Обсуждение: Fix incorrect const qualification for tbm_add_tuples() and itemptr_to_uint64()
Hi Hackers,
I noticed a wrong const qualification:
```
void
tbm_add_tuples(TIDBitmap *tbm, const ItemPointer tids, int ntids,
bool recheck)
tbm_add_tuples(TIDBitmap *tbm, const ItemPointer tids, int ntids,
bool recheck)
```
This "const" only protects "tids" itself from updating, which is meaningless. I believe the real intention should be protecting the content "tids" pointing to from updating.
This behavior can be easily proved by the compiler. If we add a line of fake code in the function:
```
tids[0].ip_posid = 0;
```
With current "const ItemPointer tids", the compiler won't report any problem. If we change to "const ItemPointerData *tids", the compiler will raise an error due to the assignment to read-only variable.
I searched over the source tree, and found only one more occurrence in itemptr_to_uint64(), so I fixed it as well.
Also, as I am touching tbm_add_tuples(), I did a tiny change that moved the loop variable "i" into "for". Peter Eisentraut just did the same change in formatting.c [1].
[1] https://git.postgresql.org/cgit/postgresql.git/commit/?id=03fbb0814c5015ab79e670ab97bb6a3349269e4b
Best regards,
Chao Li (Evan)
---------------------
HighGo Software Co., Ltd.
https://www.highgo.com/
https://www.highgo.com/
Вложения
Re: Fix incorrect const qualification for tbm_add_tuples() and itemptr_to_uint64()
От
Peter Eisentraut
Дата:
On 29.10.25 04:11, Chao Li wrote: > I noticed a wrong const qualification: > ``` > void > tbm_add_tuples(TIDBitmap *tbm, const ItemPointer tids, int ntids, > bool recheck) > ``` > > This "const" only protects "tids" itself from updating, which is > meaningless. I believe the real intention should be protecting the > content "tids" pointing to from updating. > > This behavior can be easily proved by the compiler. If we add a line of > fake code in the function: > ``` > tids[0].ip_posid = 0; > ``` > > With current "const ItemPointer tids", the compiler won't report any > problem. If we change to "const ItemPointerData *tids", the compiler > will raise an error due to the assignment to read-only variable. > > I searched over the source tree, and found only one more occurrence in > itemptr_to_uint64(), so I fixed it as well. I have committed this, and I also found a few more similarly confused cases across the tree, which I also fixed. > Also, as I am touching tbm_add_tuples(), I did a tiny change that moved > the loop variable "i" into "for". Peter Eisentraut just did the same > change in formatting.c [1]. I don't know, let's leave unrelated changes for a separate patch.