Alignment test is unreliable on linux due to unaligned access fixups in kernel

[ccollins]

On ia64, alpha and a number of other archs, the Linux kernel installs a unaligned access fixup handler which hides unaligned accesses from userspace tasks. There is still a significant performance hit however.

Attached patch fixes the test under linux by disabling the fixup handler for that test if prctl() is available.

[ccollins]

alignment check fixup patch for linux

[doughera]

Thanks for the patch. Fortunately, it doesn't really matter either way -- the result is only used for two ASSERT checks in unmanagedstruct.pmc, so there's no real performance impact.

It might be easier to just get rid of the whole Configure step.

[jkeenan]

Replying to doughera:

> Thanks for the patch.  Fortunately, it doesn't really matter either way -- 
> the result is only used for two ASSERT checks in unmanagedstruct.pmc, so 
> there's no real performance impact.  
> 
> It might be easier to just get rid of the whole Configure step.

I confirmed tonight what Andy D wrote nine months ago. On that basis, I'm going to reject this patch and close this ticket. However, I'm hoping a new ticket in which we can specifically consider getting rid of auto::alignptrs.

Thank you very much.
kid51