Index: src/wal.c
==================================================================
--- src/wal.c
+++ src/wal.c
@@ -2251,10 +2251,14 @@
     rc = SQLITE_NOMEM_BKPT;
     goto begin_unlocked_out;
   }
   aData = &aFrame[WAL_FRAME_HDRSIZE];
 
+  /* Check to see if a complete transaction has been appended to the
+  ** wal file since the heap-memory wal-index was created. If so, the
+  ** heap-memory wal-index is discarded and WAL_RETRY returned to
+  ** the caller.  */
   aSaveCksum[0] = pWal->hdr.aFrameCksum[0];
   aSaveCksum[1] = pWal->hdr.aFrameCksum[1];
   for(iOffset=walFrameOffset(pWal->hdr.mxFrame+1, pWal->hdr.szPage); 
       iOffset+szFrame<=szWal; 
       iOffset+=szFrame
@@ -2274,11 +2278,13 @@
       }
       break;
     }
     if( !walDecodeFrame(pWal, &pgno, &nTruncate, aData, aFrame) ) break;
 
-    /* If nTruncate is non-zero, this is a commit record. */
+    /* If nTruncate is non-zero, then a complete transaction has been
+    ** appended to this wal file. Set rc to WAL_RETRY and break out of
+    ** the loop.  */
     if( nTruncate ){
       rc = WAL_RETRY;
       break;
     }
   }

Index: test/walro2.test
==================================================================
--- test/walro2.test
+++ test/walro2.test
@@ -13,11 +13,12 @@
 #
 
 set testdir [file dirname $argv0]
 source $testdir/tester.tcl
 source $testdir/lock_common.tcl
-set ::testprefix walro
+source $testdir/wal_common.tcl
+set ::testprefix walro2
 
 # These tests are only going to work on unix.
 #
 if {$::tcl_platform(platform) != "unix"} {
   finish_test
@@ -118,12 +119,83 @@
   do_test 2.3.2 {
     sql3 { INSERT INTO t1 VALUES('i', 'j') }
     code3 { db3 close }
     sql1 { COMMIT } 
   } {}
-  breakpoint
   do_test 2.3.3 {
     sql1 { SELECT * FROM t1 }
   } {a b c d e f g h i j}
+
+
+  #-----------------------------------------------------------------------
+  # 3.1.*: That a readonly_shm connection can read a database file if both
+  #        the *-wal and *-shm files are zero bytes in size.
+  #
+  # 3.2.*: That it flushes the cache if, between transactions on a db with a
+  #        zero byte *-wal file, some other connection modifies the db, then
+  #        does "PRAGMA wal_checkpoint=truncate" to truncate the wal file
+  #        back to zero bytes in size.
+  #
+  # 3.3.*: That, if between transactions some other process wraps the wal
+  #        file, the readonly_shm client reruns recovery.
+  #
+  catch { code1 { db close } }
+  catch { code2 { db2 close } }
+  catch { code3 { db3 close } }
+  do_test 3.1.0 {
+    list [file exists test.db-wal] [file exists test.db-shm]
+  } {0 0}
+  do_test 3.1.1 {
+    close [open test.db-wal w]
+    close [open test.db-shm w]
+    code1 {
+      sqlite3 db file:test.db?readonly_shm=1
+    }
+    sql1 { SELECT * FROM t1 }
+  } {a b c d e f g h}
+
+  do_test 3.2.0 {
+    list [file size test.db-wal] [file size test.db-shm]
+  } {0 0}
+  do_test 3.2.1 {
+    code2 { sqlite3 db2 test.db }
+    sql2 { INSERT INTO t1 VALUES(1, 2) ; PRAGMA wal_checkpoint=truncate }
+    code2 { db2 close }
+    sql1 { SELECT * FROM t1 }
+  } {a b c d e f g h 1 2}
+  do_test 3.2.2 {
+    list [file size test.db-wal] [file size test.db-shm]
+  } {0 32768}
+
+  do_test 3.3.0 {
+    code2 { sqlite3 db2 test.db }
+    sql2 { 
+      INSERT INTO t1 VALUES(3, 4);
+      INSERT INTO t1 VALUES(5, 6);
+      INSERT INTO t1 VALUES(7, 8);
+      INSERT INTO t1 VALUES(9, 10);
+    }
+    code2 { db2 close }
+    code1 { db close }
+    list [file size test.db-wal] [file size test.db-shm]
+  } [list [wal_file_size 4 1024] 32768]
+  do_test 3.3.1 {
+    code1 { sqlite3 db file:test.db?readonly_shm=1 }
+    sql1 { SELECT * FROM t1 }
+  } {a b c d e f g h 1 2 3 4 5 6 7 8 9 10}
+  do_test 3.3.2 {
+    code2 { sqlite3 db2 test.db }
+    sql2 { 
+      PRAGMA wal_checkpoint; 
+      DELETE FROM t1;
+      INSERT INTO t1 VALUES('i', 'ii');
+    }
+    code2 { db2 close }
+    list [file size test.db-wal] [file size test.db-shm]
+  } [list [wal_file_size 4 1024] 32768]
+  do_test 3.3.3 {
+    sql1 { SELECT * FROM t1 }
+  } {i ii}
+
 }
 
 finish_test