Availability:C-language interface function
int PL_thread_attach_engine(const
PL_thread_attr_t *attr)Creates a new Prolog engine in the calling thread. If the calling thread
already has an engine the reference count of the engine is incremented.
The attr argument can be NULL to create a thread
with default attributes. Otherwise it is a pointer to a structure as
defined below. The structure must be fully initialized, including
hidden fields. For any field with value‘0’, the default is
used. The
cancel field may be filled with a pointer to a function
that is called when PL_cleanup()
terminates the running Prolog engines. The function is called with the
thread id (see PL_thread_self())
as argument and must return PL_THREAD_CANCEL_JOINED if the
thread was reclaimed successfully, PL_THREAD_CANCEL_MUST_JOIN
if the thread as cancelled, but must still be joined or
PL_THREAD_CANCEL_FAILED if the request cannot be honoured.
If this function is not present or returns PL_THREAD_CANCEL_FAILED
pthread_cancel() is used. The new thread inherits is properties
from Prolog's main thread. The flags field
defines the following flags:
- PL_THREAD_NO_DEBUG
- If this flag is present, the thread starts in normal no-debug status. By
default, the debug status is inherited from the main thread.
- PL_THREAD_NOT_DETACHED
- By default the new thread is created in detached mode. With
this flag it is created normally, allowing Prolog to join the
thread.
- PL_THREAD_CUR_STREAMS
- By default the
current_input and current_output
are set to user_input and user_output of the
main thread. Using this flag, these streams are copied from the main
thread. See also the inherited_from option of thread_create/3.
typedef struct
{ size_t stack_limit; /* Total stack limit (bytes) */
size_t table_space; /* Total tabling space limit (bytes) */
char * alias; /* alias name */
int (*cancel)(int thread); /* cancel function */
intptr_t flags; /* PL_THREAD_* flags */
size_t max_queue_size; /* Max size of associated queue */
char * thread_class; /* Class property of the thread */
} PL_thread_attr_t;
The structure may be destroyed after PL_thread_attach_engine()
has returned. On success it returns the Prolog identifier for the thread
(as returned by PL_thread_self()).
If an error occurs, -1 is returned. If this Prolog is not compiled for
multithreading, -2 is returned.
