Re: Use C11 alignas instead of palloc/malloc for alignment

On 16.09.26 11:16, Peter Eisentraut wrote:
> On 08.09.26 12:08, Peter Eisentraut wrote:
>> There are a number of places where palloc()/malloc()/etc. was used
>> solely to obtain an aligned buffer.  We can do these much simpler by
>> using alignas with a local variable instead.  See attached patch.
>
> Here is a new patch set that aims to address all the comments.

Here is a rebased patch set. No functional changes over v3.

>
> First of all, while changing this to make use of the existing
> "AlignedBlock" types, I noticed that PGAlignedXLogBlock is misnamed: It
> should be PGIOAlignedXLogBlock, to maintain the similarity with
> PGAlignedBlock and PGIOAlignedBlock, respectively.  So I'm proposing to
> rename it in patch 0001.
>
> We could then re-introduce the "correct" PGAlignedXLogBlock and make use
> of it, which is patch 0003. But I'm hesitant to change the meaning of
> PGAlignedXLogBlock without some gap in between, so I'm not sure about
> this patch.
>
> Patch 0002 is as before, but with the "AlignedBlock" types used, and the
> copy_file() change backed out and a comment added.
>
> Patch 0004 adds some comments and an assertion for HEADER_SCRATCH_SIZE,
> and patch 0005 refactors things to convert the workspace from static
> variable to a normal (non-static) local variable.  (This could be
> squashed into 0002, but it seems cleaner to review this way at least.)
>
> (The pgindent changes were already committed separately.)