[PATCH v2 1/2] Allow deriving the current user's home directory via the HOME variable

Corinna Vinschen corinna-cygwin@cygwin.com
Tue Oct 18 17:02:50 GMT 2022

Hi Johannes,

On Sep 21 13:58, Johannes Schindelin wrote:
> Hi Corinna,
> sorry for the blast from the past, but I am renewing my efforts to
> upstream Git for Windows' patches that can be upstreamed.
> On Thu, 17 Dec 2015, Corinna Vinschen wrote:

Well, not even 7 years, so what? :)

> > On Dec 17 19:05, Johannes Schindelin wrote:
> > > +  DWORD max = sizeof wbuf / sizeof *wbuf;
> > > +  DWORD len = GetEnvironmentVariableW (key, wbuf, max);
> >
> > This call to GetEnvironmentVariableW looks gratuitous to me.  Why don't
> > you simply call getenv?  It did the entire job already, it avoids the
> > requirement for a local buffer, and in case of $HOME it even did the
> > Win32->POSIX path conversion.  If there's a really good reason for using
> > GetEnvironmentVariableW it begs at least for a longish comment.
> My only worry is that `getenv("HOME")` might receive a "Cygwin-ified"
> version of the value. That is, `getenv("HOME")` might return something
> like `/cygdrive/c/Users/corinna` when we expect it to return
> `C:\Users\corinna` instead.

Haha, yeah, that's exactly what it does.  Look at environ.cc, search for
conv_envvars.  There's a list of env vars which are converted
automatically.  So getenv ("HOME") already does what you need, you just
have to adapt the code accordingly, i. e.

  if ((home = getenv ("HOME")))
    return strdup (home);
  if (((home_drive = getenv ("HOMEDRIVE")
    return (char *) cygwin_create_path (CCP_WIN_A_TO_POSIX, home);

However, on second thought, I wonder if the HOMEDRIVE/HOMEPATH/USERPROFILE
code is really required.  AFAICS, it's just a duplication of the effort
already done in fetch_windows_home(), isn't it?

HOMEDRIVE/HOMEPATH are generated from the DB data returned in
USER_INFO_3 or via ldap anyway, and fetch_windows_home() also falls back
to fetching the user profile path, albeit from the registry.

That means, the results from the "env" method is equivalent to the
"windows" method, just after checking $HOME.  That's a bit of a downer.

Assuming the "env" method would *only* check for $HOME, the user would
have the same result by simply setting nsswitch.conf accordingly:

  home: env windows


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