bug#37445: 27.0.50; Permission denied after make install

[Paul Eggert <eggert@cs.ucla.edu>]

On 9/18/19 2:02 AM, Tino Calancha wrote:

> # Install Emacs w/ the first user
> $ whoami
> ec2-user
> $ cd ~/soft/emacs-master
> $ make && sudo make install
> # Launch Emasc w/ the second user
> $ su user_foo
> $ cd
> $ emacs
> emacs: Reading symbolic link: Permission denied, /home/ec2-user/soft

This appears to be a configuration error in how Emacs master starts up. 
Apparently if you build Emacs in (say) /tmp/foo and then install Emacs, the 
Emacs you install consults files in /tmp/foo during startup. After you remove 
/tmp/foo, someone else can create a /tmp/foo and hijack anybody who starts up 
the installed Emacs.

I papered over the problem with commit 2019-09-18T11:21:19Z!eggert@cs.ucla.edu 
(735940f4551a43f3b4381105dc074cd7d494f2f3), which suppresses the diagnostic and 
let Emacs continue to run. However, the configuration error remains and I will 
try to squeeze free time to look at it.

I should be able to reproduce the original problem by compiling with 
-DPICKY_EACCES. That is, the idea is to use -DPICKY_EACCES to debug longstanding 
bugs in Emacs that we otherwise might not have discovered.