[BUG] Console created through AllocConsole does not receive colored output

[bstordrup]

Describe the bug
I use benchmark.dll inside a non-console application because I want to benchmark different implementations of ways to solve the same problem. And it is not possible to extract the code into a separate project, as the benchmarked code calls several other functions.

Therefore, I rolled my own BenchmarkMain method that does the same as BENCHMARK_MAIN macro, but also creates a console with AllocConsole, creates std::ostream instances for STD_OUTPUT_HANDLE and STD_ERROR_HANDLE, creates a ConsoleReporter instance and calls RunSpecificBenchmarks with this displayReporter.

The console did receive output, but it reported that Color printing was only supported on Windows - which makes no sense as the console being written to is on Windows.

Along the way, the std::cout.rdbuf() is saved, and replaced with the the same .rdbuf() that is used for the std::ostream out instance.

System

• OS: Windows 11 23H2 (build 22631.2861)
• Compiler and version: Visual C++ 2022 (Visual Studio 2022 17.8.3), cl.exe version 19.38.33133 for x64

To reproduce
Inside a non-console application, add the following function:

int BenchmarkMain (int argc, char **argv)
{
    char arg0_default[] = "benchmark";
    char* args_default = arg0_default;
    if (!argv) {
      argc = 1;
      argv = &args_default;
    }

    if (!argv)
    {
        argc = 2;
        argv = (char **) args_default;
    }

    ::benchmark::Initialize (&argc, argv);
    if (::benchmark::ReportUnrecognizedArguments (argc, argv))
    {
        return 1;
    }

    // Create console reporter
    AllocConsole ();
    HANDLE stdOutHandle = GetStdHandle (STD_OUTPUT_HANDLE);
    HANDLE stdErrHandle = GetStdHandle (STD_ERROR_HANDLE);


    // Get file descriptors
    int fdOut = _open_osfhandle ((intptr_t) stdOutHandle, _O_TEXT);
    int fdErr = _open_osfhandle ((intptr_t) stdErrHandle, _O_TEXT);

    // Get FILE*
    FILE *fpOut = _fdopen (fdOut, "w");
    FILE *fpErr = _fdopen (fdErr, "w");

    // Create ofstream
    std::ofstream outStream (fpOut);
    std::ofstream errStream (fpErr);

    // Create ostream
    std::ostream out (outStream.rdbuf ());
    std::ostream err (errStream.rdbuf ());

    auto savedBuf = std::cout.rdbuf ();
    std::cout.rdbuf (outStream.rdbuf ());

    auto displayReporter = std::make_unique<::benchmark::ConsoleReporter> ();
    displayReporter->SetOutputStream (&out);
    displayReporter->SetErrorStream (&err);

    ::benchmark::RunSpecifiedBenchmarks (displayReporter.get());

    // Restore std::cout.rdbuf() - otherwise an exception is thrown at exit.
    std::cout.rdbuf (savedBuf);

    return 0;
}

Make sure that the function is being called when the application starts - I control this with a command line parameter.

Note that the output written to the console is without any color formatting.

Expected behavior
Output from benchmarking should get color-enabled output in the created console window

Additional context
The application, where I call the benchmark library, is a MFC Windows application created with use of an external library (CodeJock).

[dmah42]

can you point to where the bug in the library is that is causing the issue, as opposed to an issue with how you're redirecting the various streaming buffers?

[bstordrup]

Updated the issue to more precisely describe the problem.

There are two places in code that contributes to this error:

1. In console_reporter.cc, there is a check on the output stream where std::cout is directly compared to GetOutputStream(), and if different, the "Color printing is only supported..." is reported.
2. The ColorPrintf (std::ostream& out, LogColor color, const char* fmt, va_list args) method operates directly on stdout for flushing the stream and uses vprintf to make the actual output.

I have a branch in my local fork with changes in these two places that makes color printing work in a Console window created with AllocConsole.

[dmah42]

ah great, thank you for the clarification! :)