[perl #77672] avoid a file handle redirection race

With multiple threads (and Win32 fork() is implemented in terms of
threads), Win32's popen() code had a race condition where a different
thread could write to the stdout (or read from the stdin) handle setup
for a child process.

Avoid this by using the Win32 API to supply the I/O handles instead of
redirecting them in the current process.

1 files changed, 27 insertions, 0 deletions

diff --git a/t/win32/popen.t b/t/win32/popen.t
new file mode 100644
index 0000000000..eca0a1d67c
--- /dev/null
+++ b/t/win32/popen.t
@@ -0,0 +1,27 @@
+#!./perl
+
+BEGIN {
+    chdir 't' if -d 't';
+    @INC = '../lib';
+    require "./test.pl";
+    require Config;
+    $Config::Config{d_pseudofork}
+        or skip_all("no psuedo-fork");
+    eval 'use Errno';
+    die $@ if $@ and !is_miniperl();
+}
+
+# [perl #77672] backticks capture text printed to stdout when working
+# with multiple threads on windows
+watchdog(20); # before the fix this would often lock up
+
+fresh_perl_like(<<'PERL', qr/\A[z\n]+\z/, {}, "popen and threads");
+if (!defined fork) { die "can't fork" }
+for(1..100) {
+  print "zzzzzzzzzzzzz\n";
+  my $r=`perl -v`;
+  print $r if($r=~/zzzzzzzzzzzzz/);
+}
+PERL
+
+done_testing();