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Fix possible uninitialized variable warning (#4334) 

I got this warning when compiling citus:
```
../columnar/write_state_management.c: In function ‘PendingWritesInUpperTransactions’:
../columnar/write_state_management.c:364:20: warning: ‘entry’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  if (found && entry->writeStateStack != NULL)
               ~~~~~^~~~~~~~~~~~~~~~
```

I fixed this by checking by always initializing entry, by using an early
return if `WriteStateMap` didn't exist. Instead of using the `found`
variable to check for existence of the key, I now simply check the
`entry` variable itself.

To quote the postgres comment on the hash_enter function:

> If foundPtr isn't NULL, then *foundPtr is set true if we found an
> existing entry in the table, false otherwise.  This is needed in the
> HASH_ENTER case, but is redundant with the return value otherwise.
pull/4330/head
Jelte Fennema 2020-11-20 16:02:03 +01:00 committed by GitHub
parent 856e5c85cf
commit b2def22ab1
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 13 additions and 17 deletions
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30
src/backend/columnar/write_state_management.c
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@ -200,17 +200,16 @@ cstore_init_write_state(RelFileNode relfilenode, TupleDesc tupdesc,
void
FlushWriteStateForRelfilenode(Oid relfilenode, SubTransactionId currentSubXid)
{
WriteStateMapEntry *entry = NULL;
bool found = false;
if (WriteStateMap)
if (WriteStateMap == NULL)
{
entry = hash_search(WriteStateMap, &relfilenode, HASH_FIND, &found);
return;
}
Assert(!found || !entry->dropped);
WriteStateMapEntry *entry = hash_search(WriteStateMap, &relfilenode, HASH_FIND, NULL);
if (found && entry->writeStateStack != NULL)
Assert(!entry || !entry->dropped);
if (entry && entry->writeStateStack != NULL)
{
SubXidWriteState *stackEntry = entry->writeStateStack;
if (stackEntry->subXid == currentSubXid)
@ -315,16 +314,14 @@ DiscardWriteStateForAllRels(SubTransactionId currentSubXid, SubTransactionId par
void
MarkRelfilenodeDropped(Oid relfilenode, SubTransactionId currentSubXid)
{
bool found = false;
if (WriteStateMap == NULL)
{
return;
}
WriteStateMapEntry *entry = hash_search(WriteStateMap, &relfilenode, HASH_FIND,
&found);
if (!found || entry->dropped)
NULL);
if (!entry || entry->dropped)
{
return;
}
@ -353,15 +350,14 @@ NonTransactionDropWriteState(Oid relfilenode)
bool
PendingWritesInUpperTransactions(Oid relfilenode, SubTransactionId currentSubXid)
{
WriteStateMapEntry *entry;
bool found = false;
if (WriteStateMap)
if (WriteStateMap == NULL)
{
entry = hash_search(WriteStateMap, &relfilenode, HASH_FIND, &found);
return false;
}
if (found && entry->writeStateStack != NULL)
WriteStateMapEntry *entry = hash_search(WriteStateMap, &relfilenode, HASH_FIND, NULL);
if (entry && entry->writeStateStack != NULL)
{
SubXidWriteState *stackEntry = entry->writeStateStack;