bug#67540: 29.1; Emacs on Windows incorrectly capitalizes some environment variables

[Eli Zaretskii]

> Date: Wed, 29 Nov 2023 19:42:46 -0800
> From: Jim Porter <jporterbugs@gmail.com>
> 
> On 11/29/2023 6:29 PM, Dave Abrahams wrote:
> > Now issue the "set" command from a CMD shell. Notice that the "Path"
> > environment variable has been renamed to "PATH" in Emacs.  This renaming
> > interferes with some tools operating correctly e.g. the swift compiler
> > (see https://swift.org).
> 
> This sounds like there's a bug in the Swift compiler. Environment 
> variables on MS-Windows are case-insensitive: 
> <https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/getenv-wgetenv?view=msvc-170>.
>  
> That documentation just covers 'getenv' (and 'wgetenv'), but I'm 
> reasonably certain the same applies to the Win32 APIs as well.

Right.

> It might be nice for Emacs to preserve the case of any existing 
> environment variables on MS-Windows to be on the safe side though...

That's impossible in practice: we'd need to "fix" every single Lisp
program and every place in the Emacs C code that compare against
"PATH" case-sensitively.  And what about user confusion, for those of
us who mostly work on Unix, but sometimes need to work on Windows?

We decided long ago to make these letter-case changes in the Windows
build of Emacs, and the decision held well since then.  I see no
reason to change that decision now, just because some program
misbehaves on Windows.