Fix assertion failure due to over-eager code deduplication.

In the previous commit I'd made MemoryContextContains() use
GetMemoryChunkContext(), but that causes trouble when the passed
pointer isn't allocated in any memory context - that's probably
something we shouldn't do, but the previous commit isn't a place for a
"policy" change.

diff --git a/src/backend/utils/mmgr/mcxt.c b/src/backend/utils/mmgr/mcxt.c
index 07732ba59bcd7ee0c0e3fe6f01ffa802321b38d3..6668bf135e9a81435c9a74bdec9898c0d5d6f67a 100644 (file)
--- a/src/backend/utils/mmgr/mcxt.c
+++ b/src/backend/utils/mmgr/mcxt.c
@@ -566,7 +566,24 @@ MemoryContextCheck(MemoryContext context)
 bool
 MemoryContextContains(MemoryContext context, void *pointer)
 {
-       MemoryContext ptr_context = GetMemoryChunkContext(pointer);
+       MemoryContext ptr_context;
+
+       /*
+        * NB: Can't use GetMemoryChunkContext() here - that performs assertions
+        * that aren't acceptable here since we might be passed memory not
+        * allocated by any memory context.
+        *
+        * Try to detect bogus pointers handed to us, poorly though we can.
+        * Presumably, a pointer that isn't MAXALIGNED isn't pointing at an
+        * allocated chunk.
+        */
+       if (pointer == NULL || pointer != (void *) MAXALIGN(pointer))
+               return false;
+
+       /*
+        * OK, it's probably safe to look at the context.
+        */
+       ptr_context = *(MemoryContext *) (((char *) pointer) - sizeof(void *));
 
        return ptr_context == context;
 }