Remove an assert ("assert( subpage>0 )") from btree.c that may not be true for a corrupt database. Also add comments and other assert() statements to btree.c function moveToRoot(). (CVS 6886)

FossilOrigin-Name: 3151dab9c78106217ec80ebadc666dfd11b42029

manifest

@@ -1,5 +1,5 @@
-C Remove\sa\scase\sfrom\sBtreeMovetoUnpacked()\sthat\sis\sunreachable\sas\sof\s(6881).\s(CVS\s6885)
+C Remove\san\sassert\s("assert(\ssubpage>0\s)")\sfrom\sbtree.c\sthat\smay\snot\sbe\strue\sfor\sa\scorrupt\sdatabase.\sAlso\sadd\scomments\sand\sother\sassert()\sstatements\sto\sbtree.c\sfunction\smoveToRoot().\s(CVS\s6886)
-D 2009-07-13T07:30:53
+D 2009-07-13T09:41:45
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in df9359da7a726ccb67a45db905c5447d5c00c6ef
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -106,7 +106,7 @@ F src/auth.c 802a9439dfa0b8c208b10055cba400e82ef18025
 F src/backup.c 6f1c2d9862c8a3feb7739dfcca02c1f5352e37f3
 F src/bitvec.c 0ef0651714728055d43de7a4cdd95e703fac0119
 F src/btmutex.c 9b899c0d8df3bd68f527b0afe03088321b696d3c
-F src/btree.c 48825008514537420283ee9e51e0456263a39d2c
+F src/btree.c a65e2050dacd0a5dc046c488f351588146fd5e3e
 F src/btree.h e53a10fd31d16c60a86f03c9467a6f470aa3683b
 F src/btreeInt.h a568bf057aa249eb06fd31358b4393a5ac88c118
 F src/build.c 867028ee9f63f7bc8eb8d4a720bb98cf9b9a12b4
@@ -280,7 +280,7 @@ F test/collateA.test b8218ab90d1fa5c59dcf156efabb1b2599c580d6
 F test/colmeta.test 087c42997754b8c648819832241daf724f813322
 F test/colname.test 08948a4809d22817e0e5de89c7c0a8bd90cb551b
 F test/conflict.test 0ed68b11f22721052d880ee80bd528a0e0828236
-F test/corrupt.test e940096bcfac0399d09c5351c0d6ea610477c08a
+F test/corrupt.test 04e717ebb644f1b30b142cb5f30797747ef5f02f
 F test/corrupt2.test a571e30ea4e82318f319a24b6cc55935ce862079
 F test/corrupt3.test 263e8bb04e2728df832fddf6973cf54c91db0c32
 F test/corrupt4.test acdb01afaedf529004b70e55de1a6f5a05ae7fff
@@ -740,7 +740,7 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl 672f81d693a03f80f5ae60bfefacd8a349e76746
-P dfb146ef003bae8ff216baf68cc43d7eb7855c68
+P 39ce2097da03176e256a2ff35bb857e578f3ca2d
-R 7c7f4c4080ad2dff72d55dd2065d8da8
+R 0dc08162ecc49e81bc056e17b96d72d2
 U danielk1977
-Z 6fc9b62a7a8b05ddc28addf8e5619108
+Z b2bdf8d1bff20b39f70f8c184167a4bf

manifest.uuid

@@ -1 +1 @@
-39ce2097da03176e256a2ff35bb857e578f3ca2d
+3151dab9c78106217ec80ebadc666dfd11b42029

src/btree.c

@@ -9,7 +9,7 @@
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
-** $Id: btree.c,v 1.683 2009/07/13 07:30:53 danielk1977 Exp $
+** $Id: btree.c,v 1.684 2009/07/13 09:41:45 danielk1977 Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** See the header comment on "btreeInt.h" for additional information.
@@ -3974,7 +3974,25 @@ static void moveToParent(BtCursor *pCur){
 }
 
 /*
-** Move the cursor to the root page
+** Move the cursor to point to the root page of its b-tree structure.
+**
+** If the table has a virtual root page, then the cursor is moved to point
+** to the virtual root page instead of the actual root page. A table has a
+** virtual root page when the actual root page contains no cells and a 
+** single child page. This can only happen with the table rooted at page 1.
+**
+** If the b-tree structure is empty, the cursor state is set to 
+** CURSOR_INVALID. Otherwise, the cursor is set to point to the first
+** cell located on the root (or virtual root) page and the cursor state
+** is set to CURSOR_VALID.
+**
+** If this function returns successfully, it may be assumed that the
+** page-header flags indicate that the [virtual] root-page is the expected 
+** kind of b-tree page (i.e. if when opening the cursor the caller did not
+** specify a KeyInfo structure the flags byte is set to 0x05 or 0x0D,
+** indicating a table b-tree, or if the caller did specify a KeyInfo 
+** structure the flags byte is set to 0x02 or 0x0A, indicating an index
+** b-tree).
 */
 static int moveToRoot(BtCursor *pCur){
   MemPage *pRoot;
@@ -3988,6 +4006,7 @@ static int moveToRoot(BtCursor *pCur){
   assert( CURSOR_FAULT   > CURSOR_REQUIRESEEK );
   if( pCur->eState>=CURSOR_REQUIRESEEK ){
     if( pCur->eState==CURSOR_FAULT ){
+      assert( pCur->skip!=SQLITE_OK );
       return pCur->skip;
     }
     sqlite3BtreeClearCursor(pCur);
@@ -4018,8 +4037,16 @@ static int moveToRoot(BtCursor *pCur){
     }
   }
 
+  /* Assert that the root page is of the correct type. This must be the
+  ** case as the call to this function that loaded the root-page (either
+  ** this call or a previous invocation) would have detected corruption 
+  ** if the assumption were not true, and it is not possible for the flags 
+  ** byte to have been modified while this cursor is holding a reference
+  ** to the page.  */
   pRoot = pCur->apPage[0];
   assert( pRoot->pgno==pCur->pgnoRoot );
+  assert( pRoot->isInit && (pCur->pKeyInfo==0)==pRoot->intKey );
+
   pCur->aiIdx[0] = 0;
   pCur->info.nSize = 0;
   pCur->atLast = 0;
@@ -4028,9 +4055,7 @@ static int moveToRoot(BtCursor *pCur){
   if( pRoot->nCell==0 && !pRoot->leaf ){
     Pgno subpage;
     if( pRoot->pgno!=1 ) return SQLITE_CORRUPT_BKPT;
-    assert( pRoot->pgno==1 );
     subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+8]);
-    assert( subpage>0 );
     pCur->eState = CURSOR_VALID;
     rc = moveToChild(pCur, subpage);
   }else{
@@ -6418,6 +6443,7 @@ int sqlite3BtreeInsert(
   pPage = pCur->apPage[pCur->iPage];
   assert( pPage->intKey || nKey>=0 );
   assert( pPage->leaf || !pPage->intKey );
+
   TRACE(("INSERT: table=%d nkey=%lld ndata=%d page=%d %s\n",
           pCur->pgnoRoot, nKey, nData, pPage->pgno,
           loc==0 ? "overwrite" : "new entry"));

test/corrupt.test

@@ -13,7 +13,7 @@
 # This file implements tests to make sure SQLite does not crash or
 # segfault if it sees a corrupt database file.
 #
-# $Id: corrupt.test,v 1.11 2009/07/11 17:39:42 danielk1977 Exp $
+# $Id: corrupt.test,v 1.12 2009/07/13 09:41:45 danielk1977 Exp $
 
 catch {file delete -force test.db test.db-journal test.bu}
 
@@ -206,4 +206,24 @@ do_test corrupt-4.2 {
   catchsql { DELETE FROM t1 WHERE rowid = 3 }
 } {1 {database disk image is malformed}}
 
+do_test corrupt-5.1 {
+  db close
+  file delete -force test.db test.db-journal
+  sqlite3 db test.db
+
+  execsql { PRAGMA page_size = 1024 }
+  set ct "CREATE TABLE t1(c0 "
+  set i 0
+  while {[string length $ct] < 950} { append ct ", c[incr i]" }
+  append ct ")"
+  execsql $ct
+} {}
+
+do_test corrupt-5.2 {
+  db close
+  hexio_write test.db 108 00000000 
+  sqlite3 db test.db
+  catchsql { SELECT * FROM sqlite_master }
+} {1 {database disk image is malformed}}
+
 finish_test