Question

Here is the code

#include<stdio.h>
#include<sys/types.h>
#include<stdlib.h>
#include<pthread.h>
typedef struct std_thread
{
 char name[20];
 int hallno;
 int empid;
 char dept[5];
}std[5];

void *print(void *args)
{
 struct std_thread *data=(struct std_thread *)args;
 printf("My thread id is %ld\n",pthread_self());
 printf("Thread %d is executing\n",args);
 printf("Name\tHall No\tEmployee ID\tDepartment\n");
 printf("--------------------------------------------------------");
 printf("%s\t%d\t%d\t%s\n",data->name,data->hallno,data->empid,data->dept);
}

int main()
{
 pthread_t th[5];
 int empid=2020;
 int hall=1;
 char dept[2]="IT";
 char *names[]={"dinesh","vignesh","pradeep","prasath","mohan"};
 int t;
 int i;
 int status;
 for(i=0;i<5;i++)
 {
   std[i].name=names[i]; //Getting error from this line
   std[i].hallno=hall;   //Error at this line
   hall++;
   std[i].empid=empid;  //Error at this line
   empid++;
   std[i].dept=dept;     //Error at this line
   status=pthread_create(&th[i],NULL,print,(void *)&std[i]);
   if(status)
   {
    printf("Error creating threads\n");
    exit(0);
   }

 }
 pthread_exit(NULL);
}

While compiling this code, I’m getting “syntax error before ‘[‘ token”. What is the reason for this?

Answer 1

This declaration does not do what you think it does:

typedef struct std_thread
{
  ...
}std[5];

This declares a struct named std_thread, and then it creates a typedef named std to mean “an array of 5 struct std_thread objects”.

You probably wanted one of these two definitions, in order to declare a global object named std as an array of 5 struct std_thread‘s:

typedef struct std_thread
{
  ...
} std_thread;
std_thread std[5];

// OR

struct std_thread
{
  ..
} std[5];

In the first case, we also create the typedef named std_thread as an alias for struct std_thread; in the second case, we do not.

Furthermore, as others have stated, you cannot copy character arrays by assignment. You must copy them using a function such as strcpy(3) or strncpy(3). When using strcpy, you must ensure that the destination buffer is large enough to hold the desired string. Also keep in mind that strncpy does not necessarily null-terminate its destination string, so use it with caution.