Fix an obscure problem with transactions written in "PRAGMA synchronous=full" mode on systems that do not support POWERSAFE_OVERWRITE causing an xSync() call to be omitted if the last frame written by a transaction is aligned to a sector boundary. This means that if a power failure or OS crash occurs very soon after such a transaction is committed, it may be lost following system recovery.

FossilOrigin-Name: 37de3eab67f12ae1ce5bc8d5e541c64fc6b1fd80

manifest

@@ -1,5 +1,5 @@
-C Improvements\sto\sthe\sinitialization\sof\sthe\spush-down\sautomoton\sfor\sthe\nLemon-generated\sparser.\s\sSmaller\sand\sfaster.
-D 2016-05-24T00:40:54.799
+C Fix\san\sobscure\sproblem\swith\stransactions\swritten\sin\s"PRAGMA\ssynchronous=full"\smode\son\ssystems\sthat\sdo\snot\ssupport\sPOWERSAFE_OVERWRITE\scausing\san\sxSync()\scall\sto\sbe\somitted\sif\sthe\slast\sframe\swritten\sby\sa\stransaction\sis\saligned\sto\sa\ssector\sboundary.\sThis\smeans\sthat\sif\sa\spower\sfailure\sor\sOS\scrash\soccurs\svery\ssoon\safter\ssuch\sa\stransaction\sis\scommitted,\sit\smay\sbe\slost\sfollowing\ssystem\srecovery.
+D 2016-05-24T16:20:51.379
 F Makefile.in f59e0763ff448719fc1bd25513882b0567286317
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 306d73e854b1a92ea06e5d1e637faa5c44de53c7
@@ -394,7 +394,7 @@ F src/test2.c 5586f43fcd9a1be0830793cf9d354082c261b25b
 F src/test3.c d2c9efd2985ff8f5502ffd3253156984778d77d8
 F src/test4.c d168f83cc78d02e8d35567bb5630e40dcd85ac1e
 F src/test5.c 5a34feec76d9b3a86aab30fd4f6cc9c48cbab4c1
-F src/test6.c 2c014d4977efd6107ec9eef3dfdec56ac516f824
+F src/test6.c a684b7abd01352ab50cb79c0bf727e6b3f381a3d
 F src/test7.c 9c89a4f1ed6bb13af0ed805b8d782bd83fcd57e3
 F src/test8.c fa262391d3edea6490a71bfaa8fed477ccbbac75
 F src/test9.c bea1e8cf52aa93695487badedd6e1886c321ea60
@@ -456,7 +456,7 @@ F src/vdbesort.c 91fda3909326860382b0ca8aa251e609c6a9d62c
 F src/vdbetrace.c f75c5455d8cf389ef86a8bfdfd3177e0e3692484
 F src/vtab.c ce0f2ebb589b459b32c640b33af64bfa5b29aaf8
 F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
-F src/wal.c 4db22ed7e77bcf672b1a685d6ddeffba8d5be302
+F src/wal.c 02eeecc265f6ffd0597378f5d8ae9070b62a406a
 F src/wal.h 2f7c831cf3b071fa548bf2d5cac640846a7ff19c
 F src/walker.c 0f142b5bd3ed2041fc52d773880748b212e63354
 F src/where.c 0e54a03d11d4e99ad25528f42ff4c9a6fa7a23da
@@ -1356,6 +1356,7 @@ F test/walcksum.test bb234a1bb42248b3515d992b719708015c384278
 F test/walcrash.test 21038858cc552077b0522f50b0fa87e38139306a
 F test/walcrash2.test a0edab4e5390f03b99a790de89aad15d6ec70b36
 F test/walcrash3.test e426aa58122d20f2b9fbe9a507f9eb8cab85b8af
+F test/walcrash4.test 2907eaa670156daf41bb865c30a08ad13088262c
 F test/walfault.test 1f8389f7709877e9b4cc679033d71d6fe529056b
 F test/walhook.test ed00a40ba7255da22d6b66433ab61fab16a63483
 F test/walmode.test 4022fe03ae6e830583672caa101f046438a0473c
@@ -1493,7 +1494,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 3c2a770549d5bb65fcd6cc684e0a0ae6d641ac68
-R f0cfba4e984837df73820e425fc5291f
-U drh
-Z 2da99ff99cbfd3def15eb678236b100e
+P 3b28b68e232060f8b2fe2fe6fa478280da2006ff
+R 517787a46c326083f1c71f4f2bce6c10
+U dan
+Z 8b1bf46b6e26241c0a55d35f24f797fc

manifest.uuid

@@ -1 +1 @@
-3b28b68e232060f8b2fe2fe6fa478280da2006ff
+37de3eab67f12ae1ce5bc8d5e541c64fc6b1fd80

src/test6.c

@@ -215,7 +215,9 @@ static int writeListSync(CrashFile *pFile, int isCrash){
   }
 
 #ifdef TRACE_CRASHTEST
-  printf("Sync %s (is %s crash)\n", pFile->zName, (isCrash?"a":"not a"));
+  if( pFile ){
+    printf("Sync %s (is %s crash)\n", pFile->zName, (isCrash?"a":"not a"));
+  }
 #endif
 
   ppPtr = &g.pWriteList;
@@ -799,6 +801,27 @@ static int processDevSymArgs(
   return TCL_OK;
 }
 
+/*
+** tclcmd:   sqlite3_crash_now
+**
+** Simulate a crash immediately. This function does not return 
+** (writeListSync() calls exit(-1)).
+*/
+static int crashNowCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+  writeListSync(0, 1);
+  assert( 0 );
+  return TCL_OK;
+}
+
 /*
 ** tclcmd:   sqlite_crash_enable ENABLE
 **
@@ -1034,6 +1057,7 @@ int Sqlitetest6_Init(Tcl_Interp *interp){
 #ifndef SQLITE_OMIT_DISKIO
   Tcl_CreateObjCommand(interp, "sqlite3_crash_enable", crashEnableCmd, 0, 0);
   Tcl_CreateObjCommand(interp, "sqlite3_crashparams", crashParamsObjCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "sqlite3_crash_now", crashNowCmd, 0, 0);
   Tcl_CreateObjCommand(interp, "sqlite3_simulate_device", devSymObjCmd, 0, 0);
   Tcl_CreateObjCommand(interp, "unregister_devsim", dsUnregisterObjCmd, 0, 0);
   Tcl_CreateObjCommand(interp, "register_jt_vfs", jtObjCmd, 0, 0);

src/wal.c

@@ -3109,16 +3109,21 @@ int sqlite3WalFrames(
   ** past the sector boundary is written after the sync.
   */
   if( isCommit && (sync_flags & WAL_SYNC_TRANSACTIONS)!=0 ){
+    int bSync = 1;
     if( pWal->padToSectorBoundary ){
       int sectorSize = sqlite3SectorSize(pWal->pWalFd);
       w.iSyncPoint = ((iOffset+sectorSize-1)/sectorSize)*sectorSize;
+      bSync = (w.iSyncPoint==iOffset);
+      testcase( bSync );
       while( iOffset<w.iSyncPoint ){
         rc = walWriteOneFrame(&w, pLast, nTruncate, iOffset);
         if( rc ) return rc;
         iOffset += szFrame;
         nExtra++;
       }
-    }else{
+    }
+    if( bSync ){
+      assert( rc==SQLITE_OK );
       rc = sqlite3OsSync(w.pFd, sync_flags & SQLITE_SYNC_MASK);
     }
   }

test/walcrash4.test

@@ -0,0 +1,75 @@
+# 2010 May 25
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#
+
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+source $testdir/lock_common.tcl
+source $testdir/wal_common.tcl
+ifcapable !wal {finish_test ; return }
+set testprefix walcrash4
+
+#-------------------------------------------------------------------------
+# At one point, if "PRAGMA synchronous=full" is set and the platform
+# does not support POWERSAFE_OVERWRITE, and the last frame written to 
+# the wal file in a transaction is aligned with a sector boundary, the
+# xSync() call was omitted. 
+#
+# The following test verifies that this has been fixed.
+#
+do_execsql_test 1.0 {
+  PRAGMA autovacuum = 0;
+  PRAGMA page_size = 1024;
+  PRAGMA journal_mode = wal;
+  PRAGMA main.synchronous = full;
+} {wal}
+
+faultsim_save_and_close
+
+for {set nExtra 0} {$nExtra < 10} {incr nExtra} {
+  for {set i 0} {$i < 10} {incr i} {
+    do_test 1.nExtra=$nExtra.i=$i.1 {
+      faultsim_restore_and_reopen
+    
+      set fd [open crash.tcl w]
+      puts $fd [subst -nocommands {
+        sqlite3_crash_enable 1
+        sqlite3_test_control_pending_byte $::sqlite_pending_byte
+        sqlite3 db test.db -vfs crash
+        db eval {
+          BEGIN;
+          CREATE TABLE t1(x UNIQUE);
+        }
+        for {set e 2} {[set e] < ($nExtra+2)} {incr e} {
+          db eval "CREATE TABLE t[set e] (x)"
+        }
+        db eval {
+          INSERT INTO t1 VALUES( randomblob(170000) );
+          COMMIT;
+        }
+        sqlite3_crash_now
+      }]
+      close $fd
+    
+      set r [catch { exec [info nameofexec] crash.tcl >@stdout } msg]
+      list $r $msg
+    } {1 {child process exited abnormally}}
+  
+    do_execsql_test 1.nExtra=$nExtra.i=$i.2 { 
+      SELECT count(*) FROM t1;
+      PRAGMA integrity_check;
+    } {1 ok}
+  } 
+}
+
+
+finish_test