Make sure the dbFileVers field in the Pager object is properly initialized

even if there is an I/O error while reading its content off of disk.

FossilOrigin-Name: 81ff698f62c8133818a3db1997ae7427705da23f

manifest

@@ -1,5 +1,8 @@
-C Change\sa\scondition\sin\ssqlite3VdbeMemShallowCopy()\sto\savoid\saccessing\san\sunitialized\svariable\s(doing\sso\swas\snot\sdangerous,\sbut\scaused\sa\svalgrind\serror).
+-----BEGIN PGP SIGNED MESSAGE-----
-D 2010-03-05T18:46:12
+Hash: SHA1
+
+C Make\ssure\sthe\sdbFileVers\sfield\sin\sthe\sPager\sobject\sis\sproperly\sinitialized\neven\sif\sthere\sis\san\sI/O\serror\swhile\sreading\sits\scontent\soff\sof\sdisk.
+D 2010-03-05T20:17:46
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 F Makefile.in 4f2f967b7e58a35bb74fb7ec8ae90e0f4ca7868b
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -152,7 +155,7 @@ F src/os_common.h 240c88b163b02c21a9f21f87d49678a0aa21ff30
 F src/os_os2.c 75a8c7b9a00a2cf1a65f9fa4afbc27d46634bb2f
 F src/os_unix.c 148d2f625db3727250c0b880481ae7630b6d0eb0
 F src/os_win.c 1c7453c2df4dab26d90ff6f91272aea18bcf7053
-F src/pager.c ace73a84f53a551fb8b9334205af210a29874b2c
+F src/pager.c aafc314dee6e55be6cd6b4b1f9f8de62f0e1dfcc
 F src/pager.h 1b32faf2e578ac3e7bcf9c9d11217128261c5c54
 F src/parse.y ace5c7a125d9f2a410e431ee3209034105045f7e
 F src/pcache.c 4956b41d6ba913f7a8a56fbf32be78caed0e45c2
@@ -792,7 +795,14 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
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manifest.uuid

@@ -1 +1 @@
-4793c381c6ff4e4d25433298be30028721a9cb67
+81ff698f62c8133818a3db1997ae7427705da23f

src/pager.c

@@ -3339,6 +3339,7 @@ int sqlite3PagerOpen(
   /* pPager->pBusyHandlerArg = 0; */
   pPager->xReiniter = xReinit;
   /* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */
+
   *ppPager = pPager;
   return SQLITE_OK;
 }
@@ -3488,9 +3489,25 @@ static int readDbPage(PgHdr *pPg){
     rc = SQLITE_OK;
   }
   if( pgno==1 ){
+    if( rc ){
+      /* If the read is unsuccessful, set the dbFileVers[] to something
+      ** that will never be a valid file version.  dbFileVers[] is a copy
+      ** of bytes 24..39 of the database.  Bytes 28..31 should always be
+      ** zero.  Bytes 32..35 and 35..39 should be page numbers which are
+      ** never 0xffffffff.  So filling pPager->dbFileVers[] with all 0xff
+      ** bytes should suffice.
+      **
+      ** For an encrypted database, the situation is more complex:  bytes
+      ** 24..39 of the database are white noise.  But the probability of
+      ** white noising equaling 16 bytes of 0xff is vanishingly small so
+      ** we should still be ok.
+      */
+      memset(pPager->dbFileVers, 0xff, sizeof(pPager->dbFileVers));
+    }else{
       u8 *dbFileVers = &((u8*)pPg->pData)[24];
       memcpy(&pPager->dbFileVers, dbFileVers, sizeof(pPager->dbFileVers));
     }
+  }
   CODEC1(pPager, pPg->pData, pgno, 3, rc = SQLITE_NOMEM);
 
   PAGER_INCR(sqlite3_pager_readdb_count);