passing pointer to function and using realloc - c++

Question

I want to pass a pointer to a function which will call a second function that will use realloc.
The issue is that realloc is returning NULL.
I don't know if the mistake is in the numbers of * in the function call or something else.
Could you please help me ?
The code:
int main(){
// some code.
clause_t* ptr; //clause_t is a structure i declared.
//Some work including the initial allocation of ptr (which is working).
assignLonely(matSAT, ic.nbClause, ic.nbVar, ptr); //the issue is here.
//Some other work
}
void assignLonely(int** matSAT, int nbClause, int nbVar, clause_t* ptr)
{
int i = 0, j = 0;
int cpt = 0;
int indice = -1;
for (i = 0; i < nbClause ; ++i)
{
j = 0;
cpt = 0;
while((j < nbVar) && (cpt < 2))
{
if (matSAT[i][j] != 0)
{
cpt++;
}
else
{
indice = j;
}
if (cpt < 2)
{
deleteClause(indice, &ptr);
}
j++;
}
}
}
void deleteClause(int indiceClause, clause_t** ptr)
{
int i = indiceClause;
int nbElt = sizeof((*ptr))/sizeof((*ptr)[0]);
int tailleElt = sizeof((*ptr)[0]);
while(i+1 < nbElt)
{
(*ptr)[i] = (*ptr)[i+1];
i++;
}
*ptr = (clause_t*)realloc(*ptr, (nbElt-1)*tailleElt);
if (*ptr == NULL)
{
fprintf(stderr, "Erreur reallocation\n");
exit(EXIT_FAILURE);
}
}

Answer 1

You have to declarae function assignLonely similarly to function deleteClause like
void assignLonely(int** matSAT, int nbClause, int nbVar, clause_t** ptr);
if you want that changes of ptr in the function would be stored in the original object in main.
Also take into account that this statement
int nbElt = sizeof((*ptr))/sizeof((*ptr)[0]);
is wrong.
Expression sizeof((*ptr)) will return the size of the pointer. Pointers do not keep information about how many elements in arrays they point to.
So expression
(nbElt-1)
can be equal to zero or even be negative.