Question

Using the code below in order to get names of my drives:

const DWORD buffer_length = sizeof(DWORD)*CHAR_BIT;
WCHAR buffer[buffer_length] = {0};
GetLogicalDriveStrings(buffer_length,buffer);
std::set<wchar_t> drives_letters;
for(auto e : buffer)
{
    drives_letters.insert(e);
}  

I’m getting following output as a result (looping over drives_letters):

: //what on earth is this?  
C 
D 
E 
F 
G 
I 
\ //and what on earth is this?  

Answer 1

GetLogicalDriveStrings returns strings in the form C:\. This can be inferred from this documentation passage:

Each string in the buffer may be used wherever a root directory is
required, such as for the GetDriveType and GetDiskFreeSpace functions.

Since you are putting these characters into a set, which disallows duplicates, you end up with all the different drive letters plus one copy of a double colon and a backslash. And the reason that the colon prints first and the backslash last is that std::set is inherently ordered, so the ASCII codes of each character decide.