perl -d myprog autostarts - but only in one specific directory

ibm1620 has asked for the wisdom of the Perl Monks concerning the following question:

When I run the debugger on any program from one particular directory, it does not stop at the first executable line, but runs to completion as if I'd given the 'c' debugger command to continue.

The-Air:~/private/lewis_folder/client$ cat wjma.pl
#!/usr/bin/env perl
use warnings;
use strict;
print "HEY\n";
[download]

Here's my perl executable:

The-Air:~/private/lewis_folder/client$ which perl
/Users/chap/perl5/perlbrew/perls/perl-5.34.0/bin/perl
[download]

Demonstrating that the program works:

The-Air:~/private/lewis_folder/client$ ./wjma.pl
HEY
[download]

Demonstrating running debugger on program, from within the problem directory. Note that it automatically runs to completion.

The-Air:~/private/lewis_folder/client$ perl -d wjma.pl

Loading DB routines from perl5db.pl version 1.60
Editor support available.

Enter h or 'h h' for help, or 'man perldebug' for more help.

main::(wjma.pl:4):    print "HEY\n";
  DB<1> HEY
The-Air:~/private/lewis_folder/client$
[download]

Now I run the debugger on the same program while in a different directory. Note that it behaves correctly, stopping on the first statement.

The-Air:~$ /bin/pwd
/Users/chap
The-Air:~$ perl -d /Users/chap/private/lewis_folder/client/wjma.pl

Loading DB routines from perl5db.pl version 1.60
Editor support available.

Enter h or 'h h' for help, or 'man perldebug' for more help.

main::(/Users/chap/private/lewis_folder/client/wjma.pl:4):
4:    print "HEY\n";
  DB<1>
[download]

Now I run the debugger from the problem directory on the same program, located in a different directory. Note that again it runs to completion rather than stopping:

The-Air:~/private/lewis_folder/client$ perl -d /Users/chap/private/per
+l/wjma.pl

Loading DB routines from perl5db.pl version 1.60
Editor support available.

Enter h or 'h h' for help, or 'man perldebug' for more help.

main::(/Users/chap/private/perl/wjma.pl:4):
4:    print "HEY\n";
  DB<1> HEY
The-Air:~/private/lewis_folder/client$
[download]

So the problem occurs when I run perl -d from this one directory, which contains:

The-Air:~/private/lewis_folder/client$ ls -al
total 56
drwxrwxr-x  8 chap  staff    256 Jan 18 08:43 .
drwxrwxr-x  7 chap  staff    224 Apr  2  2020 ..
drwxrwxr-x  3 chap  staff     96 Jul 13  2013 con
lrwxrwxr-x  1 chap  staff     25 Nov 27  2015 dict -> /Users/chap/priv
+ate/text/
drwxrwxr-x  4 chap  staff    128 Sep 29  2010 dictorg
-rwxrwxr-x  1 chap  staff  15749 Jan 18 07:29 lewis-client
-rw-rw-r--  1 chap  staff   4880 Jan 17 19:56 lewis-client.config
-rwxr-xr-x  1 chap  staff     61 Jan 18 08:22 wjma.pl
The-Air:~/private/lewis_folder/client$
[download]

I'm scratching my head here. Any suggestions?

Comment on perl -d myprog autostarts - but only in one specific directory Select or Download Code

Replies are listed 'Best First'.
Re: perl -d myprog autostarts - but only in one specific directory by ikegami (Patriarch) on Jan 18, 2022 at 14:09 UTC
Could the debugger be reading from `con`? That's the equivalent of `/dev/tty` on Windows. Upd: I can't replicate your result exactly, but the existence of `con` is definitely a problem. In my test in Linux, it also wrote to `con`, which it then read, which caused more output, which ...	[reply] [d/l] [select]
Re^2: perl -d myprog autostarts - but only in one specific directory by bliako (Monsignor) on Jan 18, 2022 at 15:19 UTC
I can replicate on Linux. With an empty `con` dir in current dir, debugger does not break until program exits. If `./con` is a file, it writes to it and enters some kind of never-ending loop, as you say. `strace perl -d a.pl` shows this: `newfstatat(AT_FDCWD, "con", ..., ...)` Then, if `con` is found, it is opened with `openat(AT_FDCWD, "con", O_RDWR\|O_CREAT\|O_TRUNC\|O_CLOEXEC, 0666)` and it is writing to it. `perl a.pl` does not look for `con` The flag `AT_FDCWD` has the meaning of "relative to current dir", i.e. where you execute from and not where script is located. documentation mentions it: `If there is a TTY, we have to determine who it belongs to before we ca +n proceed. If this is a slave editor or graphical debugger (denoted b +y the first command-line switch being '-emacs'), we shift this off an +d set $rl to 0 (XXX ostensibly to do straight reads). We then determine what the console should be on various systems: Cygwin - We use stdin instead of a separate device. Windows or MSDOS - use con. AmigaOS - use CONSOLE:. VMS - use sys$command. Unix - use /dev/tty.` [download] Question is: why on Unix `con` has a role? And I find this in source of `perl5db.pl`: `elsif ( $^O eq 'dos' or -e "con" or $^O eq 'MSWin32' ) { $console = "con"; }` [download] `-e "con"` short-circuits the Unix check further down (if file or dir "con" exists in current dir): `if( -e '/dev/tty')`. Surely a bug AFAICS. bw, bliako	[reply] [d/l] [select]
Re^3: perl -d myprog autostarts - but only in one specific directory by choroba (Cardinal) on Jan 18, 2022 at 17:27 UTC
> Surely a bug AFAICS. AFAICF = as far as I can fix :-) `map{substr$_->[0],$_->[1]\|\|0,1}[\\|\|{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^ARGV,3]`	[reply] [d/l]
Re^4: perl -d myprog autostarts - but only in one specific directory by bliako (Monsignor) on Jan 18, 2022 at 19:34 UTC
Re^5: perl -d myprog autostarts - but only in one specific directory by pryrt (Abbot) on Jan 18, 2022 at 20:05 UTC
Some notes below your chosen depth have not been shown here
Re^2: perl -d myprog autostarts - but only in one specific directory by ibm1620 (Hermit) on Jan 18, 2022 at 22:43 UTC
Holy smokes. That was it. I deleted con/ and all is well. Incidentally, I don't see any evidence that anything was written into the directory, which just contained a small perl program whose purpose I no longer recall. Thank you all.	[reply]
Re^2: perl -d myprog autostarts - but only in one specific directory by bliako (Monsignor) on Jan 19, 2022 at 13:35 UTC
I did not know of that CON thingy and your mention let me to investigate it. ++	[reply]
Re: perl -d myprog autostarts - but only in one specific directory by Fletch (Bishop) on Jan 18, 2022 at 14:29 UTC
Was going to mention the possibility of a `.perldb` file but that's not showing up in your `ls` output. The other thing is maybe something is setting `PERLDB_OPTS` to contain "NonStop=1" in the misbehaving case (perhaps you're sourcing an extra startup file in the one shell you're not in the default case). The cake is a lie. The cake is a lie. The cake is a lie.	[reply] [d/l] [select]
Re^2: perl -d myprog autostarts - but only in one specific directory by LanX (Saint) on Jan 18, 2022 at 19:15 UTC
.perldb can be in home, and ENV could have special settings too.	[reply]
Re^3: perl -d myprog autostarts - but only in one specific directory by Fletch (Bishop) on Jan 18, 2022 at 19:38 UTC
Right but because things weren't misbehaving in other directories that was suggesting something wonky in a local startup config rather than the global user's. There's also packages (e.g. direnv) which setup environment variables specifically for different directories which could be in play. The `con` problem found earlier is most likely the culprit but things like this are worth keeping in mind. The cake is a lie. The cake is a lie. The cake is a lie.	[reply] [d/l]
Re^4: perl -d myprog autostarts - but only in one specific directory by LanX (Saint) on Jan 19, 2022 at 00:17 UTC
Re^5: perl -d myprog autostarts - but only in one specific directory by bliako (Monsignor) on Jan 19, 2022 at 13:33 UTC


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