[NSString initialize] may have been in progress in another thread when fork() was called

[skaji]

cpm calls fork(2) internally.

If you use cpm on macOS, you may get errors like

❯ cpm install Foo::Bar
objc[80048]: +[NSString initialize] may have been in progress in another thread when fork() was called.
objc[80048]: +[NSString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
...
# FAIL

An easy workaround is to set environment variable OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES:

❯ env OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES cpm install Foo::Bar
# OK

Should this issue be fixed in perl itself?

See https://bugs.ruby-lang.org/issues/14009

[skaji]

minimal test case:

#!/usr/bin/env perl
use strict;
use warnings;

use Cwd;
use Socket 'inet_aton';

my $pid = fork // die;

if ($pid == 0) {
    inet_aton "invalid";
    exit;
}

wait;

❯ /usr/bin/perl test.pl
objc[34292]: +[NSString initialize] may have been in progress in another thread when fork() was called.
objc[34292]: +[NSString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.

[skaji]

Real world example:

# app.pl
use Mojolicious::Lite -signatures;

get '/' => sub ($c) {
  my $code = $c->app->ua->get("http://www.google.com")->result->code;
  $c->render(text => "google returns $code\n");
};

app->start;

❯ curl -fsSL https://cpanmin.us | /usr/bin/perl - -nq -Llocal Mojolicious
Successfully installed Mojolicious-9.36
1 distribution installed

❯ env PERL5LIB=$PWD/local/lib/perl5 /usr/bin/perl local/bin/hypnotoad -f app.pl
...

# access http://localhost:8080, then...

objc[35100]: +[NSString initialize] may have been in progress in another thread when fork() was called.
objc[35100]: +[NSString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
[2024-04-29 10:03:29.88360] [35097] [info] Worker 35100 stopped
[2024-04-29 10:03:29.88693] [35104] [info] Worker 35104 started