Re: [commit: ghc] master: Fix linked list manipulation code (buggy on consecutive deletion) (e3938f3)

14 Apr 2014

Thanks Edward.  Austin, can you cherry-pick this for 7.8.3 please?

Cheers,
Simon

On 13/04/2014 07:37, git@git.haskell.org wrote:
...
Repository : ssh://git@git.haskell.org/ghc
On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/e3938f3adac0093b23694fd347774244ce...
...
---------------------------------------------------------------
commit e3938f3adac0093b23694fd347774244ce121478
Author: Edward Z. Yang 
Date:   Sat Apr 12 23:02:13 2014 -0700
Fix linked list manipulation code (buggy on consecutive deletion)
Signed-off-by: Edward Z. Yang 
...
---------------------------------------------------------------
e3938f3adac0093b23694fd347774244ce121478
  rts/CheckUnload.c |    3 ++-
  rts/Linker.c      |    6 ++++--
  2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/rts/CheckUnload.c b/rts/CheckUnload.c
index f1f454c..98f184b 100644
--- a/rts/CheckUnload.c
+++ b/rts/CheckUnload.c
@@ -298,7 +298,7 @@ void checkUnload (StgClosure *static_objects)
    // marked as unreferenced can be physically unloaded, because we
    // have no references to it.
    prev = NULL;
-  for (oc = unloaded_objects; oc; prev = oc, oc = next) {
+  for (oc = unloaded_objects; oc; oc = next) {
        next = oc->next;
        if (oc->referenced == 0) {
            if (prev == NULL) {
@@ -312,6 +312,7 @@ void checkUnload (StgClosure *static_objects)
        } else {
            IF_DEBUG(linker, debugBelch("Object file still in use: %"
                                        PATH_FMT "\n", oc->fileName));
+          prev = oc;
        }
    }
diff --git a/rts/Linker.c b/rts/Linker.c
index af26d74..ab235e9 100644
--- a/rts/Linker.c
+++ b/rts/Linker.c
@@ -3016,8 +3016,8 @@ unloadObj( pathchar *path )
      IF_DEBUG(linker, debugBelch("unloadObj: %" PATH_FMT "\n", path));
prev = NULL;
-    for (oc = objects; oc; prev = oc, oc = next) {
-        next = oc->next;
+    for (oc = objects; oc; oc = next) {
+        next = oc->next; // oc might be freed
if (!pathcmp(oc->fileName,path)) {
@@ -3075,6 +3075,8 @@ unloadObj( pathchar *path )
              /* This could be a member of an archive so continue
               * unloading other members. */
              unloadedAnyObj = HS_BOOL_TRUE;
+        } else {
+            prev = oc;
          }
      }
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Simon Marlow

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