branches/zip: btr0btr.c: Add more UNIV_BTR_DEBUG checks. This should

help in tracking down issue #63 (memory corruption).  UNIV_BTR_DEBUG
is currently enabled in univ.i.

btr_root_fseg_validate(): New function, for validating a file segment
header on a B-tree root page.

btr_root_block_get(), btr_free_but_not_root(),
btr_root_raise_and_insert(), btr_discard_only_page_on_level():
Check PAGE_BTR_SEG_LEAF and PAGE_BTR_SEG_TOP on the root page with
btr_root_fseg_validate().

btr_root_raise_and_insert(): Move the assertion
dict_index_get_page(index) == page_get_page_no(root)
inside UNIV_BTR_DEBUG.  It was previously enabled by UNIV_DEBUG.

btr_free_root(): Check PAGE_BTR_SEG_TOP on the root page with
btr_root_fseg_validate().

btr/btr0btr.c

@@ -78,6 +78,26 @@ make them consecutive on disk if possible. From the other file segment
 we allocate pages for the non-leaf levels of the tree.
 */
 
+#ifdef UNIV_BTR_DEBUG
+/******************************************************************
+Checks a file segment header within a B-tree root page. */
+static
+ibool
+btr_root_fseg_validate(
+/*===================*/
+						/* out: TRUE if valid */
+	const fseg_header_t*	seg_header,	/* in: segment header */
+	ulint			space)		/* in: tablespace identifier */
+{
+	ulint	offset = mach_read_from_2(seg_header + FSEG_HDR_OFFSET);
+
+	ut_a(mach_read_from_4(seg_header + FSEG_HDR_SPACE) == space);
+	ut_a(offset >= FIL_PAGE_DATA);
+	ut_a(offset <= UNIV_PAGE_SIZE - FIL_PAGE_DATA_END);
+	return(TRUE);
+}
+#endif /* UNIV_BTR_DEBUG */
+
 /******************************************************************
 Gets the root node of a tree and x-latches it. */
 static
@@ -100,6 +120,12 @@ btr_root_block_get(
 	block = btr_block_get(space, zip_size, root_page_no, RW_X_LATCH, mtr);
 	ut_a((ibool)!!page_is_comp(buf_block_get_frame(block))
 	     == dict_table_is_comp(index->table));
+#ifdef UNIV_BTR_DEBUG
+	ut_a(btr_root_fseg_validate(FIL_PAGE_DATA + PAGE_BTR_SEG_LEAF
+				    + buf_block_get_frame(block), space));
+	ut_a(btr_root_fseg_validate(FIL_PAGE_DATA + PAGE_BTR_SEG_TOP
+				    + buf_block_get_frame(block), space));
+#endif /* UNIV_BTR_DEBUG */
 
 	return(block);
 }
@@ -820,6 +846,12 @@ leaf_loop:
 	mtr_start(&mtr);
 
 	root = btr_page_get(space, zip_size, root_page_no, RW_X_LATCH, &mtr);
+#ifdef UNIV_BTR_DEBUG
+	ut_a(btr_root_fseg_validate(FIL_PAGE_DATA + PAGE_BTR_SEG_LEAF
+				    + root, space));
+	ut_a(btr_root_fseg_validate(FIL_PAGE_DATA + PAGE_BTR_SEG_TOP
+				    + root, space));
+#endif /* UNIV_BTR_DEBUG */
 
 	/* NOTE: page hash indexes are dropped when a page is freed inside
 	fsp0fsp. */
@@ -836,6 +868,10 @@ top_loop:
 	mtr_start(&mtr);
 
 	root = btr_page_get(space, zip_size, root_page_no, RW_X_LATCH, &mtr);
+#ifdef UNIV_BTR_DEBUG
+	ut_a(btr_root_fseg_validate(FIL_PAGE_DATA + PAGE_BTR_SEG_TOP
+				    + root, space));
+#endif /* UNIV_BTR_DEBUG */
 
 	finished = fseg_free_step_not_header(
 		root + PAGE_HEADER + PAGE_BTR_SEG_TOP, &mtr);
@@ -868,6 +904,9 @@ btr_free_root(
 	btr_search_drop_page_hash_index(block);
 
 	header = buf_block_get_frame(block) + PAGE_HEADER + PAGE_BTR_SEG_TOP;
+#ifdef UNIV_BTR_DEBUG
+	ut_a(btr_root_fseg_validate(header, space));
+#endif /* UNIV_BTR_DEBUG */
 
 	while (!fseg_free_step(header, mtr));
 }
@@ -1104,8 +1143,13 @@ btr_root_raise_and_insert(
 	ut_a(!root_page_zip || page_zip_validate(root_page_zip, root));
 #endif /* UNIV_ZIP_DEBUG */
 	index = btr_cur_get_index(cursor);
-
-	ut_ad(dict_index_get_page(index) == page_get_page_no(root));
+#ifdef UNIV_BTR_DEBUG
+	ut_a(btr_root_fseg_validate(FIL_PAGE_DATA + PAGE_BTR_SEG_LEAF
+				    + root, dict_index_get_space(index)));
+	ut_a(btr_root_fseg_validate(FIL_PAGE_DATA + PAGE_BTR_SEG_TOP
+				    + root, dict_index_get_space(index)));
+	ut_a(dict_index_get_page(index) == page_get_page_no(root));
+#endif /* UNIV_BTR_DEBUG */
 	ut_ad(mtr_memo_contains(mtr, dict_index_get_lock(index),
 				MTR_MEMO_X_LOCK));
 	ut_ad(mtr_memo_contains(mtr, root_block, MTR_MEMO_PAGE_X_FIX));
@@ -2651,6 +2695,14 @@ btr_discard_only_page_on_level(
 			== dict_index_get_page(index))) {
 		/* The father is the root page */
 
+#ifdef UNIV_BTR_DEBUG
+		const page_t*	root = buf_block_get_frame(father_block);
+		const ulint	space = dict_index_get_space(index);
+		ut_a(btr_root_fseg_validate(FIL_PAGE_DATA + PAGE_BTR_SEG_LEAF
+					    + root, space));
+		ut_a(btr_root_fseg_validate(FIL_PAGE_DATA + PAGE_BTR_SEG_TOP
+					    + root, space));
+#endif /* UNIV_BTR_DEBUG */
 		btr_page_empty(father_block, father_page_zip, mtr, index);
 
 		/* We play safe and reset the free bits for the father */