Re: libguile thread safety

[ludo@gnu.org (Ludovic Courtès)]

Hi,

Chris Vine <chris@cvine.freeserve.co.uk> skribis:

> I am having problems using libguile in a multi-threaded environment,
> which boils down to the following small test case, which fails with a
> segmentation fault with guile-2.0.9:
>
> #include <libguile.h>
> #include <pthread.h>
>
> void *guile_wrapper (void *data) {
>   scm_c_eval_string ("(display \"Hello\n\")");
>   return NULL;
> }
>
> void *thread_func (void *data) {
>   scm_with_guile (&guile_wrapper, NULL);
>   return NULL;
> }
>
> int main () {
>   pthread_t thread1;
>   pthread_t thread2;
>
>   pthread_create (&thread1, NULL, thread_func, NULL);
>   pthread_create (&thread2, NULL, thread_func, NULL);
>
>   pthread_join (thread1, NULL);
>   pthread_join (thread2, NULL);
>   return 0;
> }

This should work (but see below.)  In fact, this is what
test-pthread-create-secondary.c tests (in Guile’s test suite.)

It may fail if libgc was built without pthread support, or if it’s an
old version (older than 7.2alpha6).  Could you check that?

However, ports themselves are not thread-safe in 2.0, and the code above
has several threads writing to the current output port, which is a
problem.  When an application has several threads using the same port,
it must do its own locking currently.

Thanks,
Ludo’.