[CMake] Strange issue with 3.14.0 and copying files

[Ron Olson]

Hi all-

As a way of introduction, I’m Ron, and I maintain Apple’s Swift 
programming language package for Fedora. I’ve been tracking down a 
build failure and I came across a weird issue using 3.14.0 that 
doesn’t seem to be a problem on 3.12.1. If you copy a file to the same 
location, it overwrites it with a zero byte file:

[rolson at testn temp]$ cmake --version
cmake version 3.14.0

CMake suite maintained and supported by Kitware (kitware.com/cmake).

[rolson at testn temp]$ echo "hello world" > foo.txt

[rolson at testn temp]$ ls -lah
total 8.0K
drwxrwxr-x. 2 rolson rolson   21 Mar 20 16:39 .
drwx------. 9 rolson rolson 4.0K Mar 20 16:22 ..
-rw-rw-r--. 1 rolson rolson   12 Mar 20 16:39 foo.txt

[rolson at testn temp]$ cmake -E copy foo.txt .

[rolson at testn temp]$ ls -lah
total 4.0K
drwxrwxr-x. 2 rolson rolson   21 Mar 20 16:39 .
drwx------. 9 rolson rolson 4.0K Mar 20 16:22 ..
-rw-rw-r--. 1 rolson rolson    0 Mar 20 16:39 foo.txt

I haven’t been able to find any documentation about whether this is 
expected behavior or not; under 3.12.1 the result would be foo.txt would 
remain untouched.

If it’s a bug, I’ll file a report, but wanted to make sure it is 
before I do so.

Ron