[PATCH] Bury leaked pointers in a global array to silence a leak detector in --disable-free mode

[Chandler Carruth]

On Fri, Dec 27, 2013 at 3:01 AM, Kostya Serebryany <kcc at google.com> wrote:

> On Fri, Dec 27, 2013 at 11:44 AM, Kostya Serebryany <kcc at google.com>wrote:
>
>>
>>
>>
>> On Fri, Dec 27, 2013 at 11:39 AM, Chandler Carruth <chandlerc at gmail.com>wrote:
>>
>>>
>>> On Fri, Dec 27, 2013 at 2:10 AM, Kostya Serebryany <kcc at google.com>wrote:
>>>
>>>> +  // This function may be called only a small fixed amount of times
>>>> per each
>>>> +  // invocation, otherwise we do actually have a leak which we want to
>>>> report.
>>>> +  // If this function is called more than kGraveYardMaxSize times, the
>>>> pointers
>>>> +  // will not be properly buried and a leak detector will report a
>>>> leak, which
>>>> +  // is what we want in such case.
>>>>
>>>
>>> Interesting. I didn't realize it was going to be *that* tightly bounded.
>>>
>>> This makes me wonder if the whole disable free thing should just be
>>> removed at this point.
>>>
>> I am all for it, --disable-free looks like a hack and we did not see any
>> compile-time loss from removing it (measure on bootstrap).
>>
>
> I take these my words back. Building 483.xalancbmk with -O0 (make -j32)
> shows around 0.5%-1% compile-time difference:
> with -disable-free :
> TIME: real: 8.140; user: 177.970; system: 13.180
> TIME: real: 8.070; user: 177.940; system: 13.090
> TIME: real: 8.103; user: 177.960; system: 13.410
> TIME: real: 8.122; user: 178.110; system: 13.180
> TIME: real: 8.093; user: 177.660; system: 13.210
> without -disable-free :
> TIME: real: 8.140; user: 179.750; system: 13.260
> TIME: real: 8.113; user: 178.770; system: 13.710
> TIME: real: 8.101; user: 179.830; system: 13.180
> TIME: real: 8.262; user: 180.160; system: 12.760
> TIME: real: 8.125; user: 179.510; system: 13.070
>
> 0.5% may be worth this relatively innocent hack.
>

Yea, I think we could fix this by making the ASTContext's destructor do
less work ... but whatever, this patch LGTM. =]
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