Compilare: main.cpp: In function 'int gcd(int, int)': main.cpp:8:13: warning: unused variable 'r' [-Wunused-variable] int r = b; ^ main.cpp:6:9: warning: unused variable 'r' [-Wunused-variable] int r = 0; ^ main.cpp: In function 'int main()': main.cpp:21:20: warning: right operand of comma operator has no effect [-Wunused-value] cin >> a, b; ^ main.cpp:16:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("euclid2.in", "r", stdin); ^ main.cpp:17:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("euclid2.out", "w", stdout); ^ main.cpp:9:11: warning: 'b' may be used uninitialized in this function [-Wmaybe-uninitialized] b = a % b; ~~^~~~~~~ main.cpp:15:5: note: 'b' was declared here int main() { ^~~~