[cfe-dev] [RFC] Linux bots should set MALLOC_PERTURB_

[Alexander Potapenko]

Does the attached testcase belong to the LLVM test suite? If it does
not, have you tried to run asanified Clang on that?

On Tue, Jul 22, 2014 at 3:01 PM, İsmail Dönmez <ismail at donmez.ws> wrote:
>
>
>
> On Tue, Jul 22, 2014 at 2:00 PM, İsmail Dönmez <ismail at donmez.ws> wrote:
>>
>> Hi,
>>
>>
>> On Tue, Jul 22, 2014 at 1:58 PM, Alexander Potapenko <glider at google.com>
>> wrote:
>>>
>>> IIUC this flag does not make glibc invalidate the _pointers_ to freed
>>> memory, it just overwrites the contents of the freed memory with
>>> garbage.
>>> Picking different flag values results in different garbage values,
>>> which may affect the behavior of buggy programs and thus help detect
>>> the presence of a read-after-free (not a write-after-free or
>>> double-free - the latter is handled by MALLOC_CHECK_).
>>> This flag can't be used together with ASan, because ASan replaces the
>>> libc allocator with its own one. ASan's use-after-free/double-free
>>> detection is far more reliable.
>>
>>
>> Thanks for your reply! I know Asan and MALLOC_PERTURB_ is now compatible
>> but they uncover similar bugs with latter being really lightweight and
>> less-capable. But still as in PR20228 it uncovers bugs which Asan didn't
>> find (I guess?).
>>
>
>
> s/now/not
>
> of course...
>
>



-- 
Alexander Potapenko
Software Engineer
Google Moscow