FindFirstFile LPCSTR - c++

Question

Hello i got a problem with my code here.
LPCSTR mergeString(LPCSTR firstString, std::string secondString)
{
string convertedString = ConvertString(firstString);
LPCSTR mergedString;
int i = convertedString.size();
convertedString.insert(i, secondString);
mergedString = (convertedString.c_str());
return mergedString;
}
void GetFiles(LPCSTR path)
{
WIN32_FIND_DATA File_Data;
LPCSTR lPath = mergeString(path,"\\*.txt");
FindFirstFile(lPath, &File_Data);
wcout << File_Data.cFileName;
}
You pass in the path you want to use in the GetFiles(LPCSTR path) Then i use the mergestring function to merge together the path with a extension (\*.txt) everything works except when it returns the LPCSTR then its just a lot of wierd characters and i dont know why or is it a better way to do this?

Answer 1

Your code is unnecessarily complicated.
If you just want to add a \*.txt suffix to the input path string, you can simply use std::string with its overloaded operator+.
Then, if you want to pass a std::string to a Win32 API that has a const char* (i.e. LPCSTR) parameter, you can use std::string::c_str() method:
void GetFiles(LPCSTR path)
{
WIN32_FIND_DATA fileData;
std::string searchPath(path);
searchPath += "\\*.txt";
FindFirstFile(searchPath.c_str(), &fileData);
wcout << fileData.cFileName;
}
Note also that in modern world you should use Unicode (UTF-16) for Win32 programming; so const wchar_t* and std::wstring are better options than const char* and std::string.
Moreover, I'd just use a std::wstring class as parameter, instead of a raw wchar_t pointer.
void GetFiles(const std::wstring& path)
{
std::wstring searchPath = path + L"\\*.txt";
WIN32_FIND_DATA fileData;
FindFirstFile(searchPath.c_str(), &fileData);
std::wcout << fileData.cFileName;
}

Answer 2

Your GetFiles function is returning a pointer to memory which is no longer valid, File_Data.cFileName can only be used in GetFiles because that's where File_Data is defined. The simplest solution is to use the C++ string classstd::string.
std::string GetFiles(LPCSTR path)
{
WIN32_FIND_DATA File_Data;
LPCSTR lPath = mergeString(path,"\\*.txt");
FindFirstFile(lPath, &File_Data);
return File_Data.cFileName;
}
Using pointers unnecessarily is a bad habit to get into, for this kind of reason (any many more).
Your mergeString function should also be rewritten with fewer pointers.
std::string mergeString(LPCSTR firstString, std::string secondString)
{
string convertedString = ConvertString(firstString);
int i = convertedString.size();
convertedString.insert(i, secondString);
return convertedString;
}