Hi,
I am finding that things defined in one thread are not always
visible in another. This seems to be due to some threads
having a different current-module than others. I think this is a bug.
The example code below shows the issue. Help, comments
appreciated.
--linas
/**
* Guile threading bug/unexpected behaviour.
*
* Two posix threads are created. The first thread runs, and defines
* something. The second thread tries to access the thing defined by
* the first. But, due to some "unexpected" threading behaviour, the
* things defined in the first thread are not visible to the first.
* I'm pretty convinced this is a bug, and am hunting it down now.
*
* The printed output of this program, for me, under guile1.8.5, is
*
* HEllo, thread one is running
* Goodbye, thread one is exiting
* HEllo, thread two is running
* ERROR: Unbound variable: x
* Goodbye, thread two is exiting
* Main is exiting
*
* To get a better idea of what's going on, it seems to have something
* to do with the current module. By turning on print debugging, the
* output, for me, becomes:
*
* HEllo, thread one is running
* thread one had output:
* the root module is #<module (guile) f73f9e80>
* the current module is #<directory (guile-user) f73fc600>
*
* Goodbye, thread one is exiting
* HEllo, thread two is running
* thread two had output:
* the root module is #<module (guile) f73f9e80>
* the current module is #<module (guile) f73f9e80>
*
* ERROR: Unbound variable: x
* Goodbye, thread two is exiting
* Main is exiting
*/
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <libguile.h>
void prtdbg(const char * id)
{
// #define SHOW_STUFF 1
#ifdef SHOW_STUFF
SCM outport = scm_open_output_string();
scm_set_current_output_port(outport);
scm_c_eval_string ("(display \"the root module is \")\n");
scm_c_eval_string ("(display the-root-module)\n");
scm_c_eval_string ("(newline)\n");
scm_c_eval_string ("(display \"the current module is \")\n");
scm_c_eval_string ("(display (current-module))\n");
scm_c_eval_string ("(newline)\n");
SCM out = scm_get_output_string(outport);
char * str = scm_to_locale_string(out);
// scm_truncate_file(outport, scm_from_uint16(0));
printf("%s had output:\n%s\n", id, str);
#endif
}
void * scm_one (void *p)
{
prtdbg("thread one");
scm_c_eval_string ("(define x \"asddf\")\n");
}
void * scm_two (void *p)
{
prtdbg("thread two");
scm_c_eval_string ("(display x)\n");
}
static void * thread_one (void * arg)
{
printf("HEllo, thread one is running\n");
scm_with_guile(scm_one, NULL);
printf("Goodbye, thread one is exiting\n");
return NULL;
}
static void * thread_two (void * arg)
{
printf("HEllo, thread two is running\n");
scm_with_guile(scm_two, NULL);
printf("Goodbye, thread two is exiting\n");
return NULL;
}
main()
{
int rc;
pthread_attr_t attr;
pthread_t t1, t2;
pthread_attr_init(&attr);
rc = pthread_create(&t1, &attr, thread_one, NULL);
if(rc)
{
fprintf(stderr, "Fatal error: can't create thread one\n");
exit(1);
}
sleep(1);
rc = pthread_create(&t2, &attr, thread_two, NULL);
if(rc)
{
fprintf(stderr, "Fatal error: can't create thread two\n");
exit(1);
}
sleep(5);
printf("Main is exiting\n");
}
