Compilare: user.cpp: In function ‘int main()’: user.cpp:53:10: warning: unused variable ‘flag’ [-Wunused-variable] bool flag = 0; ^ user.cpp:54:54: warning: unused variable ‘a1’ [-Wunused-variable] double a, b, c, d1, d2, c1, c2, l, w, ans, area, a1, b1, x1, y1, x2, y2; ^ user.cpp:54:58: warning: unused variable ‘b1’ [-Wunused-variable] double a, b, c, d1, d2, c1, c2, l, w, ans, area, a1, b1, x1, y1, x2, y2; ^ user.cpp:56:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("rubarba.in", "r", stdin); ^ user.cpp:57:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("rubarba.out", "w", stdout); ^ user.cpp:59:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d", &n); ^ user.cpp:62:45: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%lf%lf", &P [i].x, &P [i].y); ^ user.cpp:88:27: warning: ‘y2’ may be used uninitialized in this function [-Wmaybe-uninitialized] ans = (x2 - x1) * (y2 - y1); ^ user.cpp:88:15: warning: ‘x2’ may be used uninitialized in this function [-Wmaybe-uninitialized] ans = (x2 - x1) * (y2 - y1); ^ user.cpp:88:27: warning: ‘y1’ may be used uninitialized in this function [-Wmaybe-uninitialized] ans = (x2 - x1) * (y2 - y1); ^ user.cpp:88:15: warning: ‘x1’ may be used uninitialized in this function [-Wmaybe-uninitialized] ans = (x2 - x1) * (y2 - y1); ^