Index: src/wal.c
==================================================================
--- src/wal.c
+++ src/wal.c
@@ -2197,11 +2197,12 @@
   /* Take WAL_READ_LOCK(0). This has the effect of preventing any
   ** live clients from running a checkpoint, but does not stop them
   ** from running recovery.  */
   rc = walLockShared(pWal, WAL_READ_LOCK(0));
   if( rc!=SQLITE_OK ){
-    return (rc==SQLITE_BUSY ? WAL_RETRY : rc);
+    if( rc==SQLITE_BUSY ) rc = WAL_RETRY;
+    goto begin_unlocked_out;
   }
   pWal->readLock = 0;
 
   /* Try to map the *-shm file again. If it succeeds this time, then 
   ** a non-readonly_shm connection has already connected to the database.
@@ -2221,18 +2222,22 @@
     goto begin_unlocked_out;
   }
 
   memcpy(&pWal->hdr, (void*)walIndexHdr(pWal), sizeof(WalIndexHdr));
   rc = sqlite3OsFileSize(pWal->pWalFd, &szWal);
-  if( rc!=SQLITE_OK || (szWal<WAL_HDRSIZE && pWal->hdr.mxFrame==0) ){
+  if( rc!=SQLITE_OK ){
+    goto begin_unlocked_out;
+  }
+  if( szWal<WAL_HDRSIZE ){
     /* If the wal file is too small to contain a wal-header and the
     ** wal-index header has mxFrame==0, then it must be safe to proceed
     ** reading the database file only. However, the page cache cannot
     ** be trusted, as a read/write connection may have connected, written
     ** the db, run a checkpoint, truncated the wal file and disconnected
     ** since this client's last read transaction.  */
     *pChanged = 1;
+    rc = (pWal->hdr.mxFrame==0 ? SQLITE_OK : WAL_RETRY);
     goto begin_unlocked_out;
   }
 
   /* Check the salt keys at the start of the wal file still match. */
   rc = sqlite3OsRead(pWal->pWalFd, aBuf, WAL_HDRSIZE, 0);
@@ -2266,20 +2271,11 @@
     u32 pgno;                   /* Database page number for frame */
     u32 nTruncate;              /* dbsize field from frame header */
 
     /* Read and decode the next log frame. */
     rc = sqlite3OsRead(pWal->pWalFd, aFrame, szFrame, iOffset);
-    if( rc!=SQLITE_OK ){
-      if( rc==SQLITE_IOERR_SHORT_READ ){
-        /* If this branch is taken, some other client has truncated the
-        ** *-wal file since the call to sqlite3OsFileSize() above. This
-        ** indicates that a read-write client has connected to the system.
-        ** So retry opening this read transaction.  */
-        rc = WAL_RETRY;
-      }
-      break;
-    }
+    if( rc!=SQLITE_OK ) break;
     if( !walDecodeFrame(pWal, &pgno, &nTruncate, aData, aFrame) ) break;
 
     /* 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.  */

Index: test/walro2.test
==================================================================
--- test/walro2.test
+++ test/walro2.test
@@ -193,9 +193,149 @@
     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}
+
+  #-----------------------------------------------------------------------
+  #
+  #
+  catch { code1 { db close } }
+  catch { code2 { db2 close } }
+  catch { code3 { db3 close } }
+
+  do_test 4.0 {
+    code1 { forcedelete test.db }
+    code1 { sqlite3 db test.db }
+    sql1 {
+      PRAGMA journal_mode = wal;
+      CREATE TABLE t1(x);
+      INSERT INTO t1 VALUES('hello');
+      INSERT INTO t1 VALUES('world');
+    }
+
+    forcecopy test.db test.db2
+    forcecopy test.db-wal test.db2-wal
+    forcecopy test.db-shm test.db2-shm
+    
+    code1 { db close }
+  } {}
+
+  do_test 4.1.1 {
+    code2 { sqlite3 db2 file:test.db2?readonly_shm=1 }
+    sql2 { SELECT * FROM t1 }
+  } {hello world}
+
+  do_test 4.1.2 {
+    code3 { sqlite3 db3 test.db2 }
+    sql3 {
+      INSERT INTO t1 VALUES('!');
+      PRAGMA wal_checkpoint = truncate;
+    }
+    code3 { db3 close }
+  } {}
+  do_test 4.1.3 {
+    sql2 { SELECT * FROM t1 }
+  } {hello world !}
+
+  catch { code1 { db close } }
+  catch { code2 { db2 close } }
+  catch { code3 { db3 close } }
+
+  do_test 4.2.1 {
+    code1 { sqlite3 db test.db }
+    sql1 {
+      INSERT INTO t1 VALUES('!');
+      INSERT INTO t1 VALUES('!');
+
+      PRAGMA cache_size = 10;
+      CREATE TABLE t2(x);
+
+      BEGIN;
+        WITH s(i) AS (
+          SELECT 1 UNION ALL SELECT i+1 FROM s WHERE i<500
+          )
+        INSERT INTO t2 SELECT randomblob(500) FROM s;
+        SELECT count(*) FROM t2;
+    } 
+  } {500}
+  do_test 4.2.2 {
+    file size test.db-wal
+  } {461152}
+  do_test 4.2.4 {
+    forcecopy test.db test.db2
+    forcecopy test.db-wal test.db2-wal
+    forcecopy test.db-shm test.db2-shm
+
+    code2 { sqlite3 db2 file:test.db2?readonly_shm=1 }
+    sql2 {
+      SELECT * FROM t1;
+      SELECT count(*) FROM t2;
+    }
+  } {hello world ! ! 0}
+
+  #-----------------------------------------------------------------------
+  #
+  #
+  catch { code1 { db close } }
+  catch { code2 { db2 close } }
+  catch { code3 { db3 close } }
+
+  do_test 5.0 {
+    code1 { forcedelete test.db }
+    code1 { sqlite3 db test.db }
+    sql1 {
+      PRAGMA journal_mode = wal;
+      CREATE TABLE t1(x);
+      INSERT INTO t1 VALUES('hello');
+      INSERT INTO t1 VALUES('world');
+      INSERT INTO t1 VALUES('!');
+      INSERT INTO t1 VALUES('world');
+      INSERT INTO t1 VALUES('hello');
+    }
+
+    forcecopy test.db test.db2
+    forcecopy test.db-wal test.db2-wal
+    forcecopy test.db-shm test.db2-shm
+    
+    code1 { db close }
+  } {}
+
+  do_test 5.1 {
+    code2 { sqlite3 db2 file:test.db2?readonly_shm=1 }
+    sql2 {
+      SELECT * FROM t1;
+    }
+  } {hello world ! world hello}
+
+  do_test 5.2 {
+    code1 {
+      proc handle_read {op args} {
+        if {$op=="xRead" && [file tail [lindex $args 0]]=="test.db2-wal"} {
+          set ::res2 [sql2 { SELECT * FROM t1 }]
+        }
+        puts "$msg xRead $args"
+        return "SQLITE_OK"
+      }
+      testvfs tvfs -fullshm 1
+
+      sqlite3 db file:test.db2?vfs=tvfs
+      db eval { SELECT * FROM sqlite_master }
+
+      tvfs filter xRead
+      tvfs script handle_read
+    }
+    sql1 {
+      PRAGMA wal_checkpoint = truncate;
+    }
+    code1 { set ::res2 }
+  } {hello world ! world hello}
+
+  do_test 5.3 {
+    code1 { db close }
+    code1 { tvfs delete }
+  } {}
+
 
 }
 
 finish_test