Cannot get STD handle to AllocConsole

Question

I've been trying to get the output handle to my console, but it doesn't seem to work. I got it to set the color of my text, but it's not changing.

HANDLE hOut = GetStdHandle(STD_OUTPUT_HANDLE);
SetConsoleTextAttribute(hOut, 0x0A)

I tried to debug it and I think I the handle isn't right. Is there any other way to do this, and is it normal that it doesn't work? Any fixes?

Thanks!

EDIT: Let me clarify, the handle that I'm trying to get is invalid. I've no idea how to fix it. I guess I'll start looking for alternatives; maybe something is wrong with my code.

someone else had commented and it was in response to that comment which was subsequently removed by the author. — Graeme Wicksted
– Graeme Wicksted, Commented Aug 23, 2017 at 15:29

Ben Voigt · Accepted Answer · 2017-08-24 19:18:09Z

5

The standard handlers are initialized during process creation, if you call AllocConsole the new console is created far later. AllocConsole can change the standard handles, but it's far too late for them to be used by startup code, such as the C runtime library initialization.

The best thing to do in this case is CreateFileW(L"CONOUT$", ...), which gets a console handle no matter whether you are attached to parent process's console, the OS created one for you because your PE header is /SUBSYSTEM:CONSOLE, or you called AllocConsole. And it gets the console handle even when standard handles are redirected.

And if you think you may call FreeConsole, you should be sure to close any handles returned by CreateFile first. In the general case where the console remains active until process exit, you can let the OS close the handle for you during process cleanup.

edited Aug 24, 2017 at 19:18

answered Aug 22, 2017 at 17:04

Ben Voigt

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2 Comments

Ben Voigt Over a year ago

@AxIoN: freopen_s acts on a FILE*, it doesn't give you a HANDLE that you need to pass to SetConsoleTextAttribute. My answer is not how to fix GetStdHandle, but rather how to get a console handle 100% reliably.

Ben Voigt Over a year ago

@eryksun: Is this documented officially, or just observed behavior which might be version specific? Ahh, I see it here in GetStdHandle

Graeme Wicksted · Accepted Answer · 2017-08-23 15:27:16Z

1

Since you specify hOut is INVALID_HANDLE_VALUE (or potentially NULL), try calling GetLastError to find out why. It is likely you don't have console session established.

Is this a win32 Console Application or is it a Windows SubSystem application (does it have WinMain?)

You could try AttachConsole(ATTACH_PARENT_PROCESS) instead of AllocConsole before GetStdHandle.

In either case, AllocConsole and AttachConsole return a BOOL which, if FALSE, indicates you can call GetLastError to find out why.

Make sure you aren't calling hOut = GetStdHandle(STD_OUTPUT_HANDLE) followed by CloseHandle(hOut) prior to the lines listed above. Unlike AllocConsole and FreeConsole, closing the std handle is not a good idea.

Finally, try:

#define _WIN32_WINNT 0x0501 before #include <windows.h>

edited Aug 23, 2017 at 15:27

answered Aug 22, 2017 at 16:47

Graeme Wicksted

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1 Comment

SoLux Over a year ago

It has a different name but I wanted to change it into just out when posting and I had a typo (twice). And I did mention that the handle was invalid, though I've no idea how to fix it

Mecanik · Accepted Answer · 2019-10-30 09:34:40Z

0

So much drama for such a small thing... and by the way @Ben's answer is the proper answer is actually right.

For your problem, just do this:

freopen("CONIN$", "r", stdin);
freopen("CONOUT$", "w", stdout);
freopen("CONOUT$", "w", stderr);

This will allow you to get the handle of any console you have. Make sure you put this after AllocConsole();

Enjoy?!

edited Oct 30, 2019 at 9:34

answered Nov 26, 2017 at 7:40

Mecanik

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1 Comment

Haydn V. Harach Over a year ago

I was having a similar issue and this solved it. I put this code after AllocConsole but before GetStdHandle.

SoLux · Accepted Answer · 2017-08-22 18:55:02Z

-1

Ok so I found an answer. Seems like a simple edit can fix it

#define setcsattr(clr) SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE), clr)

answered Aug 22, 2017 at 18:55

SoLux

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6 Comments

Eryk Sun Over a year ago

This is the same code as in the question -- just in a macro and without an intermediate HANDLE variable.

SoLux Over a year ago

Yes, it seems that that was the problem.

Eryk Sun Over a year ago

What was the problem? I don't see any practical difference.

SoLux Over a year ago

The initialization of the handle was not right. my fix was just a fast fix

Eryk Sun Over a year ago

If the handle value itself is bad, this macro doesn't do anything to fix it. This makes no sense as an answer. But I didn't downvote it.

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