t/io/eintr.t: Skip some tests on pre-16 Darwin.

The tests where we write a string larger than the pipe size to
a pipe hang on 15.6.0, while they seem to work on Darwin 17.7.0.
So we will skip these tests on Darwin, if the major version is
less than 16. (We may adjust this is we have more reports on
which versions between 15.6.0 and 17.7.0 success/fail).

Note that the tests hang even if we send a string of 512 characters,
which is much, much smaller than the actual size of the string in
the test.

Author: Abigail

t/io/eintr.t

@@ -59,6 +59,8 @@ if ($^O eq 'VMS' || $^O eq 'MSWin32' || $^O eq 'cygwin' || $^O =~ /freebsd/ || $
 	exit 0;
 }
 
+
+
 my ($in, $out, $st, $sigst, $buf);
 
 plan(tests => 10);
@@ -96,60 +98,65 @@ alarm(0);
 ok(!$st, 'read/die: read status');
 ok(close($in), 'read/die: close status');
 
-# This used to be 1_000_000, but on Linux/ppc64 (POWER7) this kept
-# consistently failing. At exactly 0x100000 it started passing
-# again. Now we're asking the kernel what the pipe buffer is, and if
-# that fails, hoping this number is bigger than any pipe buffer.
-my $surely_this_arbitrary_number_is_fine = (eval {
-    use Fcntl qw(F_GETPIPE_SZ);
-    fcntl($out, F_GETPIPE_SZ, 0);
-} || 0xfffff) + 1;
-
-# close during print
-
-fresh_io;
-$SIG{ALRM} = sub { $sigst = close($out) ? "ok" : "nok" };
-$buf = "a" x $surely_this_arbitrary_number_is_fine . "\n";
-select $out; $| = 1; select STDOUT;
-alarm(1);
-$st = print $out $buf;
-alarm(0);
-is($sigst, 'nok', 'print/close: sig handler close status');
-ok(!$st, 'print/close: print status');
-ok(!close($out), 'print/close: close status');
-
-# die during print
-
-fresh_io;
-$SIG{ALRM} = sub { die };
-$buf = "a" x $surely_this_arbitrary_number_is_fine . "\n";
-select $out; $| = 1; select STDOUT;
-alarm(1);
-$st = eval { print $out $buf };
-alarm(0);
-ok(!$st, 'print/die: print status');
-# the close will hang since there's data to flush, so use alarm
-alarm(1);
-ok(!eval {close($out)}, 'print/die: close status');
-alarm(0);
-
-# close during close
-
-# Apparently there's nothing in standard Linux that can cause an
-# EINTR in close(2); but run the code below just in case it does on some
-# platform, just to see if it segfaults.
-fresh_io;
-$SIG{ALRM} = sub { $sigst = close($in) ? "ok" : "nok" };
-alarm(1);
-close $in;
-alarm(0);
-
-# die during close
-
-fresh_io;
-$SIG{ALRM} = sub { die };
-alarm(1);
-eval { close $in };
-alarm(0);
+SKIP: {
+    skip "Tests hang on older versions of Darwin", 5
+          if $^O eq 'darwin' && $osmajmin < 16;
+
+    # This used to be 1_000_000, but on Linux/ppc64 (POWER7) this kept
+    # consistently failing. At exactly 0x100000 it started passing
+    # again. Now we're asking the kernel what the pipe buffer is, and if
+    # that fails, hoping this number is bigger than any pipe buffer.
+    my $surely_this_arbitrary_number_is_fine = (eval {
+        use Fcntl qw(F_GETPIPE_SZ);
+        fcntl($out, F_GETPIPE_SZ, 0);
+    } || 0xfffff) + 1;
+
+    # close during print
+
+    fresh_io;
+    $SIG{ALRM} = sub { $sigst = close($out) ? "ok" : "nok" };
+    $buf = "a" x $surely_this_arbitrary_number_is_fine . "\n";
+    select $out; $| = 1; select STDOUT;
+    alarm(1);
+    $st = print $out $buf;
+    alarm(0);
+    is($sigst, 'nok', 'print/close: sig handler close status');
+    ok(!$st, 'print/close: print status');
+    ok(!close($out), 'print/close: close status');
+
+    # die during print
+
+    fresh_io;
+    $SIG{ALRM} = sub { die };
+    $buf = "a" x $surely_this_arbitrary_number_is_fine . "\n";
+    select $out; $| = 1; select STDOUT;
+    alarm(1);
+    $st = eval { print $out $buf };
+    alarm(0);
+    ok(!$st, 'print/die: print status');
+    # the close will hang since there's data to flush, so use alarm
+    alarm(1);
+    ok(!eval {close($out)}, 'print/die: close status');
+    alarm(0);
+
+    # close during close
+
+    # Apparently there's nothing in standard Linux that can cause an
+    # EINTR in close(2); but run the code below just in case it does on some
+    # platform, just to see if it segfaults.
+    fresh_io;
+    $SIG{ALRM} = sub { $sigst = close($in) ? "ok" : "nok" };
+    alarm(1);
+    close $in;
+    alarm(0);
+
+    # die during close
+
+    fresh_io;
+    $SIG{ALRM} = sub { die };
+    alarm(1);
+    eval { close $in };
+    alarm(0);
+}
 
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