Eroare de compilare: user.c: In function ‘dfs_iter’: user.c:44:12: warning: implicit declaration of function ‘stack_new’ [-Wimplicit-function-declaration] struct ra_stack *stack = stack_new(N, sizeof(int)); ^ user.c:44:30: warning: initialization makes pointer from integer without a cast [enabled by default] struct ra_stack *stack = stack_new(N, sizeof(int)); ^ user.c:45:5: warning: implicit declaration of function ‘stack_push’ [-Wimplicit-function-declaration] stack_push(stack, &node); ^ user.c:47:5: warning: implicit declaration of function ‘stack_is_empty’ [-Wimplicit-function-declaration] while (!stack_is_empty(stack)) { ^ user.c:49:9: warning: implicit declaration of function ‘stack_pop’ [-Wimplicit-function-declaration] stack_pop(stack, &ver); ^ user.c: In function ‘main’: user.c:65:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("dfs.in", "r", stdin); ^ user.c:66:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("dfs.out", "w", stdout); ^ user.c:69:10: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &N, &M); ^ user.c:76:14: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &x, &y); ^ /tmp/cc5kkCkd.o: In function `dfs_iter': user.c:(.text+0xef): undefined reference to `stack_new' user.c:(.text+0x101): undefined reference to `stack_push' user.c:(.text+0x10c): undefined reference to `stack_is_empty' user.c:(.text+0x11c): undefined reference to `stack_pop' user.c:(.text+0x148): undefined reference to `stack_push' user.c:(.text+0x157): undefined reference to `stack_is_empty' collect2: error: ld returned 1 exit status