Commit 17b084af authored by Ben Gamari's avatar Ben Gamari 🐢
Browse files

rts: Reset STATIC_LINK field of reverted CAFs

When we revert a CAF we must reset the STATIC_LINK field lest the GC
might ignore the CAF (e.g. as it carries the STATIC_FLAG_LIST flag) and
will consequently overlook references to object code that we are trying
to unload. This would result in the reachable object code being
unloaded. See Note [CAF lists] and Note [STATIC_LINK fields].

This fixes #16842.

Idea-due-to: Phuong Trinh <>
(cherry picked from commit 2a960c3a)
parent 4d8a7206
...@@ -114,16 +114,21 @@ isAlive(StgClosure *p) ...@@ -114,16 +114,21 @@ isAlive(StgClosure *p)
void void
revertCAFs( void ) revertCAFs( void )
{ {
StgIndStatic *c; StgIndStatic *c = revertible_caf_list;
for (c = revertible_caf_list; while (c != (StgIndStatic *) END_OF_CAF_LIST) {
c != (StgIndStatic *)END_OF_CAF_LIST;
c = (StgIndStatic *)c->static_link)
c = (StgIndStatic *)UNTAG_STATIC_LIST_PTR(c); c = (StgIndStatic *)UNTAG_STATIC_LIST_PTR(c);
StgIndStatic *next = (StgIndStatic *) c->static_link;
SET_INFO((StgClosure *)c, c->saved_info); SET_INFO((StgClosure *)c, c->saved_info);
c->saved_info = NULL; c->saved_info = NULL;
// could, but not necessary: c->static_link = NULL; // We must reset static_link lest the major GC finds that
// static_flag==3 and will consequently ignore references
// into code that we are trying to unload. This would result
// in reachable object code being unloaded prematurely.
// See #16842.
c->static_link = NULL;
c = next;
} }
revertible_caf_list = (StgIndStatic*)END_OF_CAF_LIST; revertible_caf_list = (StgIndStatic*)END_OF_CAF_LIST;
} }
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment