Implement a sanity check for CCS fields in profiling builds

This helped me debug one of the bugs in #15508. I'm not sure if this is
a good idea, but it worked for me, so wanted to submit this as a MR.

1 files changed, 13 insertions, 0 deletions

diff --git a/rts/Arena.c b/rts/Arena.c
index cd547e5b33..e0b4ebde30 100644
--- a/rts/Arena.c
+++ b/rts/Arena.c
@@ -117,3 +117,16 @@ arenaBlocks( void )
 {
     return arena_blocks;
 }
+
+#if defined(DEBUG)
+void checkPtrInArena( StgPtr p, Arena *arena )
+{
+    for (bdescr *bd = arena->current; bd; bd = bd->link) {
+        if (p >= bd->start && p < bd->free) {
+            return;
+        }
+    }
+
+    barf("Location %p is not in arena %p", (void*)p, (void*)arena);
+}
+#endif