From d02a8f277e7b1476bc2b28af7ae724d5a3b34ffe Mon Sep 17 00:00:00 2001
From: Gareth Rees <gdr@ravenbrook.com>
Date: Thu, 30 Mar 2017 11:37:41 +0100
Subject: [PATCH] Check that segment classes override sets of related methods.

Add missing finish functions amcSegFinish, mrgLinkSegFinish, mrgRefSegFinish, sncSegFinish.
Check all class constructor results.

Copied from Perforce
 Change: 193055
 ServerID: perforce.ravenbrook.com
---
 mps/code/arena.c    |  2 ++
 mps/code/arenacl.c  |  1 +
 mps/code/arenavm.c  |  1 +
 mps/code/buffer.c   |  4 ++++
 mps/code/cbs.c      |  3 +++
 mps/code/failover.c |  1 +
 mps/code/freelist.c |  1 +
 mps/code/land.c     |  2 ++
 mps/code/pool.c     |  7 -------
 mps/code/poolabs.c  |  5 +++++
 mps/code/poolamc.c  | 19 +++++++++++++++++++
 mps/code/poolams.c  |  1 +
 mps/code/poolawl.c  |  2 ++
 mps/code/poollo.c   |  2 ++
 mps/code/poolmfs.c  |  1 +
 mps/code/poolmrg.c  | 34 +++++++++++++++++++++++++++++++++-
 mps/code/poolmv.c   |  2 ++
 mps/code/poolmv2.c  |  1 +
 mps/code/poolmvff.c |  2 ++
 mps/code/poolsnc.c  | 18 ++++++++++++++++++
 mps/code/protocol.c |  2 ++
 mps/code/seg.c      | 11 +++++++++++
 mps/code/segsmss.c  |  1 +
 23 files changed, 115 insertions(+), 8 deletions(-)

diff --git a/mps/code/arena.c b/mps/code/arena.c
index 6d56b8bf62f..92ffcffa347 100644
--- a/mps/code/arena.c
+++ b/mps/code/arena.c
@@ -107,6 +107,7 @@ static void ArenaNoDestroy(Arena arena)
 DEFINE_CLASS(Inst, ArenaClass, klass)
 {
   INHERIT_CLASS(klass, ArenaClass, InstClass);
+  AVERT(InstClass, klass);
 }
 
 
@@ -132,6 +133,7 @@ DEFINE_CLASS(Arena, AbstractArena, klass)
   klass->pagesMarkAllocated = ArenaNoPagesMarkAllocated;
   klass->chunkPageMapped = ArenaNoChunkPageMapped;
   klass->sig = ArenaClassSig;
+  AVERT(ArenaClass, klass);
 }
 
 
diff --git a/mps/code/arenacl.c b/mps/code/arenacl.c
index 757b4c7326c..e2a0da37095 100644
--- a/mps/code/arenacl.c
+++ b/mps/code/arenacl.c
@@ -458,6 +458,7 @@ DEFINE_CLASS(Arena, ClientArena, klass)
   klass->chunkInit = ClientChunkInit;
   klass->chunkFinish = ClientChunkFinish;
   klass->chunkPageMapped = ClientChunkPageMapped;
+  AVERT(ArenaClass, klass);
 }
 
 
diff --git a/mps/code/arenavm.c b/mps/code/arenavm.c
index 78e2a67cbf4..4f7dbe2963d 100644
--- a/mps/code/arenavm.c
+++ b/mps/code/arenavm.c
@@ -1219,6 +1219,7 @@ DEFINE_CLASS(Arena, VMArena, klass)
   klass->compact = VMCompact;
   klass->pagesMarkAllocated = VMPagesMarkAllocated;
   klass->chunkPageMapped = VMChunkPageMapped;
+  AVERT(ArenaClass, klass);
 }
 
 
diff --git a/mps/code/buffer.c b/mps/code/buffer.c
index 1595421c171..908bb532b24 100644
--- a/mps/code/buffer.c
+++ b/mps/code/buffer.c
@@ -1026,6 +1026,7 @@ Bool BufferClassCheck(BufferClass klass)
 DEFINE_CLASS(Inst, BufferClass, klass)
 {
   INHERIT_CLASS(klass, BufferClass, InstClass);
+  AVERT(InstClass, klass);
 }
 
 DEFINE_CLASS(Buffer, Buffer, klass)
@@ -1043,6 +1044,7 @@ DEFINE_CLASS(Buffer, Buffer, klass)
   klass->setRankSet = bufferNoSetRankSet;
   klass->reassignSeg = bufferNoReassignSeg;
   klass->sig = BufferClassSig;
+  AVERT(BufferClass, klass);
 }
 
 
@@ -1248,6 +1250,7 @@ DEFINE_CLASS(Buffer, SegBuf, klass)
   klass->rankSet = segBufRankSet;
   klass->setRankSet = segBufSetRankSet;
   klass->reassignSeg = segBufReassignSeg;
+  AVERT(BufferClass, klass);
 }
 
 
@@ -1304,6 +1307,7 @@ DEFINE_CLASS(Buffer, RankBuf, klass)
   INHERIT_CLASS(klass, RankBuf, SegBuf);
   klass->varargs = rankBufVarargs;
   klass->init = rankBufInit;
+  AVERT(BufferClass, klass);
 }
 
 
diff --git a/mps/code/cbs.c b/mps/code/cbs.c
index 16c6b63d1bc..db4fa5efb46 100644
--- a/mps/code/cbs.c
+++ b/mps/code/cbs.c
@@ -1151,18 +1151,21 @@ DEFINE_CLASS(Land, CBS, klass)
   klass->findLast = cbsFindLast;
   klass->findLargest = cbsFindLargest;
   klass->findInZones = cbsFindInZones;
+  AVERT(LandClass, klass);
 }
 
 DEFINE_CLASS(Land, CBSFast, klass)
 {
   INHERIT_CLASS(klass, CBSFast, CBS);
   klass->init = cbsInitFast;
+  AVERT(LandClass, klass);
 }
 
 DEFINE_CLASS(Land, CBSZoned, klass)
 {
   INHERIT_CLASS(klass, CBSZoned, CBSFast);
   klass->init = cbsInitZoned;
+  AVERT(LandClass, klass);
 }
 
 
diff --git a/mps/code/failover.c b/mps/code/failover.c
index 94b6b17b2fc..d4139e2fe8f 100644
--- a/mps/code/failover.c
+++ b/mps/code/failover.c
@@ -286,6 +286,7 @@ DEFINE_CLASS(Land, Failover, klass)
   klass->findLast = failoverFindLast;
   klass->findLargest = failoverFindLargest;
   klass->findInZones = failoverFindInZones;
+  AVERT(LandClass, klass);
 }
 
 
diff --git a/mps/code/freelist.c b/mps/code/freelist.c
index c4dba60d7ed..b3e2fde3112 100644
--- a/mps/code/freelist.c
+++ b/mps/code/freelist.c
@@ -794,6 +794,7 @@ DEFINE_CLASS(Land, Freelist, klass)
   klass->findLast = freelistFindLast;
   klass->findLargest = freelistFindLargest;
   klass->findInZones = freelistFindInZones;
+  AVERT(LandClass, klass);
 }
 
 
diff --git a/mps/code/land.c b/mps/code/land.c
index 82e85d884db..ce1ed275777 100644
--- a/mps/code/land.c
+++ b/mps/code/land.c
@@ -528,6 +528,7 @@ static Res LandAbsDescribe(Inst inst, mps_lib_FILE *stream, Count depth)
 DEFINE_CLASS(Inst, LandClass, klass)
 {
   INHERIT_CLASS(klass, LandClass, InstClass);
+  AVERT(InstClass, klass);
 }
 
 DEFINE_CLASS(Land, Land, klass)
@@ -547,6 +548,7 @@ DEFINE_CLASS(Land, Land, klass)
   klass->findLargest = landNoFind;
   klass->findInZones = landNoFindInZones;
   klass->sig = LandClassSig;
+  AVERT(LandClass, klass);
 }
 
 
diff --git a/mps/code/pool.c b/mps/code/pool.c
index 4c3f742ee47..68469172426 100644
--- a/mps/code/pool.c
+++ b/mps/code/pool.c
@@ -66,13 +66,6 @@ Bool PoolClassCheck(PoolClass klass)
          (klass->framePop == PoolNoFramePop));
   CHECKL((klass->rampBegin == PoolNoRampBegin) ==
          (klass->rampEnd == PoolNoRampEnd));
-
-  /* Check that pool classes that set attributes also override the
-     methods they imply. */
-  if (klass != &CLASS_STATIC(AbstractCollectPool)) {
-    /* FIXME: AttrGC iff segments are GCSeg with whiten, scan, fix,
-       reclaim methods. */
-  }
   
   CHECKS(PoolClass, klass);
   return TRUE;
diff --git a/mps/code/poolabs.c b/mps/code/poolabs.c
index fd3ba9292f9..685b3871740 100644
--- a/mps/code/poolabs.c
+++ b/mps/code/poolabs.c
@@ -146,6 +146,7 @@ void PoolAbsFinish(Inst inst)
 DEFINE_CLASS(Inst, PoolClass, klass)
 {
   INHERIT_CLASS(klass, PoolClass, InstClass);
+  AVERT(InstClass, klass);
 }
 
 DEFINE_CLASS(Pool, AbstractPool, klass)
@@ -171,24 +172,28 @@ DEFINE_CLASS(Pool, AbstractPool, klass)
   klass->totalSize = PoolNoSize;
   klass->freeSize = PoolNoSize;
   klass->sig = PoolClassSig;
+  AVERT(PoolClass, klass);
 }
 
 DEFINE_CLASS(Pool, AbstractBufferPool, klass)
 {
   INHERIT_CLASS(klass, AbstractBufferPool, AbstractPool);
   PoolClassMixInBuffer(klass);
+  AVERT(PoolClass, klass);
 }
 
 DEFINE_CLASS(Pool, AbstractSegBufPool, klass)
 {
   INHERIT_CLASS(klass, AbstractSegBufPool, AbstractBufferPool);
   klass->bufferClass = SegBufClassGet;
+  AVERT(PoolClass, klass);
 }
 
 DEFINE_CLASS(Pool, AbstractCollectPool, klass)
 {
   INHERIT_CLASS(klass, AbstractCollectPool, AbstractSegBufPool);
   PoolClassMixInCollect(klass);
+  AVERT(PoolClass, klass);
 }
 
 
diff --git a/mps/code/poolamc.c b/mps/code/poolamc.c
index 8ba8ef61666..2202a88a803 100644
--- a/mps/code/poolamc.c
+++ b/mps/code/poolamc.c
@@ -167,6 +167,20 @@ static Res AMCSegInit(Seg seg, Pool pool, Addr base, Size size, ArgList args)
 }
 
 
+/* amcSegFinish -- finish an AMC segment */
+
+static void amcSegFinish(Inst inst)
+{
+  Seg seg = MustBeA(Seg, inst);
+  amcSeg amcseg = MustBeA(amcSeg, seg);
+
+  amcseg->sig = SigInvalid;
+
+  /* finish the superclass fields last */
+  NextMethod(Inst, amcSeg, finish)(inst);
+}
+
+
 /* AMCSegSketch -- summarise the segment state for a human reader
  *
  * Write a short human-readable text representation of the segment 
@@ -339,6 +353,7 @@ DEFINE_CLASS(Seg, amcSeg, klass)
   INHERIT_CLASS(klass, amcSeg, GCSeg);
   SegClassMixInNoSplitMerge(klass);  /* no support for this (yet) */
   klass->instClassStruct.describe = AMCSegDescribe;
+  klass->instClassStruct.finish = amcSegFinish;
   klass->size = sizeof(amcSegStruct);
   klass->init = AMCSegInit;
   klass->whiten = amcSegWhiten;
@@ -347,6 +362,7 @@ DEFINE_CLASS(Seg, amcSeg, klass)
   klass->fixEmergency = amcSegFixEmergency;
   klass->reclaim = amcSegReclaim;
   klass->walk = amcSegWalk;
+  AVERT(SegClass, klass);
 }
 
 
@@ -538,6 +554,7 @@ DEFINE_CLASS(Buffer, amcBuf, klass)
   klass->instClassStruct.finish = AMCBufFinish;
   klass->size = sizeof(amcBufStruct);
   klass->init = AMCBufInit;
+  AVERT(BufferClass, klass);
 }
 
 
@@ -1999,6 +2016,7 @@ DEFINE_CLASS(Pool, AMCZPool, klass)
   klass->bufferClass = amcBufClassGet;
   klass->totalSize = AMCTotalSize;
   klass->freeSize = AMCFreeSize;  
+  AVERT(PoolClass, klass);
 }
 
 
@@ -2008,6 +2026,7 @@ DEFINE_CLASS(Pool, AMCPool, klass)
 {
   INHERIT_CLASS(klass, AMCPool, AMCZPool);
   klass->init = AMCInit;
+  AVERT(PoolClass, klass);
 }
 
 
diff --git a/mps/code/poolams.c b/mps/code/poolams.c
index cd4322eb95f..b959fbfd5c8 100644
--- a/mps/code/poolams.c
+++ b/mps/code/poolams.c
@@ -1793,6 +1793,7 @@ DEFINE_CLASS(Pool, AMSDebugPool, klass)
   klass->size = sizeof(AMSDebugStruct);
   klass->varargs = AMSDebugVarargs;
   klass->debugMixin = AMSDebugMixin;
+  AVERT(PoolClass, klass);
 }
 
 
diff --git a/mps/code/poolawl.c b/mps/code/poolawl.c
index 04651177ef6..d08e53cc006 100644
--- a/mps/code/poolawl.c
+++ b/mps/code/poolawl.c
@@ -302,6 +302,7 @@ DEFINE_CLASS(Seg, AWLSeg, klass)
   klass->fixEmergency = awlSegFix;
   klass->reclaim = awlSegReclaim;
   klass->walk = awlSegWalk;
+  AVERT(SegClass, klass);
 }
 
 
@@ -1256,6 +1257,7 @@ DEFINE_CLASS(Pool, AWLPool, klass)
   klass->bufferEmpty = AWLBufferEmpty;
   klass->totalSize = AWLTotalSize;
   klass->freeSize = AWLFreeSize;
+  AVERT(PoolClass, klass);
 }
 
 
diff --git a/mps/code/poollo.c b/mps/code/poollo.c
index 8976cd5b58f..5ef7620644b 100644
--- a/mps/code/poollo.c
+++ b/mps/code/poollo.c
@@ -83,6 +83,7 @@ DEFINE_CLASS(Seg, LOSeg, klass)
   klass->fixEmergency = loSegFix;
   klass->reclaim = loSegReclaim;
   klass->walk = loSegWalk;
+  AVERT(SegClass, klass);
 }
 
 
@@ -792,6 +793,7 @@ DEFINE_CLASS(Pool, LOPool, klass)
   klass->bufferEmpty = LOBufferEmpty;
   klass->totalSize = LOTotalSize;
   klass->freeSize = LOFreeSize;
+  AVERT(PoolClass, klass);
 }
 
 
diff --git a/mps/code/poolmfs.c b/mps/code/poolmfs.c
index 0152882392b..bf2203baff7 100644
--- a/mps/code/poolmfs.c
+++ b/mps/code/poolmfs.c
@@ -349,6 +349,7 @@ DEFINE_CLASS(Pool, MFSPool, klass)
   klass->free = MFSFree;
   klass->totalSize = MFSTotalSize;
   klass->freeSize = MFSFreeSize;  
+  AVERT(PoolClass, klass);
 }
 
 
diff --git a/mps/code/poolmrg.c b/mps/code/poolmrg.c
index 6f3eca57b8c..fbbaad87d26 100644
--- a/mps/code/poolmrg.c
+++ b/mps/code/poolmrg.c
@@ -234,6 +234,20 @@ static Res MRGLinkSegInit(Seg seg, Pool pool, Addr base, Size size,
 }
 
 
+/* MRGLinkSegFinish -- finish a link segment */
+
+static void mrgLinkSegFinish(Inst inst)
+{
+  Seg seg = MustBeA(Seg, inst);
+  MRGLinkSeg linkseg = MustBeA(MRGLinkSeg, seg);
+
+  linkseg->sig = SigInvalid;
+
+  /* finish the superclass fields last */
+  NextMethod(Inst, MRGLinkSeg, finish)(inst);
+}
+
+
 /* MRGRefSegInit -- initialise a ref segment */
 
 ARG_DEFINE_KEY(mrg_seg_link_seg, Pointer);
@@ -282,14 +296,30 @@ static Res MRGRefSegInit(Seg seg, Pool pool, Addr base, Size size, ArgList args)
 }
 
 
+/* MRGRefSegFinish -- finish a ref segment */
+
+static void mrgRefSegFinish(Inst inst)
+{
+  Seg seg = MustBeA(Seg, inst);
+  MRGRefSeg refseg = MustBeA(MRGRefSeg, seg);
+
+  refseg->sig = SigInvalid;
+
+  /* finish the superclass fields last */
+  NextMethod(Inst, MRGRefSeg, finish)(inst);
+}
+
+
 /* MRGLinkSegClass -- Class definition */
 
 DEFINE_CLASS(Seg, MRGLinkSeg, klass)
 {
   INHERIT_CLASS(klass, MRGLinkSeg, Seg);
   SegClassMixInNoSplitMerge(klass);  /* no support for this */
+  klass->instClassStruct.finish = mrgLinkSegFinish;
   klass->size = sizeof(MRGLinkSegStruct);
   klass->init = MRGLinkSegInit;
+  AVERT(SegClass, klass);
 }
 
 
@@ -299,9 +329,11 @@ DEFINE_CLASS(Seg, MRGRefSeg, klass)
 {
   INHERIT_CLASS(klass, MRGRefSeg, GCSeg);
   SegClassMixInNoSplitMerge(klass);  /* no support for this */
+  klass->instClassStruct.finish = mrgRefSegFinish;
   klass->size = sizeof(MRGRefSegStruct);
   klass->init = MRGRefSegInit;
   klass->scan = mrgRefSegScan;
+  AVERT(SegClass, klass);
 }
 
 
@@ -472,7 +504,6 @@ static void MRGSegPairDestroy(MRGRefSeg refseg)
 {
   RingRemove(&refseg->mrgRing);
   RingFinish(&refseg->mrgRing);
-  refseg->sig = SigInvalid;
   SegFree(MustBeA(Seg, refseg->linkSeg));
   SegFree(MustBeA(Seg, refseg));
 }
@@ -834,6 +865,7 @@ DEFINE_CLASS(Pool, MRGPool, klass)
   klass->instClassStruct.finish = MRGFinish;
   klass->size = sizeof(MRGStruct);
   klass->init = MRGInit;
+  AVERT(PoolClass, klass);
 }
 
 
diff --git a/mps/code/poolmv.c b/mps/code/poolmv.c
index ed49df28c66..045a56eba84 100644
--- a/mps/code/poolmv.c
+++ b/mps/code/poolmv.c
@@ -873,6 +873,7 @@ DEFINE_CLASS(Pool, MVPool, klass)
   klass->free = MVFree;
   klass->totalSize = MVTotalSize;
   klass->freeSize = MVFreeSize;
+  AVERT(PoolClass, klass);
 }
 
 
@@ -891,6 +892,7 @@ DEFINE_CLASS(Pool, MVDebugPool, klass)
   klass->size = sizeof(MVDebugStruct);
   klass->varargs = MVDebugVarargs;
   klass->debugMixin = MVDebugMixin;
+  AVERT(PoolClass, klass);
 }
 
 
diff --git a/mps/code/poolmv2.c b/mps/code/poolmv2.c
index b78eb29d2f2..1a8f0bdb12e 100644
--- a/mps/code/poolmv2.c
+++ b/mps/code/poolmv2.c
@@ -149,6 +149,7 @@ DEFINE_CLASS(Pool, MVTPool, klass)
   klass->bufferEmpty = MVTBufferEmpty;
   klass->totalSize = MVTTotalSize;
   klass->freeSize = MVTFreeSize;
+  AVERT(PoolClass, klass);
 }
 
 /* Macros */
diff --git a/mps/code/poolmvff.c b/mps/code/poolmvff.c
index b229f94cf26..287559675e9 100644
--- a/mps/code/poolmvff.c
+++ b/mps/code/poolmvff.c
@@ -741,6 +741,7 @@ DEFINE_CLASS(Pool, MVFFPool, klass)
   klass->bufferEmpty = MVFFBufferEmpty;
   klass->totalSize = MVFFTotalSize;
   klass->freeSize = MVFFFreeSize;
+  AVERT(PoolClass, klass);
 }
 
 
@@ -759,6 +760,7 @@ DEFINE_CLASS(Pool, MVFFDebugPool, klass)
   klass->size = sizeof(MVFFDebugStruct);
   klass->varargs = MVFFDebugVarargs;
   klass->debugMixin = MVFFDebugMixin;
+  AVERT(PoolClass, klass);
 }
 
 
diff --git a/mps/code/poolsnc.c b/mps/code/poolsnc.c
index a9f018a6a68..1150c74ad7c 100644
--- a/mps/code/poolsnc.c
+++ b/mps/code/poolsnc.c
@@ -163,6 +163,7 @@ DEFINE_CLASS(Buffer, SNCBuf, klass)
   klass->instClassStruct.finish = SNCBufFinish;
   klass->size = sizeof(SNCBufStruct);
   klass->init = SNCBufInit;
+  AVERT(BufferClass, klass);
 }
 
 
@@ -227,16 +228,32 @@ static Res sncSegInit(Seg seg, Pool pool, Addr base, Size size, ArgList args)
 }
 
 
+/* sncSegFinish -- finish an SNC segment */
+
+static void sncSegFinish(Inst inst)
+{
+  Seg seg = MustBeA(Seg, inst);
+  SNCSeg sncseg = MustBeA(SNCSeg, seg);
+
+  sncseg->sig = SigInvalid;
+
+  /* finish the superclass fields last */
+  NextMethod(Inst, SNCSeg, finish)(inst);
+}
+
+
 /* SNCSegClass -- Class definition for SNC segments */
 
 DEFINE_CLASS(Seg, SNCSeg, klass)
 {
   INHERIT_CLASS(klass, SNCSeg, GCSeg);
   SegClassMixInNoSplitMerge(klass);  /* no support for this (yet) */
+  klass->instClassStruct.finish = sncSegFinish;
   klass->size = sizeof(SNCSegStruct);
   klass->init = sncSegInit;
   klass->scan = sncSegScan;
   klass->walk = sncSegWalk;
+  AVERT(SegClass, klass);
 }
 
 
@@ -680,6 +697,7 @@ DEFINE_CLASS(Pool, SNCPool, klass)
   klass->bufferClass = SNCBufClassGet;
   klass->totalSize = SNCTotalSize;
   klass->freeSize = SNCFreeSize;
+  AVERT(PoolClass, klass);
 }
 
 
diff --git a/mps/code/protocol.c b/mps/code/protocol.c
index 1f3a648975c..afa03344247 100644
--- a/mps/code/protocol.c
+++ b/mps/code/protocol.c
@@ -22,6 +22,7 @@ DEFINE_CLASS(Inst, Inst, klass)
 {
   InstClassInitInternal(klass);
   klass->instStruct.klass = CLASS(InstClass);
+  AVERT(InstClass, klass);
 }
 
 DEFINE_CLASS(Inst, InstClass, klass)
@@ -34,6 +35,7 @@ DEFINE_CLASS(Inst, InstClass, klass)
   klass->name = "InstClass";
   klass->level = ClassLevelInstClass;
   klass->display[ClassLevelInstClass] = CLASS_ID(InstClass);
+  AVERT(InstClass, klass);
 }
 
 static void InstClassInitInternal(InstClass klass)
diff --git a/mps/code/seg.c b/mps/code/seg.c
index 6ee70bd9bb0..2fb2335c1db 100644
--- a/mps/code/seg.c
+++ b/mps/code/seg.c
@@ -1991,6 +1991,16 @@ Bool SegClassCheck(SegClass klass)
   CHECKL(FUNCHECK(klass->fixEmergency));
   CHECKL(FUNCHECK(klass->reclaim));
   CHECKL(FUNCHECK(klass->walk));
+
+  /* Check that segment classes override sets of related methods. */
+  AVER((klass->init == SegAbsInit)
+       == (klass->instClassStruct.finish == SegAbsFinish));
+  AVER((klass->init == gcSegInit)
+       == (klass->instClassStruct.finish == gcSegFinish));
+  AVER((klass->merge == segTrivMerge) == (klass->split == segTrivSplit));
+  AVER((klass->fix == segNoFix) == (klass->fixEmergency == segNoFix));
+  AVER((klass->fix == segNoFix) == (klass->reclaim == segNoReclaim));
+
   CHECKS(SegClass, klass);
   return TRUE;
 }
@@ -2001,6 +2011,7 @@ Bool SegClassCheck(SegClass klass)
 DEFINE_CLASS(Inst, SegClass, klass)
 {
   INHERIT_CLASS(klass, SegClass, InstClass);
+  AVERT(InstClass, klass);
 }
 
 DEFINE_CLASS(Seg, Seg, klass)
diff --git a/mps/code/segsmss.c b/mps/code/segsmss.c
index 2e3fa32297a..b2f12d3ec9a 100644
--- a/mps/code/segsmss.c
+++ b/mps/code/segsmss.c
@@ -655,6 +655,7 @@ DEFINE_CLASS(Pool, AMSTPool, klass)
   klass->size = sizeof(AMSTStruct);
   klass->init = AMSTInit;
   klass->bufferFill = AMSTBufferFill;
+  AVERT(PoolClass, klass);
 }