[Interest] Memory Leak when instantiating QWidget based windows

[Andy]

Ah - sorry.  I can see how that's unclear (pre-coffee email).

I meant the Debug section on the left-hand side of the main window:
Welcome, Edit, Design, Debug,...

Then the bottom pane pops up below the editor and has a dropdown at the
top-left - Debugger, Clang Static Analyzer, Memcheck,...

---
Andy Maloney  //  https://asmaloney.com
twitter ~ @asmaloney <https://twitter.com/asmaloney>


On Thu, Sep 8, 2016 at 9:13 AM, Edward Sutton <edward.sutton at subsite.com>
wrote:

> Hi Andy,
>
> Could you please elaborate on step #3?
>
> I cannot find a Memcheck option under Preferences > Debugger.
>
> Thanks for the tips!
>
> -Ed
> Qt Creator 4.01 with Qt 5.6.1
>
>
> On Sep 8, 2016, at 7:56 AM, Andy <asmaloney at gmail.com> wrote:
>
> Mike:
>
> If you haven't already tried it, using Qt Creator in combination with
> valgrind works really well to track these kinds of things down.
>
> The basics:
>
>   1) install valgrind (I used homebrew)
>   2) point Qt Creator at it in the prefs (Analyzer->Valgrind)
>   3) Click the Debug tab, set the tool to Memcheck, and click the start
> button (little green arrow)
>
> After it runs your application (slowly), it will spit out a bunch of info
> about memory leaks that make it pretty easy to track down the problems.
>
>
>
>
> ---
> Andy Maloney  //  https://asmaloney.com
> <https://urldefense.proofpoint.com/v2/url?u=https-3A__asmaloney.com&d=DQMFaQ&c=G4BpsyPyB19LB50bn2swXw&r=cAG2c-SQES5P2qb8IW-uwnBOCX_f2qYJIlzenFnoHUc&m=c5VUb3aKymRQx0ih8A7yljotGOJbYdQ2iJ1PDgaS508&s=r8u8ZRFO-Qd4fneoIZohXBUjpcA_h7vjbk3y92UEclg&e=>
> twitter ~ @asmaloney
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>
> On Thu, Sep 8, 2016 at 6:55 AM, Konstantin Shegunov <kshegunov at gmail.com>
> wrote:
>
>>
>> On Wed, Sep 7, 2016 at 11:23 PM, Mike Jackson <imikejackson at gmail.com>
>> wrote:
>>
>>> We monitor the memory use before and after the loop using OS X's
>>> Activity monitor. At the end of the loop there is more memory being used
>>> than before the loop, by about 2~3MB worth.
>>>
>>
>> This isn't reliable. Consider the following C++ only code:
>>
>> int main(int argc, char ** argv)
>>
>> {
>>
>>     struct X;
>>
>>     X * x = nullptr;
>>
>>
>>     struct X {
>>
>>         int data[1024];
>>
>>     };
>>
>>
>>     for (qint32 i = 0; i < 100000; i++)  {
>>
>>         x = new X[1024];
>>
>>         delete x;
>>
>>     }
>>
>>     return 0;
>>
>> }
>>
>>
>> In the KSysGuard (KDE's system monitor) I observe for the memory consumption: 12 908k, 23 048k shared before the loop and 12 944k, 25 112k shared after the loop. There isn't a leak here, yet there's a difference. The OS's heap manager may free the memory immediately, may cache it, or hold on to it. Ultimately it's out of your control, that's why you should use a code analyzer (like valgrind to track leaks).
>>
>>
>> Kind regards.
>>
>>
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