[sqlite] Using uninitialized value nDummy when calling vdbePmaReaderInit

[Rowan Worth]

On 15 August 2015 at 14:35, Carlos Tangerino 
wrote:
>
> The variable nDummy is not initialized *(1)* in the function but its
> pointer *(2)* is passed to *vdbePmaReaderInit* that increments *(3)* its
> value.
>

nDummy is never used after vdbePmaReaderInit though, so it doesn't really
matter that its value is undefined, right?
-Rowan

[sqlite] Using uninitialized value nDummy when calling vdbePmaReaderInit

[Carlos Tangerino]

Bug list return me error, so posting here hoping someone watchs it.
A suspicious piece of code.

The variable nDummy is not initialized *(1)* in the function but its
pointer *(2)* is passed to *vdbePmaReaderInit* that increments *(3)* its
value.

static int vdbeMergeEngineLevel0(
  SortSubtask *pTask, /* Sorter task to read from */
  int nPMA,   /* Number of PMAs to read */
  i64 *piOffset,  /* IN/OUT: Readr offset in pTask->file */
  MergeEngine **ppOut /* OUT: New merge-engine */
){
  MergeEngine *pNew;  /* Merge engine to return */
  i64 iOff = *piOffset;
  int i;
  int rc = SQLITE_OK;

  *ppOut = pNew = vdbeMergeEngineNew(nPMA);
  if( pNew==0 ) rc = SQLITE_NOMEM;

  for(i=0; iaReadr[i];
rc = vdbePmaReaderInit(pTask, >file, iOff, pReadr, &*nDummy*);
*-(2)*
iOff = pReadr->iEof;
  }

  if( rc!=SQLITE_OK ){
vdbeMergeEngineFree(pNew);
*ppOut = 0;
  }
  *piOffset = iOff;
  return rc;
}


static int vdbePmaReaderInit(
  SortSubtask *pTask, /* Task context */
  SorterFile *pFile,  /* Sorter file to read from */
  i64 iStart, /* Start offset in pFile */
  PmaReader *pReadr,  /* PmaReader to populate */
  i64 **pnByte* /* IN/OUT: Increment this value by PMA
size */
){
  int rc;

  assert( pFile->iEof>iStart );
  assert( pReadr->aAlloc==0 && pReadr->nAlloc==0 );
  assert( pReadr->aBuffer==0 );
  assert( pReadr->aMap==0 );

  rc = vdbePmaReaderSeek(pTask, pReadr, pFile, iStart);
  if( rc==SQLITE_OK ){
u64 nByte;/* Size of PMA in bytes */
rc = vdbePmaReadVarint(pReadr, );
pReadr->iEof = pReadr->iReadOff + nByte;
**pnByte* += nByte;
*--(3)*
  }

  if( rc==SQLITE_OK ){
rc = vdbePmaReaderNext(pReadr);
  }
  return rc;
}

Regards