Hi Rubén
On 03/06/2024 21:38, Rubén Justo wrote:
In 18d8c26930 (test_terminal: redirect child process' stdin to a pty,
2015-08-04), t/test-terminal.perl learned to connect the child process'
stdin to a pty. It works well for what was intended: satisfying an
`isatty(STDIN_FILENO)` check.
However, the fork introduced, that copies the stdin to the child
process, does not always manage to send all the information.
I think the problem maybe to do with the use of File::Copy, not with the
fork. The man page for the copy function says
Note that passing in files as handles instead of names may
lead to loss of information on some operating systems; it is
recommended that you use file names whenever possible.
Rather than adding a new flag to work around a bug in our script it
might be better to try and fix the bug by using a loop that reads blocks
of data from the source and writes them to the destination instead of
calling copy.
Best Wishes
Phillip
To illustrate this behaviour, we can use a function like this:
f ()
{
dd if=/dev/zero bs=1 count=10000 status=none |
t/test-terminal.perl cat - 2>/dev/null |
wc -c;
}
We do not obtain the expected results when executing this function
100 times:
$ for i in $(seq 100); do f; done | sort | uniq -c
36 0
4 1
53 4095
7 4159
If we do the same with a version that does not redirect stdin, a version
prior to 18d8c26930, the expected result is obtained:
$ git checkout 18d8c26930~1
$ for i in $(seq 100); do f; done | sort | uniq -c
100 10000
In a subsequent commit, a new test is going to rely on test-terminate,
and it does not require stdin to be connected to a terminal, but all
piped data needs to be successfully transmitted to the child process.
To make this possible, add a new parameter "--no-stdin-pty" to allow
disabling the stdin redirection though a pty.
Signed-off-by: Rubén Justo <rjusto@xxxxxxxxx>
---
t/test-terminal.perl | 32 ++++++++++++++++++--------------
1 file changed, 18 insertions(+), 14 deletions(-)
diff --git a/t/test-terminal.perl b/t/test-terminal.perl
index 3810e9bb43..85edc9e8b9 100755
--- a/t/test-terminal.perl
+++ b/t/test-terminal.perl
@@ -12,10 +12,10 @@ sub start_child {
if (not defined $pid) {
die "fork failed: $!"
} elsif ($pid == 0) {
- open STDIN, "<&", $in;
+ open STDIN, "<&", $in if $in;
open STDOUT, ">&", $out;
open STDERR, ">&", $err;
- close $in;
+ close $in if $in;
close $out;
exec(@$argv) or die "cannot exec '$argv->[0]': $!"
}
@@ -78,28 +78,32 @@ sub copy_stdio {
}
if ($#ARGV < 1) {
- die "usage: test-terminal program args";
+ die "usage: test-terminal [--no-stdin-pty] program args";
}
+my $no_stdin_pty = $ARGV[0] eq '--no-stdin-pty';
+shift @ARGV if $no_stdin_pty;
$ENV{TERM} = 'vt100';
-my $parent_in = new IO::Pty;
+my $parent_in = $no_stdin_pty ? undef : IO::Pty->new;
my $parent_out = new IO::Pty;
my $parent_err = new IO::Pty;
-$parent_in->set_raw();
+$parent_in->set_raw() if $parent_in;
$parent_out->set_raw();
$parent_err->set_raw();
-$parent_in->slave->set_raw();
+$parent_in->slave->set_raw() if $parent_in;
$parent_out->slave->set_raw();
$parent_err->slave->set_raw();
-my $pid = start_child(\@ARGV, $parent_in->slave, $parent_out->slave, $parent_err->slave);
-close $parent_in->slave;
+my $pid = start_child(\@ARGV,$parent_in ? $parent_in->slave : undef, $parent_out->slave, $parent_err->slave);
+close $parent_in->slave if $parent_in;
close $parent_out->slave;
close $parent_err->slave;
-my $in_pid = copy_stdin($parent_in);
+my $in_pid = $no_stdin_pty ? 0 : copy_stdin($parent_in);
copy_stdio($parent_out, $parent_err);
my $ret = finish_child($pid);
-# If the child process terminates before our copy_stdin() process is able to
-# write all of its data to $parent_in, the copy_stdin() process could stall.
-# Send SIGTERM to it to ensure it terminates.
-kill 'TERM', $in_pid;
-finish_child($in_pid);
+if ($in_pid) {
+ # If the child process terminates before our copy_stdin() process is able to
+ # write all of its data to $parent_in, the copy_stdin() process could stall.
+ # Send SIGTERM to it to ensure it terminates.
+ kill 'TERM', $in_pid;
+ finish_child($in_pid);
+}
exit($ret);
