How exceptions are handled in C? (return check, exit to OS in fatal error, NULL check, setjmp-longjmp)

Exception handling is C language is done by checking variables or output/return values of the functions. Standard non-void C function returns status code as integer. Zero value indicates a success. Non-zero value indicates failure and the value represents the error code.

Exception handling using return value:
In this example Connect_server() connects the client to the server over a given network.
Syntax:
int connect_server(void);
Return:
zero indicates success.
Non-zero indicates error and return value is the error code.

Exception handling Code:

int error_code = 0;
error_code = connect_server();
if(error_code != 0)
{
  printf("error establishing connection to the server!!\n");
  printf("Error code %d", error_code);
  exit(error_code);
}
else
{
  /*add next steps here*/
}

Returning exception to the operating system:
main() function is also a good example in this context.
main() returns a zero(0) to the operating system to inform that process has been successfully terminated.
main() returns a non-zero value when any exception has occurred.

Code:

int main(int argc, char *argv[])
{
  int error_code = 0;
  error_code = connect_server();
  if(error_code != 0)
  {
    printf("error establishing connection to the server!!\n");
    printf("Error code %d", error_code);
    return error_code;/*error code to OS*/
  }
  else
  {
    /*add next steps here*/
    return 0;/*success code to OS*/
  }
}

Checking NULL pointer:
Another checking that may be performed with pointer variable is NULL checking. Pointers are valid when the value is NULL. If any function returns a valid pointer it should not be NULL. If NULL is returned, then there must be some dynamic memory allocation problem.

Example:

char *name = NULL;
name = (char *)malloc(10);
if(name == NULL)
{
  printf("Not enough memory to run this application");
  exit(-1);
}

setjmp-longjmp:
C language provides a mechanism of setjmp-longjmp to achieve a try-catch style exception handling. Please visit next page to get the details on this topic.

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