);
	// create GET request
	sprintf(cmd, "GET %s HTTP/1.1\r\nHost: %s\r\n\r\n", page, host);
	printf ("cmd: %s\n", cmd);
	// send GET request
	if (write(sckt, cmd, strlen(cmd)) != strlen(cmd))
		perror("GET write"), exit(1);
	// read response
	if ((nread = read(sckt, buf, BUFLEN)) < 0)
		perror("read"), exit(1);
	if (nread >= BUFLEN)
		fprintf(stderr, "web: need bigger (HTTP) read buffer\n"), exit(1);
	buf[nread] = 0;
	printf("web: nread = %d\n", nread);
	if (nread < 512) printf("web: response: %s\n", buf);
	else printf("web: initial chars of response: %.300s\n", buf);
	// check return code
	//if (strncmp(buf, "HTTP/1.1 200 OK", 15))
	// fprintf(stderr, "web: GET failed\n"), exit(1);
	// bail out if chunked encoding
	if (strstr(buf, "Transfer-Encoding: chunked")) {
		fprintf(stderr, "web: can't handle chunked encoding\n");
		//pthread_exit(NULL);
		exit (0);
	}
	// trim HTTP protocol header from response
	if ((body = strstr(buf, "\r\n\r\n")) == NULL)
		fprintf(stderr, "web: can't find end of HTTP header in response\n"), exit(1);
	body = body + 4;
	// create & open temp file
	sprintf(tempfilename, "temp%i.html", id);
	temp_fd = open (tempfilename, O_CREAT | O_RDWR | O_TRUNC, S_IRWXU);
	// if server sent only header: read further response & dump in a loop
	webpage_size = 0; // Initialize page size to 0
	if (body-buf >= nread) {
		do {
			if ((nread = read(sckt, buf, BUFLEN)) < 0)
				perror("read"), exit(1);
			else if (nread == 0) break;
			if (nread >= BUFLEN)
				fprintf(stderr, "web: need bigger (HTTP) read buffer\n"), exit(1);
			if (write(temp_fd, buf, nread) != nread)
				perror("file write"), exit(1);
			webpage_size += nread; // Accumulate page size.
		} while (nread > 0);
		close(temp_fd);
	}
	// if server sent header & some body: assume it's the whole page & dump it into file
	else {
		webpage_size = strlen(body);
		if (write(temp_fd, body, strlen(body)) != strlen(body))
			perror("file write"), exit(1);
		close(temp_fd);
	}
	
	// Print out size of webpage content
	//printf ("Webpage size %i \n", (webpage_size/1024)+1);
	return((webpage_size/1024)+1);
	// Fork off process to display webpage.
	/* pid = fork ();
	printf ("Process id %i\n", pid);
	if (pid == 0) {
		// Run Lynx
		if (execl("/opt/gnu/bin/lynx", "/opt/gnu/bin/lynx", tempfilename, NULL) < 0)
			perror("execl"), exit(1);
		// Better to run netscape if possible
		//if (execl("/usr/local/bin/netscape", "/usr/local/bin/netscape", tempfilename, NULL) < 0)
		// perror("execl"), exit(1);
	}
	else {
		printf ("After forking child process, parent process will now start writing to the file descriptor (pipe or file).\n");
	} */ 
}

i keep getting a segmentation fault when i try to access the array mem outside of the function createCache(). In the function i allocate all the space and initialize the variables that i need. I created mem as a public variable. When the code executes the for loop at the very end of main it gets a segmentation fault.

i got it nevermind

good because there is no way anyone is just going to look through all that code for you.
next time use a debugger and at least point out a section of code that the problem would possibly be in.