How to convert WCHAR* to string in C++ and vice versa? - c++

Question

I tried to convert wchar* to string. First I made it as wstring. This method is specified in stackoverflow when I search. But it doesn't work for my part. What's wrong with it?
GetProcessImageNameFromPID.cpp
BOOL GetProcessImageNameFromPID::getProcessNameFromProcessID(DWORD processId, WCHAR**processName)
{
HANDLE hProcessSnap;
HANDLE hProcess;
PROCESSENTRY32 pe32;
DWORD dwPriorityClass;
// Take a snapshot of all processes in the system.
hProcessSnap = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
if (hProcessSnap == INVALID_HANDLE_VALUE)
{
printError(TEXT("CreateToolhelp32Snapshot (of processes)"));
return(FALSE);
}
// Set the size of the structure before using it.
pe32.dwSize = sizeof(PROCESSENTRY32);
// Retrieve information about the first process,
// and exit if unsuccessful
if (!Process32First(hProcessSnap, &pe32))
{
printError(TEXT("Process32First")); // show cause of failure
CloseHandle(hProcessSnap); // clean the snapshot object
return(FALSE);
}
// Now walk the snapshot of processes, and
// display information about each process in turn
int i = 0;
do
{
WCHAR*allprocessName = pe32.szExeFile;
//_tprintf( TEXT("\n%d)PROCESS NAME: %s"), i, allprocessName);
// Retrieve the priority class.
dwPriorityClass = 0;
hProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pe32.th32ProcessID);
if (hProcess == NULL)
printError(TEXT("OpenProcess"));
else
{
dwPriorityClass = GetPriorityClass(hProcess);
if (!dwPriorityClass)
printError(TEXT("GetPriorityClass"));
CloseHandle(hProcess);
}
DWORD pid = pe32.th32ProcessID;
//_tprintf( TEXT("\n Process ID = %d"), pid );
if (pid == processId)
{
*processName = allprocessName;
//_tprintf( TEXT("Inside Method:\n"));
_tprintf(TEXT("PROCESS NAME: %s\n\n"), *processName);
return TRUE;
}
i++;
} while (Process32Next(hProcessSnap, &pe32));
CloseHandle(hProcessSnap);
return(FALSE);
}
int _tmain(int argc, _TCHAR* argv[])
{
WCHAR**processName = (WCHAR**)malloc(sizeof(WCHAR));
GetProcessImageNameFromPID::getProcessNameFromProcessID(4, processName);
_tprintf(TEXT("PROCESS NAME: %s\n\n"), *processName); // correct
GetProcessImageNameFromPID::getProcessNameFromProcessID(executionProcessID, processName);
wstring ws(*processName);
string str(ws.begin(), ws.end());
processImageName = str;
cout << processImageName << endl; // some wrong characters are printed
}

Answer 1

There are various problems with your code, the last one is the most serious:
This looks strange:
WCHAR**processName = (WCHAR**)malloc(sizeof(WCHAR));
I suppose you want a pointer to WCHAR*, why dont you:
WCHAR* processName;
and then:
GetProcessImageNameFromPID::getProcessNameFromProcessID(4, &processName);
^~~~~ !!
What is the type of processImageName? What is the name of the process, if it contains non ASCII chars then your conversion code will give wrong characters.
Another is that code:
*processName = allprocessName;
is making *processName equal to pointer which is dangling pointer after your function ends, it points to WCHAR array in:
PROCESSENTRY32 pe32;
which is created on stack.
What you should do is make processName an array:
WCHAR processName[MAX_PATH];
and inside your function copy process name from pe32 to this array.