How to correct store LPTSTR in map - c++

Question

I need to store values from registry in map. I have such code:
map<int, LPTSTR> mymap;
for (i = 0, retCode = ERROR_SUCCESS; i<cValues; i++)
{
cchValue = MAX_VALUE_NAME;
achValue[0] = '\0';
retCode = RegEnumValue(hKey, i,
achValue,
&cchValue,
NULL,
NULL,
NULL,
NULL);
if (retCode == ERROR_SUCCESS)
{
DWORD lpData = cbMaxValueData;
buffer[0] = '\0';
LONG dwRes = RegQueryValueEx(hKey, achValue, 0, NULL, buffer, &lpData);
LPTSTR val = (TCHAR*)buffer;
MessageBox(NULL, val, L"VALUE", MB_OK);
auto r = mymap.insert(pair<int, LPTSTR>(i, val));
for (map<int, LPTSTR>::const_iterator it = mymap.begin(); it != mymap.end(); it++)
{
wchar_t szMessage2[1300];
if (SUCCEEDED(StringCchPrintf(szMessage2, ARRAYSIZE(szMessage2), L"+ %d : %s\n", it->first, it->second)))
{
MessageBox(NULL, szMessage2, L"MAP", MB_OK);
}
}
}
}
How to correct save val to map? Right now all keys have the same value (latest).

Answer 1

The problem is that you have a single buffer that you are reusing during enumeration, and you are storing just a pointer to that buffer into your map. So every entry will be pointing at the same physical memory, which contains the last piece of data written to it.
You need to store copies of the enumerated string data into your map. Use std::string/std::wstring for that, eg:
using tstring = basic_string<TCHAR>;
map<int, tstring> mymap;
for (i = 0, retCode = ERROR_SUCCESS; i < cValues; i++)
{
cchValue = MAX_VALUE_NAME;
retCode = RegEnumValue(hKey, i,
achValue,
&cchValue,
NULL,
NULL,
NULL,
NULL);
if (retCode == ERROR_SUCCESS)
{
DWORD dwData = cbMaxValueData;
DWORD dwType = 0;
LONG dwRes = RegQueryValueEx(hKey, achValue, 0, &dwType, buffer, &dwData);
if (dwRes == ERROR_SUCCESS)
{
switch (dwType)
{
case REG_SZ:
case REG_MULTI_SZ:
case REG_EXPAND_SZ:
{
tstring val((LPTSTR)buffer, dwData / sizeof(TCHAR));
//MessageBox(NULL, val.c_str(), TEXT("VALUE"), MB_OK);
mymap.insert(make_pair(i, val));
break;
}
}
}
}
}
for (auto &value: mymap)
{
TCHAR szMessage2[1300];
if (SUCCEEDED(StringCchPrintf(szMessage2, ARRAYSIZE(szMessage2), TEXT("+ %d : %s\n"), value.first, value.second.c_str())))
{
MessageBox(NULL, szMessage2, TEXT("MAP"), MB_OK);
}
}
However, since you are clearly compiling with UNICODE enabled, you shouldn't be using TCHAR at all:
map<int, wstring> mymap;
for (i = 0, retCode = ERROR_SUCCESS; i < cValues; i++)
{
cchValue = MAX_VALUE_NAME;
retCode = RegEnumValueW(hKey, i,
achValue,
&cchValue,
NULL,
NULL,
NULL,
NULL);
if (retCode == ERROR_SUCCESS)
{
DWORD dwData = cbMaxValueData;
DWORD dwType = 0;
LONG dwRes = RegQueryValueExW(hKey, achValue, 0, &dwType, buffer, &dwData);
if (dwRes == ERROR_SUCCESS)
{
switch (dwType)
{
case REG_SZ:
case REG_MULTI_SZ:
case REG_EXPAND_SZ:
{
wstring val((LPWSTR)buffer, dwData / sizeof(WCHAR));
//MessageBoxW(NULL, val.c_str(), L"VALUE", MB_OK);
mymap.insert(make_pair(i, val));
break;
}
}
}
}
}
for (auto &value: mymap)
{
WCHAR szMessage2[1300];
if (SUCCEEDED(StringCchPrintfW(szMessage2, ARRAYSIZE(szMessage2), L"+ %d : %s\n", value.first, value.second.c_str())))
{
MessageBoxW(NULL, szMessage2, L"MAP", MB_OK);
}
}