如何在Windows上的控制台输出上中断（设置断点）？

Question

Background:

I'm running a large nUnit test suite on my developer PC (via nunit-console) and I'm seeing some garbage output in the console window.

The units under test do involve .NET code as well as underlying C++ and C libraries and I haven't yet found out who is producing the garbage output.

Question:

Is there a single Windows API function where all Console output goes through? (regardless where it comes from.)

I have tried setting a breakpoint inside WriteConsole but that doesn't even catch printf output from the CRT. Is there any "central" location to set a breakpoint to catch all console output in a Windows application? (Some Nt... function?)

Answer 1

Console I/O makes calls to ReadFile and WriteFile on Windows. WriteFile is the routine for console output. It would be best to hook or breakpoint WriteFile and filter the handle specified to it. Don't mistake actual File I/O for operations on a console handle.

To acquire the correct handle used for console output on a Windows process:

GetStdHandle(STD_OUTPUT_HANDLE);

Alternatively, opening the console output handle using CreateFile and specifying CONOUT$ works and is also recommended:

HANDLE console_output = CreateFileA("CONOUT$", GENERIC_WRITE, FILE_SHARE_WRITE, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);

This will return the handle you need to watch for in WriteFile calls. Just like with a hook though, you can specify the conditions for your breakpoint and check for the correct console handle in the call.

There is more about operations on console handles using ReadFile/WriteFile in the Microsoft documentation