Re: [Boost-users] [test] Malloc exceptions when using test framework on 64bit OS X 10.6.1

Subject: Re: [Boost-users] [test] Malloc exceptions when using test framework on 64bit OS X 10.6.1
From: Peter Klotz (peter.klotz_at_[hidden])
Date: 2009-09-29 00:49:25

Gennadiy Rozental wrote:
> Gennadiy Rozental wrote:
>> Rush Manbert <rush <at> manbert.com> writes:
>>
>>> Now I have gone back and read the original thread about valgrind  
>>> complaints. I see that Gennadiy is rather adamant about not changing  
>>> the code. 
>>
>> I am not adamant. I just want to understand what is wrong and need 
>> some time to look deeper. I plan to look into this Friday/Saturday.
>>
>> Genandiy
>>
>> P.S. Does anyone have vmware image for the system where I can easily 
>> reproduce this?
> 
> Ok. I was able to get hold of freebsd 64 bit image and reproduce this.
> 
> Further investigation uncovered that the issue with statement:
> 
> delete (test_case*)tu.second;
> 
> is not the non-virtual destructor of class test_unit, but the fact that 
> compiler decides to evaluate the expression tu.second twice: once before 
> calling the destructor and once before calling free. By the type the 
> destructor is called tu is invalid.
> 
> Not sure what is so specific about 64 bit, but i believe the issues 
> should be resolved (by caching the value before delete statement).

Hello Gennadiy

Great that you finally had the time to investigate this issue.

I have two remarks about your analysis:

1) Why are you insisting on casting tu.second to test_case*?

Actually you want your derived class destroyed but tu.second is a base 
class pointer of type test_unit*. You can simply call "delete tu.second" 
if the test_unit destructor is virtual. The whole casting thing is in my 
opinion just a workaround for not making the destructor virtual.

2) I am seeing the problem on 32Bit Intel Linux as well, so it is not 
restricted to 64Bit.

Regards, Peter.