perl: redirect stderr to /dev/null instead of closing

On my system, t9100.1 triggers the following warning:

==352== Syscall param write(buf) points to uninitialised byte(s)
==352==    at 0x57119C0: __write_nocancel (in /lib64/libc-2.17.so)
==352==    by 0x56AC1D2: _IO_file_write@@GLIBC_2.2.5 (in /lib64/libc-2.17.so)
==352==    by 0x56AC0B1: new_do_write (in /lib64/libc-2.17.so)
==352==    by 0x56AD3B4: _IO_do_write@@GLIBC_2.2.5 (in /lib64/libc-2.17.so)
==352==    by 0x56AD6FE: _IO_file_overflow@@GLIBC_2.2.5 (in /lib64/libc-2.17.so)
==352==    by 0x56AE3D8: _IO_default_xsputn (in /lib64/libc-2.17.so)
==352==    by 0x56ACAA2: _IO_file_xsputn@@GLIBC_2.2.5 (in /lib64/libc-2.17.so)
==352==    by 0x5682133: buffered_vfprintf (in /lib64/libc-2.17.so)
==352==    by 0x567CE9D: vfprintf (in /lib64/libc-2.17.so)
==352==    by 0x5687096: fprintf (in /lib64/libc-2.17.so)
==352==    by 0x4E7AC5: vreportf (usage.c:15)
==352==    by 0x4E7B14: die_builtin (usage.c:38)

The actual complaint appears to be a bug in the underlying
implementation.  What's interesting here is that it is apparently
_triggered_ by closing stderr, which results in (from strace)

write(2, "fatal: Needed a single revision\n", 32) = -1 EBADF (Bad file descriptor)
write(2, "\0", 1) = -1 EBADF (Bad file descriptor)

Closing stderr is a bad idea anyway: there is a very real chance that
we print fatal error messages to some other file that just happens to
be opened on the now-free FD 2.  So let's not do that.

As pointed out by Eric Wong (thanks), the initial close needs to go:
die() would again write nowhere if we close STDERR beforehand.

Signed-off-by: Thomas Rast <trast@inf.ethz.ch>
Signed-off-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/perl/Git.pm b/perl/Git.pm
index 57a17160f9decb7879b8d6cba741ddb6d593be47..4778428830a5eaf6fb9773b18a18f02f934c8820 100644 (file)
--- a/perl/Git.pm
+++ b/perl/Git.pm
@@ -1335,12 +1335,12 @@ sub _command_common_pipe {
                if (not defined $pid) {
                        throw Error::Simple("open failed: $!");
                } elsif ($pid == 0) {
-                       if (defined $opts{STDERR}) {
-                               close STDERR;
-                       }
                        if ($opts{STDERR}) {
                                open (STDERR, '>&', $opts{STDERR})
                                        or die "dup failed: $!";
+                       } elsif (defined $opts{STDERR}) {
+                               open (STDERR, '>', '/dev/null')
+                                       or die "opening /dev/null failed: $!";
                        }
                        _cmd_exec($self, $cmd, @args);
                }