Compilare: user.c: In function ‘_disjoint_set_forest_new’: user.c:52:5: warning: implicit declaration of function ‘malloc’ [-Wimplicit-function-declaration] _disjoint_set_forest* forest = (_disjoint_set_forest*)malloc(sizeof(_disjoint_set_forest)); ^ user.c:52:59: warning: incompatible implicit declaration of built-in function ‘malloc’ [enabled by default] _disjoint_set_forest* forest = (_disjoint_set_forest*)malloc(sizeof(_disjoint_set_forest)); ^ user.c:53:22: warning: assignment from incompatible pointer type [enabled by default] forest -> forest = (int*)malloc(size * sizeof(_disjoint_set_forest_node)); ^