bug#31003: Test failure on macOS with new Xcode 9.3 command-line tools

[Paul Eggert]

Charles Diza wrote:

> I'm really wondering whether a grep 3.1 that fails this test is safe to
> keep using.

It's safe. This is an incompatibility that Apple deliberately introduced into 
macOS to try to make programs "safer". The incompatibility breaks the test 
programs in question but does not break grep or diffutils proper (nor does it 
make them any "safer"). We'll work around the incompatiblity in future versions. 
See the thread starting here:

https://lists.gnu.org/r/bug-gnulib/2017-07/msg00056.html