Re: [Boost-users] [Chrono] Memory leak in Chrono?

Subject: Re: [Boost-users] [Chrono] Memory leak in Chrono?
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2013-02-13 13:11:46

Le 13/02/13 14:30, Don a écrit :
>> Subject: Re: [Boost-users] [Chrono] Memory leak in Chrono?
>> From: "Vicente J. Botet Escriba" <vicente.botet_at_[hidden]>
>> Date: 2/12/2013 1:17 PM
>>
>> Le 12/02/13 18:13, gast128 a écrit :
>>> we use Boost.Chrono too. MFC applications incorrectly report memory 
>>> leaks, which can easily be solved.
>> Hi,
>>
>> if you have some patches to propose to avoids this incorrect reports 
>> I would try to include them.
>
> Vincente,
>
> I am using MFC, but I don't believe this is a MFC false-leak report.
>
> I added a destructor for duration_units_default_initializer_t, like 
> this (near the end of chrono/io/duration_units.hpp):
>
>         ~duration_units__t()
>           {
>             if (duration_units_default_holder<CharT>::initialized_)
>             {
>               delete[] 
> duration_units_default_holder<CharT>::n_d_valid_units_;
> duration_units_default_holder<CharT>::n_d_valid_units_ = 0;
>               delete[] 
> duration_units_default_holder<CharT>::valid_units_;
> duration_units_default_holder<CharT>::valid_units_ = 0;
> duration_units_default_holder<CharT>::initialized_ = false;
>             }
>           }
>
> This solves the memory leak, and seems to work fine for my simple test 
> program. 
I could add this is this helps on the MFC report.
> But n_d_valid_units_, valid_units_, and initialized_ are static 
> variables, so I assume you want to only create these variables once.
Right.
>
> When run with my test program and step through it in the debugger, 
> only one instantiation of duration_units_default_initializer_t occurs. 
> (That is, once for each char type, single-byte and wide.) 
This is the goal of the type (implement a singleton). This technique is 
used in some Boost libraries already

> This occurs when the duration_units_default_initializer is 
> instantiated (at the very end of duration_units.hpp). Since this is a 
> global variable, this occurs during application startup and the 
> destructor runs during application shuttdown. 
Right, this was the reason the destructor didn't do anything.
> But presumably this can occur in some other situations, otherwise why 
> would you have all the logic of making valid_units_ etc. class-static 
> variables. 

On which other situation do you think this could occur?

Best,
Vicente
> I don't think I understand enough about what is going on to propose a 
> robust solution.
>