From 4ee871c7812c84631e2e8127302f76df190ffe18 Mon Sep 17 00:00:00 2001
From: "Brian J. Cardiff" <bcardiff@gmail.com>
Date: Mon, 7 Jan 2019 17:41:35 -0300
Subject: [PATCH] Added functions to get and set the stackbottom of each thread

---
 include/gc.h      | 10 ++++++++++
 pthread_support.c | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/include/gc.h b/include/gc.h
index d6fec2b5..1a80154d 100644
--- a/include/gc.h
+++ b/include/gc.h
@@ -362,6 +362,16 @@ GC_API GC_ATTR_DEPRECATED char *GC_stackbottom;
                                 /* GC_call_with_gc_active() and         */
                                 /* GC_register_my_thread() instead.     */
 
+/* Sets the cool end of user stack in the specified thread.              */
+/* MUST be called with the GC disabled.                                 */
+GC_API void GC_CALL GC_set_stackbottom(void * thread, char * stackbottom);
+
+/* Returns the cool end of user stack of the current thread/coroutine.  */
+/* When a thread starts it will be computed upon creation.              */
+/* If GC_switch_to_coroutine() is called, the returned value will match */
+/* the specified value in that function.                                 */
+GC_API char * GC_CALL GC_get_stackbottom();
+
 GC_API GC_ATTR_DEPRECATED int GC_dont_precollect;
                                 /* Do not collect as part of GC         */
                                 /* initialization.  Should be set only  */
diff --git a/pthread_support.c b/pthread_support.c
index 78e5d35a..e99c4b81 100644
--- a/pthread_support.c
+++ b/pthread_support.c
@@ -1369,6 +1369,44 @@ GC_INNER void GC_do_blocking_inner(ptr_t data, void * context GC_ATTR_UNUSED)
     UNLOCK();
 }
 
+/* Sets the cool end of user stack in the specified thread.              */
+/* MUST be called with the GC disabled.                                 */
+GC_API void GC_CALL GC_set_stackbottom(void * thread, char * stackbottom)
+{
+    GC_thread me;
+
+    me = GC_lookup_thread((pthread_t) thread);
+
+    if ((me -> flags & MAIN_THREAD) == 0) {
+        me -> stack_end = stackbottom;
+    } else {
+        GC_stackbottom = stackbottom;
+    }
+}
+
+/* Returns the cool end of user stack of the current thread/corutine.   */
+/* When a thread starts it will be computed upon creation.              */
+/* If GC_switch_to_coroutine() is called, the returned value will match */
+/* the specified value in that function.                                 */
+GC_API char * GC_CALL GC_get_stackbottom()
+{
+    pthread_t self = pthread_self();
+    GC_thread me;
+    char * ret;
+
+    LOCK();
+    me = GC_lookup_thread(self);
+
+    if ((me -> flags & MAIN_THREAD) == 0) {
+        ret = me -> stack_end;
+    } else {
+        ret = GC_stackbottom;
+    }
+    UNLOCK();
+
+    return ret;
+}
+
 /* 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   */