Question

Well, today; I’ve come across a strange little situation with e.g. char* cFileCopy = strDrive; _

This should make cFileCopy hold the value of strDrive only at this point, which it does, however when I use strcat(cFileCopy, cFileName);

the value of strDrive also changes to the value of cFileCopy after strcat()

_

I’m not sure what’s happening, but here’s the code if anybody could shed a little light on the situation.

DWORD dwDrives = GetLogicalDrives();
char strDrive[3];

for(int i = 0; i<26; i++)
{
    wsprintf(strDrive, "%c:\\", 'A'+i);
    if(GetDriveType(strDrive) == DRIVE_REMOVABLE)
    {
        char* cFileName = new char[11];
        cFileName = "test.txt";
        char* cFileCopy = strDrive;
        strcat(cFileCopy, cFileName);
        MessageBox(NULL, strDrive, "Strange", MB_OK); //MSG - This shows drive:\test.txt when it should show only drive:\/
        MessageBox(NULL, cFileCopy, "OK", MB_OK); //MSG - This should be showing drive:\test.txt, which it does.
    }
}

Any help is appreciated, Thank you.

Answer 1

You need to revisit how pointers work – if you point two variables to the same memory (as here), then a modification to the memory pointed to by one will also change the value pointedd to by the other.

Note that you are also overflowing the 3 byte strDrive buffer handily in that strcat call, which will result in obscure bugs surfacing down the line. There is also a leak of cFileName which has no delete[] call to match the new[] (use smart pointers or std::string instead to simplify this).

If you want the semantics you expect, you should be using C++ std::string, not raw pointers.