#include <glog/logging.h>
#include <gflags/gflags.h>

int increment(int* x) {
    (*x)++;

    return 42;
}

int main(int argc, char* argv[]) {
    google::ParseCommandLineFlags(&argc, &argv, true);
    google::InitGoogleLogging(argv[0]);

    int x = 0;

    LOG(INFO) << "Info message";
    LOG(WARNING) << "Warning message, x = " << x;
    LOG_IF(INFO, 42 == increment(&x)) << "Shouldn't be logged: " << increment(&x);
    LOG(WARNING) << "x should be 0, but is: " << x;

    return 0;
}

bash-4.1$ ./log_example --logtostderr
I0909 15:09:53.077044 16647 log_example.cc:16] Info message
W0909 15:09:53.077115 16647 log_example.cc:18] Warning message, x = 0
I0909 15:09:53.077121 16647 log_example.cc:20] Shouldn't be logged: 42
W0909 15:09:53.077124 16647 log_example.cc:22] x should be 0, but is: 2
bash-4.1$ ./log_example --logtostderr --minloglevel=1
W0909 15:09:55.013198 16650 log_example.cc:18] Warning message, x = 0
W0909 15:09:55.013213 16650 log_example.cc:22] x should be 0, but is: 2