Re: [eigen] Alignment of a derived class

[Martin Sälzle <martin.saelzle@xxxxxxx>]

Hi Gael,

Thank you very much for your clear answer.

best regards
Martin

Am 18.07.2012 um 17:29 schrieb Gael Guennebaud:

> Hi Martin,
> 
> On Wed, Jul 18, 2012 at 4:18 AM, Martin Sälzle <martin.saelzle@xxxxxxx> wrote:
>> Hi,
>> 
>> Please consider this example:
>> 
>> struct Base
>> {
>>  Eigen::Vector4f vec4f_base;
>>  EIGEN_MAKE_ALIGNED_OPERATOR_NEW
>> };
>> 
>> struct Derived1 : public Base
>> {
>>  Eigen::Vector4f vec4f_derived_1;
>>  EIGEN_MAKE_ALIGNED_OPERATOR_NEW
>> };
>> 
>> struct Derived2 : public Base
>> {
>>  Eigen::Vector4f vec4f_derived_2;
>> };
>> 
>> I would like to know if Derived1 and / or Derived 2 are aligned, given that Base is aligned.
> 
> yes for both.
> 
>> The next question is if EIGEN_MAKE_ALIGNED_OPERATOR_NEW is needed in the derived class (Derived1 vs Derived2).
> 
> No, having it in Base is enough.
> 
>> The final question is what would happen for Derived1 if Base does note have EIGEN_MAKE_ALIGNED_OPERATOR_NEW?
> 
> On a 64bits system nothing special. On a 32bits system with SSE
> enabled, an abort or segfault if you create a Derived1 on the heap
> using "new Derived1".
> 
> gael
> 
>> thank you and best regards,
>> Martin
>> 
> 
>