[Interest] qt and Windows tolerance heap

maitai maitai at virtual-winds.org
Wed Sep 8 09:43:20 CEST 2021

To close the subject:

To force your application to be moved to FTH shim, just create 3 times a 
crash within an hour with

QString *heap = new QString();
delete heap;
delete heap;

then to detect your app has been moved to FTH do

QSettings winsettings( 
QStringList fths = winsettings.childKeys();
foreach(const QString &fth, fths) {
        if(fth == qApp->applicationFilePath()) {
             /* do something*/

Thanks again for your replies and help

-- Philippe

Le 07-09-2021 20:05, maitai a écrit :

> OK, thanks. I will not attempt to modify the registry. I just want to 
> know if that is the case and eventually display a warning.
> The key for that is 
> Now I want to test my changes, I have already forced more than 100 
> crashes in the hope Windows will move me to FTH, no luck :)
> --Philippe
> Le 07-09-2021 17:17, Scott Bloom a écrit :
> You shouldn't need it for a read of the registry, however it is 
> possible that the IT dept of the user, or the user themselves has 
> escalated the default privileges required to read from HKLM
> You might want to code your check to allow for a security violation, so 
> the is it enabled would be yes, no, or "I cant tell" response.
> Scott
> From: Interest <interest-bounces at qt-project.org> On Behalf Of maitai
> Sent: Tuesday, September 7, 2021 7:36 AM
> To: Interest at qt-project.org
> Subject: Re: [Interest] qt and Windows tolerance heap
> Thank you very much that is the way. Do you know if elevated privileges 
> are needed to do that?
> --Philippe
> Le 07-09-2021 15:22, Jérôme Godbout a écrit :
> You can put your aplicaiton into the exclude list, sorry though it was 
> mentionned into the microowft page, but here is the registry key:
> HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\FTH\ExclusionList\myapp.exe
> Change myapp.exe for your actual application.
> From: Jérôme Godbout <jgodbout at dimonoff.com>
> Date: Tuesday, September 7, 2021 at 9:07 AM
> To: maitai <maitai at virtual-winds.org>, Interest at qt-project.org 
> <Interest at qt-project.org>
> Subject: Re: [Interest] qt and Windows tolerance heap
> The tolerant heap only make workaround for actual bug. Disable the 
> tolerant heap for your developers (this should be a system options when 
> developer mode is enabled directly into Windows but sadly you have to 
> do it manually). This will show where your bug is and will appear on 
> dev workstation before they appear on the clients.
> The "myth" of try to launch it again on windows is not really a myth, 
> it come from this feature, the OS try to fix the heap allocation, but 
> the application is still broken. You can also disable your application 
> from using it during the installer.
> To disable:
> https://docs.microsoft.com/en-us/windows/win32/win7appqual/fault-tolerant-heap?redirectedfrom=MSDN
> From: Interest <interest-bounces at qt-project.org> on behalf of maitai 
> <maitai at virtual-winds.org>
> Date: Tuesday, September 7, 2021 at 5:32 AM
> To: Interest at qt-project.org <Interest at qt-project.org>
> Subject: [Interest] qt and Windows tolerance heap
> Hi,
> I have some users (mainly beta testers) that are suffering from 
> "Windows Tolerant Heap" 
> (https://docs.microsoft.com/en-us/windows/win32/win7appqual/fault-tolerant-heap). 
> The consequence of this being activated after some crashes is that the 
> application becomes very slow, plus some mysterious crashes occur 
> randomly deep inside qt event queue manager.
> I know how to remove the app from Tolerant Heap with an elevated 
> command prompt.
> My question is: is there a way from inside the application to detect 
> the app is running in this mode, so I can prompt the user to contact us 
> for instance?
> Thanks for any insight
> Philippe Lelong

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