[PATCH] [ASan] Make BlockingMutex really linker initialized.

[Yuri Gribov]

On Fri, Feb 20, 2015 at 5:19 AM, Alexey Samsonov <vonosmas at gmail.com> wrote:
>
> On Wed, Feb 18, 2015 at 5:29 AM, Yury Gribov <y.gribov at samsung.com> wrote:
>>
>> On 02/06/2015 09:10 AM, Yury Gribov wrote:
>>>
>>> On 02/04/2015 07:23 PM, David Blaikie wrote:
>>>>
>>>> On Wed, Feb 4, 2015 at 3:56 AM, Yury Gribov <tetra2005 at gmail.com> wrote:
>>>>
>>>>>> Yes, I think enabling -Wglobal-constructors for ASan (and for all the
>>>>>
>>>>> rest sanitizers) will be great.
>>>>>
>>>>>
>>>>> FYI it was relatively easy to get this working on Linux (with ~500
>>>>> lines
>>>>> of changes). Unfortunately Windows compiler lacks too many necessary
>>>>> features: explicit initialization of array members, constexpr,
>>>>> unrestricted
>>>>> unions (all still missing in VS2013 and we still use VS2012). Having
>>>>> #if
>>>>> WINDOWS all over the place isn't an option as well so I'm afraid we
>>>>> are out
>>>>> of luck.
>>>>>
>>>>
>>>> Perhaps there's a relatively small number of structures (probably
>>>> templates) we could create to keep all of this logic (and Windows
>>>> workarounds/suppressions) in one place so it could scale to all the use
>>>> cases we have?
>>>
>>>
>>> Thanks for the idea, I'll check this next week.
>>
>>
>> Folks,
>>
>> Here is a draft version (not full-blown patch but rather a PoC). The main
>> part is in sanitizer_internal_defs.h (classes LinkerInitializedArray and
>> LinkerInitializedStructArray). I also slightly changed atomic types in
>> sanitizer_atomic.h (volatile members can't be linker-initialized). Does this
>> look sane in general?
>
> +Timur for Windows parts.
> Overall, yes, although missing constexpr is such a pain (sigh). Why is it
> necessary to initialize all fields to 0 in LinkerInitialized constructor?

You mean some classes may want non-zero values there? That's true, I
planned to address this (the patch is a draft anyway).

>> I've did full rebuild and regtests on Linux (compiler-rt built by trunk
>> Clang, GCC 4.8 and Clang 3.1). I haven't done full testing on Windows and
>> Mac but at least relevant parts of sanitizer_internal_defs.h compiled fine.
>>
>> If all this makes sense, how should I proceed with a refactoring of this
>> scale? Is it mandatory to verify _all_ platforms or I could to some extent
>> rely on respected maintainers to fix errors? The former would be quite a
>> burden.
>
> Well, at least for LLVM, we have buildbots (for Linux/Mac/Windows), so it's
> fine to test your change on available platforms, and then watch the
> buildbots closely.

Ok.

> It would be awesome to rollout this out gradually, first by introducing
> LinkerInitializedArray, then converting global objects to use constexpr
> constructor one by one, and enabling -Wglobal-constructor as a final change.

Right.

-Y