Re: Don't cast away const where possible - Mailing list pgsql-hackers

From Peter Eisentraut
Subject Re: Don't cast away const where possible
Date
Msg-id 65a5d629-4cbe-4530-9ab7-b0d06bd5e0b6@eisentraut.org
Whole thread Raw
In response to Re: Don't cast away const where possible  (Bertrand Drouvot <bertranddrouvot.pg@gmail.com>)
Responses Re: Don't cast away const where possible
List pgsql-hackers
On 29.12.25 10:01, Bertrand Drouvot wrote:
> On Mon, Dec 22, 2025 at 12:53:03PM +0100, Peter Eisentraut wrote:
>> On 18.12.25 14:55, Bertrand Drouvot wrote:
>>> Some functions are casting away the const qualifiers from their signatures in
>>> local variables.
>>
>> @@ -1304,8 +1304,8 @@ merge_overlapping_ranges(FmgrInfo *cmp, Oid colloid,
>>   static int
>>   compare_distances(const void *a, const void *b)
>>   {
>> -       DistanceValue *da = (DistanceValue *) a;
>> -       DistanceValue *db = (DistanceValue *) b;
>> +       const DistanceValue *da = (const DistanceValue *) a;
>> +       const DistanceValue *db = (const DistanceValue *) b;
>>
>> I wonder if the better fix here wouldn't be to get rid of the cast. It's not
>> necessary, and without it the compiler would automatically warn about
>> qualifier mismatches.
> 
> Yeah, that looks better as it provides an extra safety check should the function
> signature change.
> 
>> These comparison functions seem to be a common
>> pattern.
> 
> Right, in the attached I applied your proposal on all those places.

I have committed patch 0003 (pg_saslprep).

For patch 0002, I don't understand the change for getRootTableInfo(). 
It returns tbinfo->parents[0] (possibly some levels deep), but the 
parents field is not const-qualfied, so I don't understand the claim 
that this fixes anything.

For patch 0001, this seems good, but I wonder why your patch catches 
some cases and not some other similar ones.  For example, in 
src/backend/access/brin/brin_minmax_multi.c, you change 
compare_distances(), but not the very similar compare_expanded_ranges() 
and compare_values() nearby.




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