Char** problem

[PrinceDamon]

I am programming a TP with c , and I have this function that bugs and I do not know how to fix it; I have been trying for the last five days, and I still can't find where the problem is;so please help me fix it.

char **EtatsAccess(Automate *automate)
{
    char **TabEtatAccess= malloc(sizeof(**TabEtatAccess));
                int nbEtatAccess=0;int i=0;//i c'est l'element en cours
                TabEtatAccess[nbEtatAccess]=automate->EtatInit;
                //char *chaine=automate->EtatInit;
                nbEtatAccess++;
                        if (automate->tab_transition == NULL)
                            {
                                exit(EXIT_FAILURE);
                            }
                            while(i<nbEtatAccess)
                            {
                              Instruction *actuel = automate->tab_transition->premier;
                                while (actuel != NULL)
                                {
                                    if(strcmp(TabEtatAccess[i],actuel->etatInit.nom)==0)
                                    {
                                        //vérifier si cet elem n'existe pas
                                        BOOLEAN exist=0;
                                        int i1=0;
                                        for(i1=0;i1<nbEtatAccess;i1++)
                                        {
                                            if (strcmp(TabEtatAccess[i1],actuel->etatFin.nom)==0)
                                            {
                                                exist=1;
                                                break;
                                            }
                                        }
                                        //Ajouter cet element
                                        if(!exist)
                                        {
                                         TabEtatAccess[nbEtatAccess]=actuel->etatFin.nom;
                                         actuel->etatFin.esAccess=1;
                                         nbEtatAccess++;
                                        }
                                    }
                                    actuel = actuel->suivant;
                                }
                                i++;
                            }


                            AffichEtatAccess(TabEtatAccess,nbEtatAccess);
                            automate->nbEtatAccess=nbEtatAccess;
                            return TabEtatAccess;
}

[stahta01]

I suggest posting enough code so it can be compiled.
I am think the info about the type Automate is at least needed.
Edit: Info on type Instruction will likely also be needed.


You do know that you are NOT likely allocating enough size in the malloc call?
Note: This is just a guess since your code is NOT really clear on what you are trying to allocate to me.

Tim S.

[Salem]

Well first of all, learning how to indent code properly would significantly aid in clarity (both for you and us).

char **EtatsAccess(Automate * automate)
{
  char **TabEtatAccess = malloc(sizeof(**TabEtatAccess));
  int nbEtatAccess = 0;
  int i = 0;                    //i c'est l'element en cours
  TabEtatAccess[nbEtatAccess] = automate->EtatInit;
  //char *chaine=automate->EtatInit;
  nbEtatAccess++;
  if (automate->tab_transition == NULL) {
    exit(EXIT_FAILURE);
  }
  while (i < nbEtatAccess) {
    Instruction *actuel = automate->tab_transition->premier;
    while (actuel != NULL) {
      if (strcmp(TabEtatAccess[i], actuel->etatInit.nom) == 0) {
        //vérifier si cet elem n'existe pas
        BOOLEAN exist = 0;
        int i1 = 0;
        for (i1 = 0; i1 < nbEtatAccess; i1++) {
          if (strcmp(TabEtatAccess[i1], actuel->etatFin.nom) == 0) {
            exist = 1;
            break;
          }
        }
        //Ajouter cet element
        if (!exist) {
          TabEtatAccess[nbEtatAccess] = actuel->etatFin.nom;
          actuel->etatFin.esAccess = 1;
          nbEtatAccess++;
        }
      }
      actuel = actuel->suivant;
    }
    i++;
  }


  AffichEtatAccess(TabEtatAccess, nbEtatAccess);
  automate->nbEtatAccess = nbEtatAccess;
  return TabEtatAccess;
}

Next, you need to learn how to use malloc properly.
> char **TabEtatAccess = malloc(sizeof(**TabEtatAccess));
Every * in the declaration needs it's own independent malloc call. You can't allocate a ** variable in a single malloc call.

So for example,

char **TabEtatAccess;
TabEtatAccess = malloc( numberOfRows * sizeof(*TabEtatAccess) );
for ( i = 0 ; i < numberOfRows ; i++ )
    TabEtatAccess[i] = malloc( numberOfCols * sizeof(*TabEtatAccess[i]) );

// This is the malloc equivalent of
// char TabEtatAccess[numberOfRows][numberOfCols]

Also notice the use of sizeof in this code. Using the form p = malloc( sizeof(*p) ); saves you from having to check back at the declaration to get the type right.

> TabEtatAccess[nbEtatAccess] = actuel->etatFin.nom;
You might want to think hard about what you're doing here.
It looks like you're going to end up with two pointers in two different data structures pointing at the SAME bit of memory.
If one of those data structures is deallocated, the other could end up with garbage pointers.

For safety, you should really make a copy of the string using strcpy() - remembering to make sure you have enough memory allocated.

[PrinceDamon]

Hi, thank you so much for taking time and helping me with my tp, and Im sorry for posting my code that way, but now I learned how to indent code correctely thanks to your advice.
Besides, you explained well how to use malloc, so I corrected all the memory allocations in my TP, and now everything works, thank you again.

char **EtatsAccess(Automate *automate)
{
    char **TabEtatAccess;
    TabEtatAccess= malloc(20*sizeof(*TabEtatAccess));
    int nbEtatAccess=0;int i=0;               //i c'est l'element en cours
    ///**Initialisation**///
    TabEtatAccess[nbEtatAccess]=malloc(10*sizeof(*TabEtatAccess[nbEtatAccess]));
    strcpy(TabEtatAccess[nbEtatAccess],automate->EtatInit);
    nbEtatAccess++;
    if (automate->tab_transition == NULL){
     exit(EXIT_FAILURE);
    }
    while(i<nbEtatAccess){
        Instruction *actuel = automate->tab_transition->premier;
        while (actuel != NULL){
            if(strcmp(TabEtatAccess[i],actuel->etatInit.nom)==0){
               //vérifier si cet elem n'existe pas
                BOOLEAN exist=0;
                int i1=0;
                for(i1=0;i1<nbEtatAccess;i1++)
                {
                    if (strcmp(TabEtatAccess[i1],actuel->etatFin.nom)==0){
                        exist=1;
                        break;
                    }
                }
                //Ajouter cet element
                if(!exist){
                    TabEtatAccess[nbEtatAccess]=malloc(10*sizeof(*TabEtatAccess[nbEtatAccess]));
                    strcpy(TabEtatAccess[nbEtatAccess],actuel->etatFin.nom);
                    actuel->etatFin.esAccess=1;
                    nbEtatAccess++;
                }
            }
        actuel = actuel->suivant;
        }
    i++;
    }
    AffichEtatAccess(TabEtatAccess,nbEtatAccess);
    automate->nbEtatAccess=nbEtatAccess;
    return TabEtatAccess;
}