Accessing struct variables in a function pthread - c

Question

What is the proper way to access the struct variables in a function that is called by pthread_creation. This is how I am trying to do
void *add_first_quat(void *a){
struct thread1Struct *myArray = (struct thread1Struct *)a;
int i ;
for(i= *myArray>start; i < *myArray>end; i++){
sum+= *myArray>th1Array[i];
}
/* the function must return something - NULL will do */
return NULL;
}
And in my struct I am defining two variables and pointer to a globally defined array
struct thread1Struct{
int start = 0;
int end = 25;
int *th1Array = myArray;
};
This is how I am calling pthread_create function
(pthread_create(&inc_first_quater_thread, NULL, add_first_quat, (void*) &th1StrObj))
Why my code is not working? I am getting following errors
main.c: In function ‘add_first_quat’:
main.c:14:9: error: dereferencing pointer to incomplete type
for(i= *myArray>start; i < *myArray>end; i++){
^
main.c:14:18: error: ‘start’ undeclared (first use in this function)
for(i= *myArray>start; i < *myArray>end; i++){
^
main.c:14:18: note: each undeclared identifier is reported only once for each function it appears in
main.c:14:29: error: dereferencing pointer to incomplete type
for(i= *myArray>start; i < *myArray>end; i++){
^
main.c:14:38: error: ‘end’ undeclared (first use in this function)
for(i= *myArray>start; i < *myArray>end; i++){
^
main.c:15:9: error: dereferencing pointer to incomplete type
sum+= *myArray>th1Array[i];
^
main.c:15:18: error: ‘th1Array’ undeclared (first use in this function)
sum+= *myArray>th1Array[i];
^
main.c: At top level:
main.c:34:12: error: expected ‘:’, ‘,’, ‘;’, ‘}’ or ‘__attribute__’ before ‘=’ token
int start = 0;
^

Answer 1

First problem (syntax):
Try myArray->start or (*myArray).start or myArray[0].start. The first syntax would be my preference in this case.
Second problem:
dereferencing pointer to incomplete type
You need to provide the full declaration before referencing any fields.
Solve the problem by moving the full declaration of the struct to the top of your code file, or put it in a .h file that you #include in all source files that use the struct.

Answer 2

This: *myArray>start is not the proper syntax for accessing members of a pointer to a struct.
You could do this: (*myArray).start, which dereferences the pointer so *myArray is of type struct thread1Struct, then use . for member access.
The preferred way is myArray->start, where the -> operator does member access for a pointer to struct.

Answer 3

The problem lies in the way you're accessing the elements of the structure. Your expression *myArray>start makes no sense to the compiler. As you know, myArray is a pointer to a struct. You can access the data members in two ways :
You could use the indirection operator (eg. (*myArray).start )
You could use the arrow operator (eg. myArray->start)
This is how you access data members of any struct pointer. It does not pertain p-threads alone.