Trying to replace delete pointer call with std::unique_ptr call - visual-c++

Question

I am getting myself confused again with unique pointers and deletion.
I am trying to avoid the need for the delete pWidth line below:
void CCreateReportDlg::DeleteColumnWidthMap(CMapWordToPtr& rMapColumnWidth)
{
WORD wColumn{}, * pWidth = nullptr;
auto sPos = rMapColumnWidth.GetStartPosition();
while (sPos != nullptr)
{
rMapColumnWidth.GetNextAssoc(sPos, wColumn, reinterpret_cast<void*&>(pWidth));
if (pWidth != nullptr)
{
//delete pWidth;
std::unique_ptr<WORD*> cleanup(pWidth);
}
}
rMapColumnWidth.RemoveAll();
}
Why is it saying this?
Ah, I think I now see that the unique_ptr is supposed to be an array of WORD pointers. But I only have just the one value.
Update
Example of how I populate the map (parameter to function):
void CCreateReportDlg::HideColumns(CGridCtrl* pGrid, const CDWordArray* pAryDWColumns, CMapWordToPtr& rMapColumnWidth)
{
ASSERT(pGrid != nullptr);
ASSERT(pAryDWColumns != nullptr);
if (pGrid == nullptr || pAryDWColumns == nullptr)
return;
DeleteColumnWidthMap(rMapColumnWidth);
const auto iSize = pAryDWColumns->GetSize();
for (INT_PTR i = 0; i < iSize; i++)
{
const auto dwColumnData = pAryDWColumns->GetAt(i);
const auto iCol = LOWORD(dwColumnData);
const auto eImage = static_cast<CheckImageIndex>(HIWORD(dwColumnData));
if (eImage == CheckImageIndex::Unchecked)
{
auto pWidth = std::make_unique<WORD>().release();
ASSERT(pWidth != nullptr);
if (pWidth != nullptr)
{
*pWidth = pGrid->GetColumnWidth(iCol);
rMapColumnWidth.SetAt(iCol, pWidth);
}
pGrid->SetColumnWidth(iCol, 0);
}
}
}

Answer 1

Use {std::unique_ptr<WORD> cleanup(pWidth);} for deleting pWidth = std::make_unique<WORD>().release();
But std::map<int,int> (or unordered_map) is a much better than CMapWordToPtr, you don't need to store a pointer here.
You should be able to simplify your function like this:
void HideColumns(CGridCtrl* pGrid,
std::vector<DWORD> &pAryDWColumns, std::map<int,int> &rMapColumnWidth)
{
//clear the map, it doesn't need separate function
rMapColumnWidth.clear();
for (auto dword : pAryDWColumns)
{
const auto iCol = LOWORD(dword);
const auto eImage = static_cast<CheckImageIndex>(HIWORD(dword));
if (eImage == CheckImageIndex::Unchecked)
{
rMapColumnWidth[iCol] = pGrid->GetColumnWidth(iCol);
pGrid->SetColumnWidth(iCol, 0);
}
pGrid->SetColumnWidth(iCol, 0);
}
}
...
for (auto e : map)
TRACE("%d\n", e);
By the way, in another question I think I recommended using std::unique_ptr to turn off some Code Analysis messages. You should ignore that advice. Either stick with new/delete or use STL classes which have automatic memory management.
You can still use std::unique_ptr in some special cases, for example when passing data to APIs or some MFC functions.