[commit: ghc] ghc-7.8: Fix linked list manipulation code (buggy on consecutive deletion) (f405460)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : ghc-7.8
Link       : http://ghc.haskell.org/trac/ghc/changeset/f40546053913a2cffe158605337e35a319fe2804/ghc

>---------------------------------------------------------------

commit f40546053913a2cffe158605337e35a319fe2804
Author: Edward Z. Yang <ezyang at cs.stanford.edu>
Date:   Sat Apr 12 23:02:13 2014 -0700

    Fix linked list manipulation code (buggy on consecutive deletion)
    
    Signed-off-by: Edward Z. Yang <ezyang at cs.stanford.edu>
    (cherry picked from commit e3938f3adac0093b23694fd347774244ce121478)


>---------------------------------------------------------------

f40546053913a2cffe158605337e35a319fe2804
 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 8692dea..b381fca 100644
--- a/rts/CheckUnload.c
+++ b/rts/CheckUnload.c
@@ -290,7 +290,7 @@ 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) {
@@ -304,6 +304,7 @@ 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 814f930..c577cce 100644
--- a/rts/Linker.c
+++ b/rts/Linker.c
@@ -2928,8 +2928,8 @@ 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)) {
 
@@ -2987,6 +2987,8 @@ unloadObj( pathchar *path )
             /* This could be a member of an archive so continue
              * unloading other members. */
             unloadedAnyObj = HS_BOOL_TRUE;
+        } else {
+            prev = oc;
         }
     }