[Notion-devel] Problems regarding intercepting SIGCHLD in NetBSD

[Silas S. <si...@gm...>]

Hi all!

I use ion3 and now notion for about 4 years, first in GNU/Linux and now
in NetBSD.

In NetBSD, I started to customize my statusbar with statusd scripts,
adapting some from contrib and making some of them myself.  But, I had
to make some ugly changes on them.

In order to make external commands work, I had to add os.execute("sleep
1") just after io.popen().  Yes, it worked and since I didn't have time
to investigate the problem, I worked that way a long time.

Now I decided to investigate the problem further.  I made a small
statusd_test.lua script:

    local test_timer = statusd.create_timer()
    local function update_test()
        local f = io.popen('echo x', 'r')
        os.execute("sleep 1")
        local value = f:read('*all')
        statusd.inform("test", value)
        test_timer:set(1000, update_test)
    end

    update_test()

Without os.execute("sleep 1"), I receive:

    test: x

    .
    test: (null)
    .
    test: (null)
    ...

But, with os.execute("sleep 1"), it works fine.

I soon realized that time events were generated by SIGALRM.  So there
could be anything related with signals.  So, my investigations confirm
that a minor change is necessary to make it work.  Just comment line 543
of libmainloop/signal.c:

    sigaction(SIGCHLD, &sa, NULL);

And it works like a charm, but I don't know if it breaks other things.

I'm not a C programmer expert.  So I'd like to ask you if you know why
it could be happening.  If it works under GNU/Linux, it is probably
something regarding implementation of signals in NetBSD.

Do you have any idea?

Why SIGCHLD is being intercepted?

Thanks in advance.

-- 
Silas Silva