perl/t/io/eintr.t

#!./perl

# If a read or write is interrupted by a signal, Perl will call the
# signal handler and then attempt to restart the call. If the handler does
# something nasty like close the handle or pop layers, make sure that the
# read/write handles this gracefully (for some definition of 'graceful':
# principally, don't segfault).

BEGIN {
    chdir 't' if -d 't';
    require './test.pl';
    set_up_inc('../lib');
    skip_all_without_dynamic_extension('Fcntl');
}

use warnings;
use strict;
use Config;

my $piped;
eval {
    pipe my $in, my $out;
    $piped = 1;
};
if (!$piped) {
    skip_all('pipe not implemented');
    exit 0;
}
unless (exists  $Config{'d_alarm'}) {
    skip_all('alarm not implemented');
    exit 0;
}

# XXX for some reason the stdio layer doesn't seem to interrupt
# write system call when the alarm triggers.  This makes the tests
# hang.

if (exists $ENV{PERLIO} && $ENV{PERLIO} =~ /stdio/  ) {
    skip_all('stdio not supported for this script');
    exit 0;
}

# on Win32, alarm() won't interrupt the read/write call.
# Similar issues with VMS.
# On FreeBSD, writes to pipes of 8192 bytes or more use a mechanism
# that is not interruptible (see perl #85842 and #84688).
# "close during print" also hangs on Solaris 8 (but not 10 or 11).
#
# Also skip on release builds, to avoid other possibly problematic
# platforms

my ($osmajmin) = $Config{osvers} =~ /^(\d+\.\d+)/;
if ($^O eq 'VMS' || $^O eq 'MSWin32' || $^O eq 'cygwin' || $^O =~ /freebsd/ || $^O eq 'midnightbsd' ||
     ($^O eq 'solaris' && $Config{osvers} eq '2.8') || $^O eq 'nto' ||
     ($^O eq 'darwin' && $osmajmin < 9) ||
    ((int($]*1000) & 1) == 0)
) {
    skip_all('various portability issues');
    exit 0;
}



my ($in, $out, $st, $sigst, $buf, $pipe_buf_size, $pipe_buf_err);

plan(tests => 10);


# make two handles that will always block

sub fresh_io {
    close $in if $in; close $out if $out;
    undef $in; undef $out; # use fresh handles each time
    pipe $in, $out;
    $sigst = "";
    $pipe_buf_err = "";

    # 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.
    $pipe_buf_size = eval {
        use Fcntl qw(F_GETPIPE_SZ);
        # When F_GETPIPE_SZ isn't implemented then fcntl() raises an exception:
        #   "Your vendor has not defined Fcntl macro F_GETPIPE_SZ ..."
        # When F_GETPIPE_SZ is implemented then errors are still possible
        # (EINVAL, EBADF, ...). These are not exceptions (i.e. these don't die)
        # but instead these set $! and make fcntl() return undef.
        fcntl($out, F_GETPIPE_SZ, 0) or die "$!\n";
    };
    if ($@ or not $pipe_buf_size) {
        my $err = $@;;
        chomp $err;
        $pipe_buf_size = 0xfffff;
        $pipe_buf_err = "fcntl F_GETPIPE_SZ failed" . ($err ? " ($err)" : "") .
                        ", falling back to $pipe_buf_size";
    };
    $pipe_buf_size++; # goal is to completely fill the buffer so write one
                      # byte more then the buffer size
}

$SIG{PIPE} = 'IGNORE';

# close during read

fresh_io;
$SIG{ALRM} = sub { $sigst = close($in) ? "ok" : "nok" };
alarm(1);
$st = read($in, $buf, 1);
alarm(0);
my $result = is($sigst, 'ok', 'read/close: sig handler close status');
$result &= ok(!$st, 'read/close: read status');
$result &= ok(!close($in), 'read/close: close status');
diag($pipe_buf_err) if (not $result and $pipe_buf_err);

# die during read

fresh_io;
$SIG{ALRM} = sub { die };
alarm(1);
$st = eval { read($in, $buf, 1) };
alarm(0);
$result = ok(!$st, 'read/die: read status');
$result &= ok(close($in), 'read/die: close status');
diag($pipe_buf_err) if (not $result and $pipe_buf_err);

SKIP: {
    skip "Tests hang on older versions of Darwin", 5
          if $^O eq 'darwin' && $osmajmin < 16;

    # close during print

    fresh_io;
    $SIG{ALRM} = sub { $sigst = close($out) ? "ok" : "nok" };
    $buf = "a" x $pipe_buf_size . "\n";
    select $out; $| = 1; select STDOUT;
    alarm(1);
    $st = print $out $buf;
    alarm(0);
    $result = is($sigst, 'nok', 'print/close: sig handler close status');
    $result &= ok(!$st, 'print/close: print status');
    $result &= ok(!close($out), 'print/close: close status');
    diag($pipe_buf_err) if (not $result and $pipe_buf_err);

    # die during print

    fresh_io;
    $SIG{ALRM} = sub { die };
    $buf = "a" x $pipe_buf_size . "\n";
    select $out; $| = 1; select STDOUT;
    alarm(1);
    $st = eval { print $out $buf };
    alarm(0);
    $result = ok(!$st, 'print/die: print status');
    # the close will hang since there's data to flush, so use alarm
    alarm(1);
    $result &= ok(!eval {close($out)}, 'print/die: close status');
    alarm(0);
    diag($pipe_buf_err) if (not $result and $pipe_buf_err);

    # 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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