Add API functions to get and set the stack bottom of each thread

Issue #277 (bdwgc).

This API is useful to support coroutines.

* include/gc.h (GC_get_my_stackbottom, GC_set_stackbottom): New API
function declaration.
* misc.c [!THREADS] (GC_set_stackbottom, GC_get_my_stackbottom): New
function definition.
* pthread_support.c [GC_PTHREADS && !GC_WIN32_THREADS]
(GC_set_stackbottom, GC_get_my_stackbottom): Likewise.
* win32_threads.c [GC_WIN32_THREADS] (GC_set_stackbottom,
GC_get_my_stackbottom): Likewise.
* tests/test.c (struct thr_hndl_sb_s): Define.
* tests/test.c (set_stackbottom): New function (which calls
GC_set_stackbottom).
* tests/test.c (run_one_test): Define thr_hndl_sb local variable;
call GC_get_my_stackbottom() and set_stackbottom().
* win32_threads.c [GC_WIN32_THREADS && I386] (struct GC_Thread_Rep):
Add initial_stack_base field.
* win32_threads.c [GC_WIN32_THREADS && I386] (GC_record_stack_base,
GC_call_with_gc_active): Set initial_stack_base field.
* win32_threads.c [GC_WIN32_THREADS && I386] (GC_push_stack_for): Handle
the case when GetThreadContext() might return stale register values,
thread stack_base != initial_stack_base but the stack is not inside
the TIB stack (use context.Esp but call WARN); add TODO.

1 files changed, 56 insertions, 0 deletions

diff --git a/pthread_support.c b/pthread_support.c
index 6c138c1c..0b2af4ac 100644
--- a/pthread_support.c
+++ b/pthread_support.c
@@ -1403,6 +1403,62 @@ GC_INNER void GC_do_blocking_inner(ptr_t data, void * context GC_ATTR_UNUSED)
     UNLOCK();
 }
 
+GC_API void GC_CALL GC_set_stackbottom(void *gc_thread_handle,
+                                       const struct GC_stack_base *sb)
+{
+    GC_thread t = (GC_thread)gc_thread_handle;
+
+    GC_ASSERT(sb -> mem_base != NULL);
+    if (!EXPECT(GC_is_initialized, TRUE)) {
+        GC_ASSERT(NULL == t);
+    } else {
+        GC_ASSERT(I_HOLD_LOCK());
+        if (NULL == t) /* current thread? */
+            t = GC_lookup_thread(pthread_self());
+        GC_ASSERT((t -> flags & FINISHED) == 0);
+        GC_ASSERT(!(t -> thread_blocked)
+                  && NULL == t -> traced_stack_sect); /* for now */
+
+        if ((t -> flags & MAIN_THREAD) == 0) {
+            t -> stack_end = (ptr_t)sb->mem_base;
+#           ifdef IA64
+                t -> backing_store_end = (ptr_t)sb->reg_base;
+#           endif
+            return;
+        }
+        /* Otherwise alter the stack bottom of the primordial thread.   */
+    }
+
+    GC_stackbottom = (char*)sb->mem_base;
+#   ifdef IA64
+        GC_register_stackbottom = (ptr_t)sb->reg_base;
+#   endif
+}
+
+GC_API void * GC_CALL GC_get_my_stackbottom(struct GC_stack_base *sb)
+{
+    pthread_t self = pthread_self();
+    GC_thread me;
+    DCL_LOCK_STATE;
+
+    LOCK();
+    me = GC_lookup_thread(self);
+    /* The thread is assumed to be registered.  */
+    if ((me -> flags & MAIN_THREAD) == 0) {
+        sb -> mem_base = me -> stack_end;
+#       ifdef IA64
+            sb -> reg_base = me -> backing_store_end;
+#       endif
+    } else {
+        sb -> mem_base = GC_stackbottom;
+#       ifdef IA64
+            sb -> reg_base = GC_register_stackbottom;
+#       endif
+    }
+    UNLOCK();
+    return (void *)me; /* gc_thread_handle */
+}
+
 /* GC_call_with_gc_active() has the opposite to GC_do_blocking()        */
 /* functionality.  It might be called from a user function invoked by   */
 /* GC_do_blocking() to temporarily back allow calling any GC function   */