Re: Mark ItemPointer parameters as const in tuple/table lock functions

On 28.08.25 04:27, Chao Li wrote:
>> On Aug 27, 2025, at 17:24, Peter Eisentraut <peter(at)eisentraut(dot)org> wrote:
>>
>> This style of having Foo be a type alias for pointer-to-FooData is an
>> ancient Postgres coding convention that does not map well to modern C
>> that has an emphasis on judicious use of qualifiers and attributes,
>> and so if this abstraction gets in the way, we sometimes crack it
>> open, like in the case of ItemPointerGetBlockNumber() etc.
>
> You are right, we want to protect the stuff that “tid” points to instead
> of “tid” itself:
>
>      *tid = something; // should hit compile error
>      tid = something; // ok
>
> Also, thanks for telling the history. I have updated the patch to use
> “const ItemPointerData *” in the same way as ItemPointerGetBlockNumber().
>
> Attached is the v2 patch.

This patch still causes a compiler warning:

../src/backend/storage/lmgr/lmgr.c: In function 'XactLockTableWait':
../src/backend/storage/lmgr/lmgr.c:681:27: error: assignment discards
'const' qualifier from pointer target type [-Werror=discarded-qualifiers]

I have fixed that and committed your patch.