From b3e8eb2280594da3cc45bc98ed8268fa36d2a2ad Mon Sep 17 00:00:00 2001
From: Gareth Rees <gdr@ravenbrook.com>
Date: Fri, 7 Aug 2015 16:14:50 +0100
Subject: [PATCH] The primary chunk is always the last chunk to be removed, so
 assert that. review suggestion from rb; see
 <https://info.ravenbrook.com/mail/2015/08/07/13-56-51/0/>

Copied from Perforce
 Change: 188089
 ServerID: perforce.ravenbrook.com
---
 mps/code/arena.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/mps/code/arena.c b/mps/code/arena.c
index 6327b791b59..95355935c57 100644
--- a/mps/code/arena.c
+++ b/mps/code/arena.c
@@ -701,12 +701,16 @@ void ArenaChunkRemoved(Arena arena, Chunk chunk)
   AVERT(Arena, arena);
   AVERT(Chunk, chunk);
 
-  if (arena->primary == chunk)
-    arena->primary = NULL;
-
   size = ChunkReserved(chunk);
   AVER(arena->reserved >= size);
   arena->reserved -= size;
+
+  if (chunk == arena->primary) {
+    /* The primary chunk must be the last chunk to be removed. */
+    AVER(RingIsSingle(&arena->chunkRing));
+    AVER(arena->reserved == 0);
+    arena->primary = NULL;
+  }
 }