[Interest] Crash in Qt OpenSSL thread

Roland Hughes roland at logikalsolutions.com
Tue Mar 23 12:28:15 CET 2021


I am assuming that running the application under Valgrind at the client 
site to catch the crash is not an option.

Suggestions in order of least amount of pain. Since I see .dll in your 
output I will also assume Windows platform.

1.) Run CppCheck and other static source analysis tools to make certain 
you don't have an uninitialized member variable. If you are open to 
purchasing a commercial one, Gimpel's PC-lint used to be one of the best 
on the market back when I still did development on the evil OS.

2.) Run your application under Valgrind like the user has been and check 
for memory leaks.

"Rare crash" failing on an allocation usually means "slow leak" and a 
long-run application. Eventually you exceed the memory allowed the user 
account or in the entire machine. Bounds Checker used to be really great 
for this and it didn't bury the application like Valgrind does.

https://en.wikipedia.org/wiki/BoundsChecker

3.) I don't think they have added it to QSysInfo (or any other) class 
yet, a platform independent way of getting current free memory in some 
unit. I've had to add this to many embedded systems. If your application 
already has logging then this is the cats meow.

a.) add a configurable timer.

b.) add lastFreeSize and initial to zero

c.) write a slot that is the target of the timer. Every N minutes grab 
the amount of free RAM. If it is different by y% write an entry to the 
log. Don't be tempted to write it each and every time as you can chew up 
quite a bit of disk if the application starts and runs forever.

When your application already has some kind of logging you can get some 
idea if the problem is either your code or something else on the 
computer. It's possible they tried to open a 5 million row spreadsheet 
or something like that. Pesky Windows users, always opening a hundred 
funny cat videos.

The timer slot thing is kind of nice because you can set some minimum 
threshold and pop up a warning message to the user that their computer 
is low on memory and ask them to close half of those funny cat videos.

On 3/23/21 6:00 AM, interest-request at qt-project.org wrote:
> We use Qt 5.12.10. It seems it's a rare crash. Any thoughts what can be
> the cause of it and can it be fixed somehow?

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Logikal Solutions
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