From: Ivan Maidanski <ivmai@mail.ru>
Date: Sat, 20 Jul 2013 11:21:37 +0000 (+0400)
Subject: Fix stackbottom/stack_end assignment in GC_call_with_gc_active
X-Git-Tag: gc7_4_0~38
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=14042f61bf4021abd27f9d630d487bdb203db5b5;p=gc

Fix stackbottom/stack_end assignment in GC_call_with_gc_active

* misc.c (GC_call_with_gc_active): Add GC_noop1 call between "fn" call
and "return" statement to discourage the compiler from treating the
function call as a tail one (thus ensuring "stackbottom" COOLER_THAN
any stack pointer value obtained inside "fn").
* pthread_support.c (GC_call_with_gc_active): Likewise.
* win32_threads.c (GC_call_with_gc_active): Likewise.
---

diff --git a/misc.c b/misc.c
index 366603c2..b6aa54e2 100644
--- a/misc.c
+++ b/misc.c
@@ -1859,7 +1859,10 @@ GC_API void * GC_CALL GC_call_with_gc_active(GC_fn_type fn,
 
     if (GC_blocked_sp == NULL) {
       /* We are not inside GC_do_blocking() - do nothing more.  */
-      return fn(client_data);
+      client_data = fn(client_data);
+      /* Prevent treating the above as a tail call.     */
+      GC_noop1((word)(&stacksect));
+      return client_data; /* result */
     }
 
     /* Setup new "stack section".       */
diff --git a/pthread_support.c b/pthread_support.c
index c129e63e..876c2a66 100644
--- a/pthread_support.c
+++ b/pthread_support.c
@@ -1267,7 +1267,10 @@ GC_API void * GC_CALL GC_call_with_gc_active(GC_fn_type fn,
     if (!me->thread_blocked) {
       /* We are not inside GC_do_blocking() - do nothing more.  */
       UNLOCK();
-      return fn(client_data);
+      client_data = fn(client_data);
+      /* Prevent treating the above as a tail call.     */
+      GC_noop1((word)(&stacksect));
+      return client_data; /* result */
     }
 
     /* Setup new "stack section".       */
diff --git a/win32_threads.c b/win32_threads.c
index c16946b7..84391783 100644
--- a/win32_threads.c
+++ b/win32_threads.c
@@ -896,7 +896,10 @@ GC_API void * GC_CALL GC_call_with_gc_active(GC_fn_type fn,
   if (me -> thread_blocked_sp == NULL) {
     /* We are not inside GC_do_blocking() - do nothing more.    */
     UNLOCK();
-    return fn(client_data);
+    client_data = fn(client_data);
+    /* Prevent treating the above as a tail call.       */
+    GC_noop1((word)(&stacksect));
+    return client_data; /* result */
   }
 
   /* Setup new "stack section". */