[PATCH][Review request] unix.Malloc checker improvement: +handling new/delete, +memory.MismatchedFree, +memory.MismatchedDelete, +improved display names for allocators/deallocators

[Jordan Rose]

On Mar 29, 2013, at 13:50 , Anna Zaks <ganna at apple.com> wrote:

> 
> On Mar 29, 2013, at 11:57 AM, Anton Yartsev <anton.yartsev at gmail.com> wrote:
> 
>> On 29.03.2013 22:04, Anna Zaks wrote:
>>> 
>>> On Mar 28, 2013, at 5:42 PM, Anton Yartsev <anton.yartsev at gmail.com> wrote:
>>> 
>>>>>> Evolved one more problem to solve: if overloaded standard operator new is defined and is called as a function, then it is not recognized as overloaded operator for some reason. Tests testOpNewArray() and testOpNew() in NewDelete-custom.cpp cover these issue.
>>>>> 
>>>>> You can check if it has to do with redeclarations of the allocator function, but I wouldn't expect that. Definitely something we need to fix before putting out another open-source checker build.
>>>> Addressed the issue. Actually the problem is caused by the fact, that overloaded operator new was inlined and has not been processed by checkPostStmt(const CallExpr) at all as it skips inlined calls.
>>>> What Is the reason for skipping inline calls?
>>>> 
>>> 
>>> The idea is that if a function has been inlined, it will be modeled through inlining where we will know exactly what it does. 
>>> 
>>> It is unclear if we should enforce the malloc/free, new/delete rules on inlined functions. For example, in this case, if someone overloaded the operator new, do we want to ensure that delete was called on the object regardless of what new's custom implementation is?
>> It seems to me that if we just simply handle inline functions without analyzing the implementation
> 
> Currently, C.wasInlined() == true means that we did analyze the implementation.
> 
>> it'll give less false-positives then false-negatives if we just skip them as most malloc/new functions are expected to allocate memory. Or I haven't got something?
> 
> The implementation could be more precise in telling you what happened (did the function allocate memory or not).
> You'd get less false negatives if you just do not track regions allocated by inlined functions - less tracking -> less bug reports -> less false positives. No? However, you might miss real bugs(have false negatives).
> 
> Said that, I do not think that the current decision is supported by real world examples, as it should be….

I agree with Anna: for now, we should be conservative and not track things that come out of a custom definition of the global operator new. We can revisit this later, since it's usually the case that they should still be deleted, but for now let's keep this behavior. You can change your test cases to just not include the definition of the global operators, which matches both libc++ and libstdc++.

Sorry for not noticing this sooner, which would have saved you a little runaround.

Jordan

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