Compilare: user.c: In function ‘main’: user.c:16:1: warning: implicit declaration of function ‘malloc’ [-Wimplicit-function-declaration] number = malloc(length * sizeof(char) + 1); ^ user.c:16:10: warning: incompatible implicit declaration of built-in function ‘malloc’ [enabled by default] number = malloc(length * sizeof(char) + 1); ^ user.c:46:1: warning: implicit declaration of function ‘free’ [-Wimplicit-function-declaration] free(number); ^ user.c:46:1: warning: incompatible implicit declaration of built-in function ‘free’ [enabled by default] user.c:15:7: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(file1, "%d", &length); ^ user.c:19:7: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(file1, "%s", number); ^