Re: 'make check' fails due to old perl on cygwin

Hi Denis,

Thanks for the report.  Does this address the problem?

commit 97f7448883bb6ef47d777b0f89e981998e76dcf2
Author: Akim Demaille <[email protected]>
Date:   Fri Nov 15 18:10:34 2019 +0100

    tests: be robust to old Perl versions on Cygwin
    
    Reported by Denis Excoffier.
    https://lists.gnu.org/archive/html/bug-bison/2019-11/msg00008.html.
    
    * tests/output.at: Be sure to remove back up files.

diff --git a/tests/output.at b/tests/output.at
index 54214eaa..c9451498 100644
--- a/tests/output.at
+++ b/tests/output.at
@@ -47,8 +47,12 @@ done
 foo: '0' {};
 ]])
 
-# There is not AT_DATA_UNQUOTED.
-AT_PERL_REQUIRE([-pi -e 's{\$at_dir}'"{$at_group_dir}g" $1])
+# There is no AT_DATA_UNQUOTED.
+if $EGREP 'at_dir' $1 >/dev/null; then
+   AT_PERL_REQUIRE([-pi -e 's{\$at_dir}'"{$at_group_dir}g" $1])
+   # On Cygwin, up to Perl 5.28, 'perl -pi' left a foo.bak file.
+   AT_CHECK([rm -f $1.bak])
+fi
 
 
 AT_BISON_CHECK([$3 $1], [$5], [], [ignore])[