| Re: [eigen] Alignment of a derived class |
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- To: eigen@xxxxxxxxxxxxxxxxxxx
- Subject: Re: [eigen] Alignment of a derived class
- From: Gael Guennebaud <gael.guennebaud@xxxxxxxxx>
- Date: Wed, 18 Jul 2012 23:29:29 +0200
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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
>