SQLite

** results in register target.  The results are guaranteed to appear
** in register target.
*/
int sqlite3ExprCode(Parse *pParse, Expr *pExpr, int target){
  int inReg;

  assert( target>0 && target<=pParse->nMem );
  if( pExpr && pExpr->op==TK_REGISTER ){
    sqlite3VdbeAddOp2(pParse->pVdbe, OP_Copy, pExpr->iTable, target);
  }else{
    inReg = sqlite3ExprCodeTarget(pParse, pExpr, target);
    assert( pParse->pVdbe || pParse->db->mallocFailed );
    if( inReg!=target && pParse->pVdbe ){
      sqlite3VdbeAddOp2(pParse->pVdbe, OP_SCopy, inReg, target);
    }
  }
  return target;
}

/*
** Generate code that evalutes the given expression and puts the result
** in register target.

      int regTemp = sqlite3GetTempRange(pParse, nCol);
      int regRec = sqlite3GetTempReg(pParse);
      KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx);
  
      sqlite3VdbeAddOp3(v, OP_OpenRead, iCur, pIdx->tnum, iDb);
      sqlite3VdbeChangeP4(v, -1, (char*)pKey, P4_KEYINFO_HANDOFF);
      for(i=0; i<nCol; i++){
        sqlite3VdbeAddOp2(v, OP_Copy, aiCol[i]+1+regData, regTemp+i);
      }
  
      /* If the parent table is the same as the child table, and we are about
      ** to increment the constraint-counter (i.e. this is an INSERT operation),
      ** then check if the row being inserted matches itself. If so, do not
      ** increment the constraint-counter.  */
      if( pTab==pFKey->pFrom && nIncr==1 ){

  /* Make sure the results of the current row are \000 terminated
  ** and have an assigned type.  The results are de-ephemeralized as
  ** as side effect.
  */
  pMem = p->pResultSet = &aMem[pOp->p1];
  for(i=0; i<pOp->p2; i++){
    assert( memIsValid(&pMem[i]) );
    Deephemeralize(&pMem[i]);
    sqlite3VdbeMemNulTerminate(&pMem[i]);
    sqlite3VdbeMemStoreType(&pMem[i]);
    REGISTER_TRACE(pOp->p1+i, &pMem[i]);
  }
  if( db->mallocFailed ) goto no_mem;

  /* Return SQLITE_ROW

  sqlite3_context ctx;
  sqlite3_value **apVal;
  int n;

  n = pOp->p5;
  apVal = p->apArg;
  assert( apVal || n==0 );
  assert( pOp->p3>0 && pOp->p3<=p->nMem );
  pOut = &aMem[pOp->p3];
  memAboutToChange(p, pOut);

  assert( n==0 || (pOp->p2>0 && pOp->p2+n<=p->nMem+1) );
  assert( pOp->p3<pOp->p2 || pOp->p3>=pOp->p2+n );
  pArg = &aMem[pOp->p2];
  for(i=0; i<n; i++, pArg++){
    assert( memIsValid(pArg) );
    apVal[i] = pArg;
    Deephemeralize(pArg);
    sqlite3VdbeMemStoreType(pArg);
    REGISTER_TRACE(pOp->p2+i, pArg);
  }

  assert( pOp->p4type==P4_FUNCDEF || pOp->p4type==P4_VDBEFUNC );
  if( pOp->p4type==P4_FUNCDEF ){
    ctx.pFunc = pOp->p4.pFunc;
    ctx.pVdbeFunc = 0;
  }else{
    ctx.pVdbeFunc = (VdbeFunc*)pOp->p4.pVdbeFunc;
    ctx.pFunc = ctx.pVdbeFunc->pFunc;
  }




  ctx.s.flags = MEM_Null;
  ctx.s.db = db;
  ctx.s.xDel = 0;
  ctx.s.zMalloc = 0;

  /* The output cell may already have a buffer allocated. Move
  ** the pointer to ctx.s so in case the user-function can use

  if( (f&(MEM_Str|MEM_Blob)) && pMem->z!=pMem->zMalloc ){
    if( sqlite3VdbeMemGrow(pMem, pMem->n + 2, 1) ){
      return SQLITE_NOMEM;
    }
    pMem->z[pMem->n] = 0;
    pMem->z[pMem->n+1] = 0;
    pMem->flags |= MEM_Term;
#ifdef SQLITE_DEBUG
    pMem->pScopyFrom = 0;
#endif
  }

  return SQLITE_OK;
}

/*
** If the given Mem* has a zero-filled tail, turn it into an ordinary