I'm using gdb in RedHat to debug C++ code. To better debug my code, I added printf("XXX").
However, after the execution of printf("XXX"), the gdb console didn't show XXX.
Other parts of my code works fine.
1 Answer
It's likely that your output is line-buffered, and because you didn't end the print with a newline, the output hasn't been flushed. Three easy fixes:
std::printf("XXX"); std::fflush(stdout);std::printf("XXX\n");std::puts("XXX");
Also, take care if you're mixing C-style FILE* i/o with C++-style streams.
3 Comments
Rick
I am curious about why this isn't the same case for Windows? I mean, under Windows, debug with Visual Studio, I get output every time with
cout << "hello";, no extra std::endl or std::flush needed. Is it because Visual Studio already taking care of this?
Toby Speight
@Rick, probably the library there is using a different buffering strategy. It's not a platform I've had any contact with, so that would be pure speculation on my part. Perhaps worth asking a question, if it's not already addressed by one?
Rick
Thank you for replying. I don't wanna bother others by asking this question,after all, it's kinda a useless question. I just feel a bit surprised when I don't find any GDB tutorial mentioning this. I mean, this is very important when debugging. For exmaple, I come from Windows, have no idea what's wrong when I don't see the
cout output at first time.
printf("XXX\n");