[MASSMAIL]In MacOS, psql reacts on SIGINT in a strange fashion (Linux is fine)

Preamble: this happens in MacOS only (in built-in Terminal and in iTerm2 at least). In Linux, everything is as expected.

I tried to find a place in psql source code where it fans out SIGINT to its parent pids upon receiving. But I did not find any. There is also no shell involved in all these (see logs below).

Any ideas, who is doing this on MacOS? Who is sending 2 extra SIGINTs to 2 parents when a SIGINT is delivered to psql?

I also tried to use any other signal-trapping program instead of psql (like vim or an artificial Perl script which ignores signals) and did not observe the same behavior. It looks like something very specific to psql.

Steps to reproduce:

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Terminal 1:


% cat /tmp/my1.pl
#!/usr/bin/perl -w
if (fork()) {
  $SIG{INT} = sub { print("int in my1\n") };
  while (1) { wait() and exit(1); }
} else {
  exec("/tmp/my2.pl");
}

% cat /tmp/my2.pl
#!/usr/bin/perl -w
if (fork()) {
  $SIG{INT} = sub { print("int in my2\n") };
  while (1) { wait() and exit(1); }
} else {
  exec("psql");
}

# PostgreSQL server is running in Docker, localhost remapped port 15432
% PGHOST=127.0.0.1 PGPORT=15432 PGUSER=postgres PGPASSWORD=postgres PGDATABASE=postgres /tmp/my1.pl
psql (16.0, server 13.5 (Debian 13.5-1.pgdg110+1))
Type "help" for help.
postgres=#


Terminal 2:

% pstree | grep -E "bash |yarn|psql|vim|sleep|lldb|my.pl|perl" | grep dmitry | grep -v grep

 
 |   |   \-+= 24550 dmitry /usr/bin/perl -w /tmp/my1.pl
 |   |     \-+- 24551 dmitry /usr/bin/perl -w /tmp/my2.pl
 |   |       \--- 24552 dmitry psql

% pgrep psql
24552
% kill -SIGINT 24552


And I see this in Terminal 1:

postgres=#
int in my2
int in my1

postgres=#

===========================