Assertions are slow when running on Windows with a debugger attached

[pgroke]

Description

Assertions are slow when running on Windows with a debugger attached.

The reason is the unconditional call of OutputDebugStringA which takes a comparatively very long time when a debugger is attached.

In my case the difference in execution time was dramatic. E.g. one test took over a minute when started from the IDE (with the debugger attached), while it takes less than a second when running without a debugger (same Debug build).

Also, in Visual Studio, the frequent calls of OutputDebugStringA with an empty string seem to overflow some buffer every now and then - Visual Studio periodically prints *** Output truncated by debugger *** in the debug window.

When I added a check so that OutputDebugStringA is only called when there's actually something to print, the execution time went down to about the time when running without a debugger (< 1 second in my case) -- and the *** Output truncated by debugger *** messages are gone too.

I've prepared a pull request.

Steps to reproduce

• Write a simple test that does a lot of assertions (100k+) in otherwise trivial & fast code.
• Compile for Windows with Visual Studio, Debug configuration
• Start outside of Visual Studio without any debugger attached
• Start from inside Visual Studio with debugger attached

Extra information

• doctest version: v2.4.3
• Operating System: Windows 10 x64 1909
• Compiler+version: Visual Studio 2019 16.8.6
• Configuration: x64-Debug

[pgroke]

The windows-2016-gcc and windows-2019-gcc tests fail because the package http://repo.msys2.org/mingw/x86_64/mingw-w64-x86_64-expat-2.2.9-1-any.pkg.tar.xz is no longer available. Unfortunately I have no idea where those tests are defined, so I also don't know how (where) to fix it.

[onqtam]

I'm closing this as it has already been fixed (again thanks for reporting) - will release an official version soon!

[pgroke]

Sure! Thanks for the library :)