How can I see cout output in a non-console application?

Question

It seems rather tedious to output to debug window. Where can I find cout output if I am writing a non-console information ?

Like:

double i = a / b;
cout << b << endl;//I want to check out whether b is zero. It seems the output cannot be found anywhere.

Answer 1

The question is very clear. How use std::cout to debug a non-console application in Visual Studio.

The answer is very clear: you cannot. That is, Visual Studio does not support std::cout as debug tool for non-console applications.

This is a serious limitation of Visual Studio, probably a failure to meet the C++ standard even. I find it very sad to see disinformative "answers" here trying to hide this defect of their precious Visual Studio.

Answer 2

For a Windows solution, you can allocate a console, and bind cout/cin to it. For example:

AllocConsole();
freopen("CONOUT$", "w", stdout);
freopen("CONOUT$", "w", stderr);  

Documentation:
https://msdn.microsoft.com/en-us/library/windows/desktop/ms681944%28v=vs.85%29.aspx

Answer 3

SOLUTION: This answer solves the question and allows you to redirect console output to the Visual Studio Output window. First we need a class that overrides the default cout string stream:

class dbg_stream_for_cout
    : public std::stringbuf
{
public:
    ~dbg_stream_for_cout() { sync(); }
    int sync()
    {
        ::OutputDebugStringA(str().c_str());
        str(std::string()); // Clear the string buffer
        return 0;
    }
};
dbg_stream_for_cout g_DebugStreamFor_cout;

Then, somewhere you want to "activate" writing to the VS output window:

std::cout.rdbuf(&g_DebugStreamFor_cout); // Redirect std::cout to OutputDebugString!

Answer 4

To output a string to the debug console, use OutputDebugStringA. See http://msdn.microsoft.com/en-us/library/windows/desktop/aa363362%28v=vs.85%29.aspx

To output variable values to the debug console, using std::ostringstream, the send the string to OutputDebugStringA.

Excessive output statements will cause the program to severly slow down. However, it is a good technique to catch things the debugger has a problem with, such as the actual child members when playing with base pointers.

Answer 5

I'd like to give my 2 cents.

Given that the maybe is a VS issue about compliancy with the C++ standard or that we could use OutputDebugStringA, if you cannot modify your code base you may like the idea of simply redirect the std::cout to something else, like a file.

So without changing your code base you can do something like suggested here:How to redirect cin and cout to files?

Condensed:

• add the include #include <fstream>
• at the beginning of your app, in some init, before logging you can use:

std::ofstream out("out.txt");
std::streambuf *coutbuf = std::cout.rdbuf(); //save old buf
std::cout.rdbuf(out.rdbuf()); //redirect std::cout to out.txt!

• the at the end of your app/logging:

std::cout.rdbuf(coutbuf); //reset to standard output again

Hope this may help someone, Kudos to Nawaz that provided the answer in the other thread.

Answer 6

Instead of using cout, create a log file and write anything you want into it.

Edit: Use this simple code for writing to a log file.

ofstream log;
log.open ("log.txt");
log << "Writing this to a file.\n";
log.close();

Answer 7

You can use .Net functions such as System::Diagnostics::Debug::WriteLine("your message"). You can even add a condition to print only during the debug mode and not in the release mode. For example:

#ifdef DEBUG   
   System::Diagnostics::Debug::WriteLine("your message");
#endif   

Answer 8

Yes, indeed, it's annoying.

Here's how I do it :

#define DBOUT( s )            \
{                             \
std::wostringstream os_;    \
   os_ << s;                   \
   OutputDebugStringW( os_.str().c_str() );  \
}
// example :    DBOUT("some text " << some_variable << "   some more text" << some_other_varaible << "\n");