Eval procedure doesn't work in the newly created thread.

[niyarin]

When I execute the eval procedure in the newly created thread, the value is not returned.

It worked in ver0.99. It also worked on the REPL.
I'm sorry if I'm wrong.

(import (scheme base) (scheme eval)  (srfi 18))

(let ((thread (make-thread
                (lambda () (eval '(write (cons 1 2))
                                 (environment '(scheme base) '(scheme write)))))))
  (thread-start! thread)
  (thread-join! thread))

[shirok]

Wow. Good catch.
It is actually not eval, but an unexpected side effect of changing port structure, though it can be revealed only when number of conditions are met.

• In 0.9.10 I changed Scm_Port to keep the port name (source file name if it's a file port) in the port attributes, rather than in a separate slot. Port attributes are a general mechanism to associate arbitrary key-value pairs to each ports, and it seemed a good idea to treat port name as one of the attributes.
• Port attributes can be modified at any time, so its access is mutexed by the lock in each port.
• That lock is also used while one thread accessing a port.
• Each thread keeps a parameter current-load-port, which is set during the thread is loading code from a port.
• When a thread is created, it inherits parameter values from the creator thread.
• Hence, if a thread is created during loading a script, the created thread shares the same port as current-load-port.
• Eval in the child thread calls the compiler.
• The compiler tries to take the name of the current loading port as the source code information.
• However, the port is locked by the parent thread, since it is still loading the script from it.
• Deadlock.

I'd say it's a bug, for attribute access needs only be locked during attribute access and doesn't need to coincide with the port access. But this particular situation only occurs when you create a new thread and calls eval while the main thread is still loading from the script. That's why it hasn't been unnoticed.

[shirok]

I'll fix this by the next release, but if this gets in your way, one workaround is not to do everything during loading the script file; for example, if you execute the main program via the main procedure, eval is called after the script is loaded so it won't deadlock.

(import (scheme base) (scheme eval) (srfi 18))

(define (main args)
  (let ((thread (make-thread
                 (lambda ()
                   (eval '(write (cons 1 2))
                         (environment '(scheme base) '(scheme write)))))))
    (thread-start! thread)
    (thread-join! thread))
  0)

Note that srfi-22 (the feature that main is called) isn't enabled for R7RS scripts, so you need a special command-line option:

gosh -mr7rs.user script.scm

[shirok]

Fixed in the HEAD.