problem with dynamic memory using malloc

[suhassr]

hi guys actually i was wondering if u could help me out with this code as soon as possible

#include<stdio.h>
#include<sys/shm.h>
#include<stdlib.h>

#define MAX 20
#define BUFFER 1024

struct Process_Data
{
char Process_Name[MAX];
char * Addr;
int Sem_ID;
int Prc_ID;
int Shm_ID;
int BUFFER_SIZE;
};

struct Data_Mesg
{
int No_Of_Processes;
struct Process_Data *Mesg;
};

struct Data_Mesg Data=(struct Data_Mesg*) malloc(sizeof(struct Data_Mesg));

void Shm_Init(void)
{
struct Process_Data *P_Data,*Buf_Data;

int fd_N,fd_PES;
int n;

int shmid,key=1234;
int i=0,k=0;

char ch;
char *shm;

if((fd_N=open("/nparams/pr.txt",0666))==-1)
perror("N file open");

ch=getc(fd_N);
n=atoi(ch);

if((shmid=shmget(key,BUFFER,IPC_CREAT|0666))<0)
perror("Shared Memory get ");

shm=shmat(shmid,(char *) 0 ,0);

if((fd_PES=open("/nparams/PS.txt",0666))==-1)
perror("PES File open");

P_Data=(struct Process_Data *) malloc(n*sizeof(struct Process_Data));
Buf_Data=P_Data;

while(ch=(getc(fd_PES))!=EOF)
{
i=0;k=0;

while(ch!='\n')
{
Buf_Data->Process_Name[i++]=ch;
ch=getc(fd_PES);
}

Buf_Data->Addr=shm;
Buf_Data->Prc_ID=k++;
Buf_Data->BUFFER_SIZE=BUFFER;
Buf_Data->Shm_ID=shmid;
Buf_Data++;
}

Data.No_Of_Processes=n;
Data.Mesg=P_Data;

}

int main()
{
int i=0;
Shm_Init();
printf("\nThe no. of processes are %d\n",Data.No_Of_Processes);
printf("\nProcesses Name ProcessId \n");
while(i<Data.No_Of_Processes)
printf("%s %d\n",Data.Mesg->Process_Name,Data.Mesg->Prc_ID);
}

there are a lot of errors like
incompatible type conversion, illegal initialization , pointer required on the left side... etc etc,,,,,,
i have tried everythin but in vain.....
plz help me out......

[jsmith]

Why don't you format the code using the # button to the right and post the compile errors.

For one thing, this line of code is not inside any function:

struct Data_Mesg Data=(struct Data_Mesg*) malloc(sizeof(struct Data_Mesg));

and Data is not even declared to be a pointer.

[suhassr]

yes thanx man........
i got to knw that........
but why does

FILE * fd_N,*fd_PES;

//files are opened.........

while(!feof(fd_PES)) <- segmentation fault
{
k=0;
*str='\0';
while(!feof(fd_PES)) <- segmentation fault
*str++=fgetc(fd_PES);
.
.
.
.
.
..
.
.
give me segmentation fault ....??
i would really appreciate any help right now........

[jsmith]

According to the above code, you are calling open() and storing the result in a FILE*. open() returns int; fopen() returns FILE*.

But since the above code clearly does not compile, I don't know what code you are actually running that is causing a segmentation fault.

[suhassr]

ya actually i typecast it with (FILE *)open()
i have also tried fopen()
both compiles......
only that dreaded segmentation fault.............

[jsmith]

Ok, simple rule to follow.

If you find that the compiler complains about something unless you typecast it, it almost always means the typecast is wrong.

Your typecast is wrong; if you want to use FILE*/feof, then you need to use fopen().