Re: gratuitous casting away const - Mailing list pgsql-hackers

From Mark Dilger
Subject Re: gratuitous casting away const
Date
Msg-id 96DBB26C-34FF-4090-98A8-6DDA5136AC73@gmail.com
Whole thread Raw
In response to Re: gratuitous casting away const  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: gratuitous casting away const  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
> On Sep 20, 2016, at 1:06 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> Mark Dilger <hornschnorter@gmail.com> writes:
>> Would patches to not cast away const be considered?
>
> In general, yes, but I'm not especially in favor of something like this:
>
>> bool
>> PageIndexTupleOverwrite(Page page, OffsetNumber offnum,
>> -                                               Item newtup, Size newsize)
>> +                                               const char *newtup, Size newsize)
>> {
>
> since that seems to be discarding type information in order to add
> "const"; does not seem like a net benefit from here.

The following seems somewhere in between, with ItemPointer
changing to const ItemPointerData *.  I expect you would not care
for this change, but thought I'd check to see where you draw the line:


diff --git a/src/backend/access/gin/ginbulk.c b/src/backend/access/gin/ginbulk.c
index 71c64e4..903b01f 100644
--- a/src/backend/access/gin/ginbulk.c
+++ b/src/backend/access/gin/ginbulk.c
@@ -244,7 +244,7 @@ ginInsertBAEntries(BuildAccumulator *accum,static intqsortCompareItemPointers(const void *a, const
void*b){ 
-   int         res = ginCompareItemPointers((ItemPointer) a, (ItemPointer) b);
+   int         res = ginCompareItemPointers((const ItemPointerData *) a, (const ItemPointerData *) b);
   /* Assert that there are no equal item pointers being sorted */   Assert(res != 0);
diff --git a/src/include/access/gin_private.h b/src/include/access/gin_private.h
index bf589ab..2e5a7dff 100644
--- a/src/include/access/gin_private.h
+++ b/src/include/access/gin_private.h
@@ -968,7 +968,7 @@ extern ItemPointer ginMergeItemPointers(ItemPointerData *a, uint32 na, * so we want this to be
inlined.*/static inline int 
-ginCompareItemPointers(ItemPointer a, ItemPointer b)
+ginCompareItemPointers(const ItemPointerData *a, const ItemPointerData *b){   uint64      ia = (uint64)
a->ip_blkid.bi_hi<< 32 | (uint64) a->ip_blkid.bi_lo << 16 | a->ip_posid;   uint64      ib = (uint64) b->ip_blkid.bi_hi
<<32 | (uint64) b->ip_blkid.bi_lo << 16 | b->ip_posid; 





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