branches/zip:

buf_flush_init_for_writing(): The reported dense page directory size was
4 bytes too much.  Subtract 2 (infimum and supremum) from n_heap.

page_zip_decompress(): When decompressing the last user record, only set
heap_no and the status bits if there is data to decode, i.e., there
are user records on the page.

buf/buf0flu.c

@@ -502,7 +502,7 @@ buf_flush_init_for_writing(
 						+ (PAGE_HEADER + PAGE_LEVEL)),
 				(ulong) page_zip->m_start,
 				(ulong) 2
-				* page_dir_get_n_heap(page_zip->data));
+				* (page_dir_get_n_heap(page_zip->data) - 2));
 
 			page_zip->data = NULL;
 		}

page/page0zip.c

@@ -682,8 +682,10 @@ page_zip_decompress(
 	ut_a(d_stream.avail_out < UNIV_PAGE_SIZE
 				- PAGE_ZIP_START - PAGE_DIR);
 
-	/* set heap_no and the status bits */
-	mach_write_to_2(dst - REC_NEW_HEAP_NO, heap_status);
+	if (UNIV_LIKELY(d_stream.avail_out != 0)) {
+		/* set heap_no and the status bits */
+		mach_write_to_2(dst - REC_NEW_HEAP_NO, heap_status);
+	}
 
 	err = inflate(&d_stream, Z_FINISH);