Re: [PATCH] Portable flexible arrays instead of r12255

Thanks a lot for your explanation!

Shen, Yu-Teh

On Thu, Oct 18, 2012 at 1:58 PM, Alex Rousskov
<rousskov_at_measurement-factory.com> wrote:
> On 10/17/2012 10:01 PM, Yu-Teh Shen wrote:
>
>> The class FlexibleArray will not delete the *items array, would it cause
>> memory leak?
>
> The class is using placement-new operator to initialize the array.
> Placement-new does not allocate memory. Since the class does not
> allocate memory for the array, it should not delete memory used by the
> array. The caller is responsible for doing both.
>
>
>> And what the shared memory coming from if you don't have copy
>> constructor or something else.
>
> IIRC, the [shared] memory for the array (and the object that includes
> the array as a member) is allocated by various Owner::New() calls in
> ipc/mem/Pointer.h when various shared structures such as StoreMap or
> disker queues are created.
>
> This is complicated, ugly code (but it is the best we could come up
> with). We needed code to allocate and refcount shared memory segments,
> code to initialize the allocated memory, and code to use shared memory
> (in other processes or at other times) without initialization by using
> type casts (with some safety checks).
>
>
> HTH,
>
> Alex.
>
>
>> On Tue, Oct 16, 2012 at 3:56 AM, Alex Rousskov wrote:
>>
>> Hello,
>>
>> Trunk r12255 made Clang compiler happy by removing flexible nonPod[]
>> arrays. Unfortunately, it also moved shared memory items into local
>> memory (in some cases uninitialized). See the "[PATCH] Improve CLANG
>> support" thread.
>>
>> The attached patch provides a Clang-friendly flexible array replacement
>> while keeping items in the shared memory (and using placement-new
>> initialization). The code may have become even less readable, but
>> hopefully more portable.
>>
>> The changes passed build farm tests (except a couple of nodes with
>> Jenkins-related build problems unrelated to the code).
>>
>>
>> Thank you,
>>
>> Alex.
>>
>>
>
Received on Thu Oct 18 2012 - 06:04:57 MDT