SQLite

    /* Read the page-size and sector-size journal header fields. */
    if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+20, &iSectorSize))
     || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+24, &iPageSize))
    ){
      return rc;
    }

    /* Versions of SQLite prior to 3.5.8 set the page-size field of the
    ** journal header to zero. In this case, assume that the Pager.pageSize
    ** variable is already set to the correct page size.
    */
    if( iPageSize==0 ){
      iPageSize = pPager->pageSize;
    }

    /* Check that the values read from the page-size and sector-size fields
    ** are within range. To be 'in range', both values need to be a power
    ** of two greater than or equal to 512 or 32, and not greater than their 
    ** respective compile time maximum limits.
    */
    if( iPageSize<512                  || iSectorSize<32

# for documentation of the available commands.
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl
source $testdir/lock_common.tcl
source $testdir/malloc_common.tcl
db close

# Search for binaries to test against. Any executable files that match
# our naming convention are assumed to be testfixture binaries to test
# against.
#
set binaries [list]
set pattern "[file tail [info nameofexec]]*"
foreach file [glob $pattern] {
  if {[file executable $file]} {lappend binaries $file}
}
if {[llength $binaries]==0} {
  puts "WARNING: No binaries to test against. No tests have been run."
  finish_test
  return
}
proc get_version {binary} {
  set chan [launch_testfixture $binary]
  set v [testfixture $chan { sqlite3 -version }]
  close $chan
  set v
}
foreach bin $binaries {
  puts "Testing against $bin - version [get_version $bin]"
}

proc do_backcompat_test {rv bin1 bin2 script} {

  file delete -force test.db

  if {$bin1 != ""} { set ::bc_chan1 [launch_testfixture $bin1] }
  set ::bc_chan2 [launch_testfixture $bin2]

  if { $rv } {

    proc code2 {tcl} { uplevel #0 $tcl }
    if {$bin1 != ""} { proc code2 {tcl} { testfixture $::bc_chan1 $tcl } }
    proc code1 {tcl} { testfixture $::bc_chan2 $tcl }
  } else {
    proc code1 {tcl} { uplevel #0 $tcl }
    if {$bin1 != ""} { proc code1 {tcl} { testfixture $::bc_chan1 $tcl } }
    proc code2 {tcl} { testfixture $::bc_chan2 $tcl }
  }

  proc sql1 sql { code1 [list db eval $sql] }
  proc sql2 sql { code2 [list db eval $sql] }




  code1 { sqlite3 db test.db }
  code2 { sqlite3 db test.db }

  uplevel $script

  catch { code1 { db close } }
  catch { code2 { db close } }
  catch { close $::bc_chan2 }
  catch { close $::bc_chan1 }
}

array set ::incompatible [list]
proc do_allbackcompat_test {script} {

  foreach bin $::binaries {
    set nErr [set_test_counter errors]
    foreach dir {0 1} {

      set ::bcname ".[string map {testfixture {}} $bin].$dir."

      rename do_test _do_test
      proc do_test {nm sql res} {
        set nm [regsub {\.} $nm $::bcname]
        uplevel [list _do_test $nm $sql $res]
      }

      do_backcompat_test $dir {} $bin $script

      rename do_test {}
      rename _do_test do_test
    }
    if { $nErr < [set_test_counter errors] } {
      set ::incompatible([get_version $bin]) 1
    }

  do_test backcompat-1.1.4 { sql1 { SELECT * FROM t1; } } {abc def ghi jkl}
  do_test backcompat-1.1.5 { sql1 { PRAGMA integrity_check } } {ok}
  do_test backcompat-1.1.6 { sql2 { PRAGMA integrity_check } } {ok}

  # Test that one version can roll back a hot-journal file left in the
  # file-system by the other version.
  #
  # Each test case is named "backcompat-1.X...", where X is either 0 or
  # 1. If it is 0, then the current version creates a journal file that
  # the old versions try to read. Otherwise, if X is 1, then the old version
  # creates the journal file and we try to read it with the current version.
  #
  do_test backcompat-1.2.1 { sql1 {
    PRAGMA cache_size = 10;
    BEGIN;
      INSERT INTO t1 VALUES(randomblob(400), randomblob(400));
      INSERT INTO t1 SELECT randomblob(400), randomblob(400) FROM t1;
      INSERT INTO t1 SELECT randomblob(400), randomblob(400) FROM t1;
      INSERT INTO t1 SELECT randomblob(400), randomblob(400) FROM t1;
      INSERT INTO t1 SELECT randomblob(400), randomblob(400) FROM t1;
    COMMIT;
  } } {}
  set cksum1 [sql1 {SELECT md5sum(a), md5sum(b) FROM t1}]
  set cksum2 [sql2 {SELECT md5sum(a), md5sum(b) FROM t1}]
  do_test backcompat-1.2.2 [list string compare $cksum1 $cksum2] 0

  do_test backcompat-1.2.3 { sql1 {
    BEGIN;
      UPDATE t1 SET a = randomblob(500);
  } } {}
  set data [read_file_system]

  set f "test.db-journal[incr x]"
  file copy -force test.db-journal $f

  do_test backcompat-1.2.4 { sql1 { COMMIT } } {}

  set same [expr {[sql2 {SELECT md5sum(a), md5sum(b) FROM t1}] == $cksum2}]
  do_test backcompat-1.2.5 [list set {} $same] 0

  code1 { db close }
  code2 { db close }
  write_file_system $data
  code1 { sqlite3 db test.db }
  code2 { sqlite3 db test.db }

  set same [expr {[sql2 {SELECT md5sum(a), md5sum(b) FROM t1}] == $cksum2}]
  do_test backcompat-1.2.6 [list set {} $same] 1

  do_test backcompat-1.2.7 { sql1 { PRAGMA integrity_check } } {ok}
  do_test backcompat-1.2.8 { sql2 { PRAGMA integrity_check } } {ok}
}

foreach k [lsort [array names ::incompatible]] {
  puts "ERROR: Detected incompatibility with version $k"
}

finish_test