Initialization from incompatible pointer warning

Question

I have a warning but i can't understand why:

void stampaCon(){
pthread_mutex_lock(&mutexCon);

  printf("lista dei connesi: \n");
  int i;
    for(i=0; i<=MAX_CONNECTIONS*8; i++){
        if(arrayCon[i]!=NULL){
            TipoListaReg *s = NULL;

            s = arrayCon[i]; //gives me a warning

            printf("utente %s\n", arrayCon[i]->utente);
            while(s->next!=NULL){
                printf("utente %s\n", s->next->utente);
                s=s->next;
            }
        }
    }

    pthread_mutex_unlock(&mutexCon);

}

TipoListaReg structure is:

typedef struct NodoListaReg { 
  char utente[MAX_NAME_LENGTH+1];
  int connesso; 
  ListaPendente *msgs;
  struct NodoListaReg *next;
} TipoListaReg;

and arrayReg is a global variable defined as:

TipoListaReg *arrayReg[512];

and this is a struct ListaPendente:

typedef struct pendenti{ 

  char msg[MAX_MSG_SIZE];
  char mittente[MAX_NAME_LENGTH+1];
  int type;
  struct pendenti *next;
}ListaPendente;

the warning is:

warning: assignment from incompatible pointer type [-Wincompatible-pointer-types]

Pleas post a [MCVE](https://stackoverflow.com/help/mcve) because this is not enough information to help you. — Iharob Al Asimi, Aug 30 '17 at 15:27
@yano on some keyboards (Italian, for example) that's not where the backtick is. Actually on some keyboards (again, Italian) there's no backtick at all. — Federico klez Culloca, Aug 30 '17 at 15:31
Are you by chance trying to initialize the variable in global scope? That won't work, try it in main function. Refer to this post: https://stackoverflow.com/questions/3025050/error-initializer-element-is-not-constant-when-trying-to-initialize-variable-w — savram, Aug 30 '17 at 15:34

Jabberwocky · Answer 1 · 2017-08-30T15:42:21.493

There is not really enough information in your question, but this compiles fine without warnings:

typedef struct ListaPendente  // made up definition by me as you didn't provide
{                             // the definition of ListaPendente 
  int dummy;
} ListaPendente ;

typedef struct NodoListaReg {
  char utente[100];           // MAX_NAME_LENGTH replaced by 100 as it is not relevant
  int connesso;
  ListaPendente *msgs;
  struct NodoListaReg *next;
} TipoListaReg;

TipoListaReg *arrayReg[512];

int main()
{
  int i = 0;
  TipoListaReg *s = arrayReg[i];    // no warning here
}

However the code won't do anything useful

Initialization from incompatible pointer warning

1 Answers1