Re: [eigen] strange sizeof on windows

["Benoit Jacob" <jacob.benoit.1@xxxxxxxxx>]

2009/1/5 FMDSPAM <fmdspam@xxxxxxxxx>:
>> can you try this:
>>
>> struct empty {};
>> struct foo : empty
>> {
>>  float x;
>> };
>>
>> and print sizeof(foo), sizeof(empty), sizeof(float) ?
>>
>
> Sure,
>
> sizeof(foo) = 4
> sizeof(empty) = 1
> sizeof(float) = 4

Thanks very much. So at least here, your compiler has performed the
EBCO (empty base class optimization)
http://www.informit.com/articles/article.aspx?p=31473&seqNum=2
(Indeed that turns out to be a nonstandard optimization performed only
by certain compilers).

The question now is, why doesn't it perform the EBCO with Eigen::Matrix ?
Maybe it's related to the multiple inheritance. Can you please try:

struct empty1 {};
struct empty2 {};
struct foo : empty1, empty2
{
 float x;
};

what is sizeof(foo) now ?

Cheers,
Benoit

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