no output from ice-9 `format' after `make-thread'

no output from ice-9 `format' after `make-thread'

[Eric Hanchrow]

Guile 1.6.0
Linux offby1 2.4.18 #1 Wed Aug 14 22:07:05 PDT 2002 i686 unknown

configured with `--prefix=/usr/local/guile1.6-threads --with-threads'

buildstamp = Thu Oct 31 06:05:53 PST 2002
LIBS =  -lqthreads -lpthread -lcrypt -lm 
libguileinterface = 15:0:3
guileversion = 1.6.0
pkgincludedir = /usr/local/guile1.6-threads/include/guile
pkglibdir = /usr/local/guile1.6-threads/lib/guile
pkgdatadir = /usr/local/guile1.6-threads/share/guile
includedir = /usr/local/guile1.6-threads/include
mandir = /usr/local/guile1.6-threads/man
infodir = /usr/local/guile1.6-threads/info
libdir = /usr/local/guile1.6-threads/lib
localstatedir = /usr/local/guile1.6-threads/var
sharedstatedir = /usr/local/guile1.6-threads/com
sysconfdir = /usr/local/guile1.6-threads/etc
datadir = /usr/local/guile1.6-threads/share
libexecdir = /usr/local/guile1.6-threads/libexec
sbindir = /usr/local/guile1.6-threads/sbin
bindir = /usr/local/guile1.6-threads/bin
exec_prefix = /usr/local/guile1.6-threads
prefix = /usr/local/guile1.6-threads
top_srcdir = top_srcdir_absolute@
srcdir = /usr/local/src/guile-1.6.0/libguile

unmodified source

no deviations from the standard procedure for installing Guile

here's a snippet that demonstrates the behavior I'm wondering about:

    (use-modules (ice-9 threads))
    (use-modules (ice-9 format))
    (for-each
     (lambda (sym)
       (make-thread
        (lambda ()
          (display (format #f "Hey you: ~A~%" sym))
          )))
     (list 'bob 'sam))

Invoke the snippet with `guile -s snippet.scm'.  Note the total lack
of output.

Compare this to what happens if you comment out `(use-modules (ice-9
format))', thus presumably bringing in a different `format' procedure:
you see output as I'd expect, namely

    Hey you: bob
    Hey you: sam

Also compare this to what happens if you eliminate the call to
`make-thread', like this:

    (use-modules (ice-9 format))
    (for-each
     (lambda (sym)
       (display (format #f "Hey you: ~A~%" sym)))
     (list 'bob 'sam))

This, too, produces the output shown above.

The bug, or at least my confusion, is that the first version produces
no output.

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Re: no output from ice-9 `format' after `make-thread'

[Marius Vollmer]

Eric Hanchrow <offby1@blarg.net> writes:

> Invoke the snippet with `guile -s snippet.scm'.  Note the total lack
> of output.

The process exits before it can produce any output.  "guile -s" exits
as soon as the main thread exits.  (The builtin simple-format is
probably fast enough to produce output anyway.)

Try this:

    (use-modules (ice-9 threads))
    (use-modules (ice-9 format))

    (define safe-format
      (let ((m (make-mutex)))
        (lambda args
          (with-mutex m
            (apply format args)))))

    (let ((ts (map (lambda (sym)
                     (make-thread
                      (lambda ()
                        (sleep (random 4))
                        (safe-format #t "Hey you: ~A~%" sym))))
                   (list 'bob 'sam 'huey 'luey 'duey))))
      (for-each join-thread ts))

It uses join-thread to wait for the threads to finish.

Note also that (ice-9 format) is not thread safe... (which I'm going
to fix soonish (when nothing preempts me)).

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Re: no output from ice-9 `format' after `make-thread'

[Neil Jerram]

>>>>> "Marius" == Marius Vollmer <mvo@zagadka.ping.de> writes:

    Marius> Note also that (ice-9 format) is not thread safe...

And also -- if it makes any difference -- not async safe.  I saw an
interesting bug the other day when GC happened somewhere in the middle
of (ice-9 format), and then:

GC -> after-gc-hook -> something that calls format again.

It wasn't happy about it.

    Marius> (which I'm going to fix soonish (when nothing preempts
    Marius> me)).

<groan>

        Neil



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Re: no output from ice-9 `format' after `make-thread'

[Marius Vollmer]

Neil Jerram <neil@ossau.uklinux.net> writes:

> >>>>> "Marius" == Marius Vollmer <mvo@zagadka.ping.de> writes:
> 
>     Marius> Note also that (ice-9 format) is not thread safe...
> 
> And also -- if it makes any difference -- not async safe.

Yeah, right, I didn't think about this.  When format is reimplemented
to nbe reentrant, then that will be fixed as well.  Currently, I have
only wrapped format in a monitor, which is not really good enough...

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