Compilare: main.c: In function 'make_pair': main.c:10:14: warning: implicit declaration of function 'strdup'; did you mean 'strcmp'? [-Wimplicit-function-declaration] 10 | x->first=strdup(a); | ^~~~~~ | strcmp main.c:10:13: warning: assignment to 'char *' from 'int' makes pointer from integer without a cast [-Wint-conversion] 10 | x->first=strdup(a); | ^ main.c: In function 'poptotree': main.c:144:29: warning: pointer 'nod' used after 'free' [-Wuse-after-free] 144 | free(nod->val); | ~~~^~~~~ main.c:143:21: note: call to 'free' here 143 | free(nod); | ^~~~~~~~~