Mps: bug fix revealed by mpsicv

Copied from Perforce
 Change: 64245
 ServerID: perforce.ravenbrook.com

2 files changed, 4 insertions, 2 deletions

diff --git a/mps/code/global.c b/mps/code/global.c
index 8876811d3ee..98299dbbcc6 100644
--- a/mps/code/global.c
+++ b/mps/code/global.c
@@ -144,7 +144,7 @@ Bool GlobalsCheck(Globals arenaGlobals)
   CHECKL(RingCheck(&arenaGlobals->rootRing));
   CHECKL(RingCheck(&arenaGlobals->rememberedSummaryRing));
   CHECKL(arenaGlobals->rememberedSummaryIndex < RememberedSummaryBLOCK);
-  /* RingIsSingle imples index == 0 */
+  /* <code/global.c#remembered.summary> RingIsSingle imples index == 0 */
   CHECKL(!RingIsSingle(&arenaGlobals->rememberedSummaryRing) ||
     arenaGlobals->rememberedSummaryIndex == 0);
   CHECKL(RingCheck(&arena->formatRing));
diff --git a/mps/code/trace.c b/mps/code/trace.c
index bfc21dd9736..07723fc0bf5 100644
--- a/mps/code/trace.c
+++ b/mps/code/trace.c
@@ -1824,6 +1824,9 @@ void arenaForgetProtection(Globals globals)
   Arena arena;
 
   arena = GlobalsArena(globals);
+  /* Setting this early means that we preserve the invariant
+     <code/global.c#remembered.summary> */
+  globals->rememberedSummaryIndex = 0;
   RING_FOR(node, GlobalsRememberedSummaryRing(globals), next) {
     RememberedSummaryBlock block =
       RING_ELT(RememberedSummaryBlock, globalRing, node);
@@ -1831,7 +1834,6 @@ void arenaForgetProtection(Globals globals)
     RingRemove(node);
     ControlFree(arena, block, sizeof *block);
   }
-  globals->rememberedSummaryIndex = 0;
   return;
 }