Question

typedef struct _ut_slot {
   ucontext_t uc;
   ....
}*ut_slot;

static ut_slot*  table;  //array of the structs

void foo (int tab_size){
     table =  malloc ( tab_size *(sizeof (ut_slot))); // memory allocation for array of structs 
     for(i = 0 ; i < tab_size ; i++  ){
        getcontext(&table[i].uc); <--- ?????? 
      }
}

I receive error in “getcontext” string. How can I write reference to any element of the array? And how can I initialize with “getcontext” command the “uc” field of each array element?

Answer 1

You have an inconsistency with the definition of ut_slot and the use of it:

typedef struct _ut_slot {
   ucontext_t uc;
   ....
}*ut_slot; //<--- pointer to struct

You say that ut_slot is a pointer to a struct, then you declare

static ut_slot* table;

so you have a pointer-to-pointer-to-struct.

You probably want ut_slot to just be a struct, or table to be a pointer-to-struct.

---

To be more precise: table is a pointer-to-pointer-to-struct, so table[i] is a pointer-to-struct, and you try to access a struct member of a non-struct with table[i].ut, which raises a compilation error.

---

Try the following:

typedef struct _ut_slot {
   ucontext_t uc;
   ....
} ut_slot; //removed "*"

static ut_slot *table;

the rest of your code is okay and doesn’t need to be changed.