Index: ext/fts3/fts3.c
==================================================================
--- ext/fts3/fts3.c
+++ ext/fts3/fts3.c
@@ -4335,13 +4335,14 @@
   
       aPoslist = pExpr->pRight->pPhrase->doclist.pList;
       nToken = pExpr->pRight->pPhrase->nToken;
       for(p=pExpr->pLeft; p && res; p=p->pLeft){
         int nNear;
+        Fts3Phrase *pPhrase;
         assert( p->pParent && p->pParent->pLeft==p );
         nNear = p->pParent->nNear;
-        Fts3Phrase *pPhrase = (
+        pPhrase = (
             p->eType==FTSQUERY_NEAR ? p->pRight->pPhrase : p->pPhrase
         );
         res = fts3EvalNearTrim(nNear, aTmp, &aPoslist, &nToken, pPhrase);
       }
     }

Index: ext/rtree/rtree.c
==================================================================
--- ext/rtree/rtree.c
+++ ext/rtree/rtree.c
@@ -1570,10 +1570,11 @@
 
     float fMinGrowth = 0.0;
     float fMinArea = 0.0;
 #if VARIANT_RSTARTREE_CHOOSESUBTREE
     float fMinOverlap = 0.0;
+    float overlap;
 #endif
 
     int nCell = NCELL(pNode);
     RtreeCell cell;
     RtreeNode *pChild;
@@ -1602,18 +1603,19 @@
     */
     for(iCell=0; iCell<nCell; iCell++){
       int bBest = 0;
       float growth;
       float area;
-      float overlap = 0.0;
       nodeGetCell(pRtree, pNode, iCell, &cell);
       growth = cellGrowth(pRtree, &cell, pCell);
       area = cellArea(pRtree, &cell);
 
 #if VARIANT_RSTARTREE_CHOOSESUBTREE
       if( ii==(pRtree->iDepth-1) ){
         overlap = cellOverlapEnlargement(pRtree,&cell,pCell,aCell,nCell,iCell);
+      }else{
+        overlap = 0.0;
       }
       if( (iCell==0) 
        || (overlap<fMinOverlap) 
        || (overlap==fMinOverlap && growth<fMinGrowth)
        || (overlap==fMinOverlap && growth==fMinGrowth && area<fMinArea)

Index: src/backup.c
==================================================================
--- src/backup.c
+++ src/backup.c
@@ -541,18 +541,18 @@
 /*
 ** Release all resources associated with an sqlite3_backup* handle.
 */
 int sqlite3_backup_finish(sqlite3_backup *p){
   sqlite3_backup **pp;                 /* Ptr to head of pagers backup list */
-  sqlite3_mutex *mutex;                /* Mutex to protect source database */
+  MUTEX_LOGIC( sqlite3_mutex *mutex; ) /* Mutex to protect source database */
   int rc;                              /* Value to return */
 
   /* Enter the mutexes */
   if( p==0 ) return SQLITE_OK;
   sqlite3_mutex_enter(p->pSrcDb->mutex);
   sqlite3BtreeEnter(p->pSrc);
-  mutex = p->pSrcDb->mutex;
+  MUTEX_LOGIC( mutex = p->pSrcDb->mutex; )
   if( p->pDestDb ){
     sqlite3_mutex_enter(p->pDestDb->mutex);
   }
 
   /* Detach this backup from the source pager. */

Index: src/btree.c
==================================================================
--- src/btree.c
+++ src/btree.c
@@ -1764,21 +1764,23 @@
   */
   if( isMemdb==0 && isTempDb==0 ){
     if( vfsFlags & SQLITE_OPEN_SHAREDCACHE ){
       int nFullPathname = pVfs->mxPathname+1;
       char *zFullPathname = sqlite3Malloc(nFullPathname);
-      sqlite3_mutex *mutexShared;
+      MUTEX_LOGIC( sqlite3_mutex *mutexShared; )
       p->sharable = 1;
       if( !zFullPathname ){
         sqlite3_free(p);
         return SQLITE_NOMEM;
       }
       sqlite3OsFullPathname(pVfs, zFilename, nFullPathname, zFullPathname);
+#if SQLITE_THREADSAFE
       mutexOpen = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_OPEN);
       sqlite3_mutex_enter(mutexOpen);
       mutexShared = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
       sqlite3_mutex_enter(mutexShared);
+#endif
       for(pBt=GLOBAL(BtShared*,sqlite3SharedCacheList); pBt; pBt=pBt->pNext){
         assert( pBt->nRef>0 );
         if( 0==strcmp(zFullPathname, sqlite3PagerFilename(pBt->pPager))
                  && sqlite3PagerVfs(pBt->pPager)==pVfs ){
           int iDb;
@@ -1880,13 +1882,13 @@
    
 #if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
     /* Add the new BtShared object to the linked list sharable BtShareds.
     */
     if( p->sharable ){
-      sqlite3_mutex *mutexShared;
+      MUTEX_LOGIC( sqlite3_mutex *mutexShared; )
       pBt->nRef = 1;
-      mutexShared = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
+      MUTEX_LOGIC( mutexShared = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);)
       if( SQLITE_THREADSAFE && sqlite3GlobalConfig.bCoreMutex ){
         pBt->mutex = sqlite3MutexAlloc(SQLITE_MUTEX_FAST);
         if( pBt->mutex==0 ){
           rc = SQLITE_NOMEM;
           db->mallocFailed = 0;
@@ -1964,16 +1966,16 @@
 ** true if the BtShared.nRef counter reaches zero and return
 ** false if it is still positive.
 */
 static int removeFromSharingList(BtShared *pBt){
 #ifndef SQLITE_OMIT_SHARED_CACHE
-  sqlite3_mutex *pMaster;
+  MUTEX_LOGIC( sqlite3_mutex *pMaster; )
   BtShared *pList;
   int removed = 0;
 
   assert( sqlite3_mutex_notheld(pBt->mutex) );
-  pMaster = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
+  MUTEX_LOGIC( pMaster = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER); )
   sqlite3_mutex_enter(pMaster);
   pBt->nRef--;
   if( pBt->nRef<=0 ){
     if( GLOBAL(BtShared*,sqlite3SharedCacheList)==pBt ){
       GLOBAL(BtShared*,sqlite3SharedCacheList) = pBt->pNext;

Index: src/lempar.c
==================================================================
--- src/lempar.c
+++ src/lempar.c
@@ -714,11 +714,13 @@
   ParseTOKENTYPE yyminor       /* The value for the token */
   ParseARG_PDECL               /* Optional %extra_argument parameter */
 ){
   YYMINORTYPE yyminorunion;
   int yyact;            /* The parser action. */
+#if !defined(YYERRORSYMBOL) && !defined(YYNOERRORRECOVERY)
   int yyendofinput;     /* True if we are at the end of input */
+#endif
 #ifdef YYERRORSYMBOL
   int yyerrorhit = 0;   /* True if yymajor has invoked an error */
 #endif
   yyParser *yypParser;  /* The parser */
 
@@ -737,11 +739,13 @@
     yypParser->yyerrcnt = -1;
     yypParser->yystack[0].stateno = 0;
     yypParser->yystack[0].major = 0;
   }
   yyminorunion.yy0 = yyminor;
+#if !defined(YYERRORSYMBOL) && !defined(YYNOERRORRECOVERY)
   yyendofinput = (yymajor==0);
+#endif
   ParseARG_STORE;
 
 #ifndef NDEBUG
   if( yyTraceFILE ){
     fprintf(yyTraceFILE,"%sInput %s\n",yyTracePrompt,yyTokenName[yymajor]);
@@ -749,11 +753,10 @@
 #endif
 
   do{
     yyact = yy_find_shift_action(yypParser,(YYCODETYPE)yymajor);
     if( yyact<YYNSTATE ){
-      assert( !yyendofinput );  /* Impossible to shift the $ token */
       yy_shift(yypParser,yyact,yymajor,&yyminorunion);
       yypParser->yyerrcnt--;
       yymajor = YYNOCODE;
     }else if( yyact < YYNSTATE + YYNRULE ){
       yy_reduce(yypParser,yyact-YYNSTATE);

Index: src/main.c
==================================================================
--- src/main.c
+++ src/main.c
@@ -104,11 +104,11 @@
 **
 **    *  Recursive calls to this routine from thread X return immediately
 **       without blocking.
 */
 int sqlite3_initialize(void){
-  sqlite3_mutex *pMaster;                      /* The main static mutex */
+  MUTEX_LOGIC( sqlite3_mutex *pMaster; )       /* The main static mutex */
   int rc;                                      /* Result code */
 
 #ifdef SQLITE_OMIT_WSD
   rc = sqlite3_wsd_init(4096, 24);
   if( rc!=SQLITE_OK ){
@@ -138,11 +138,11 @@
   ** This operation is protected by the STATIC_MASTER mutex.  Note that
   ** MutexAlloc() is called for a static mutex prior to initializing the
   ** malloc subsystem - this implies that the allocation of a static
   ** mutex must not require support from the malloc subsystem.
   */
-  pMaster = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
+  MUTEX_LOGIC( pMaster = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER); )
   sqlite3_mutex_enter(pMaster);
   sqlite3GlobalConfig.isMutexInit = 1;
   if( !sqlite3GlobalConfig.isMallocInit ){
     rc = sqlite3MallocInit();
   }

Index: src/mutex.h
==================================================================
--- src/mutex.h
+++ src/mutex.h
@@ -58,14 +58,17 @@
 /*
 ** If this is a no-op implementation, implement everything as macros.
 */
 #define sqlite3_mutex_alloc(X)    ((sqlite3_mutex*)8)
 #define sqlite3_mutex_free(X)
-#define sqlite3_mutex_enter(X)
+#define sqlite3_mutex_enter(X)    
 #define sqlite3_mutex_try(X)      SQLITE_OK
-#define sqlite3_mutex_leave(X)
+#define sqlite3_mutex_leave(X)    
 #define sqlite3_mutex_held(X)     ((void)(X),1)
 #define sqlite3_mutex_notheld(X)  ((void)(X),1)
 #define sqlite3MutexAlloc(X)      ((sqlite3_mutex*)8)
 #define sqlite3MutexInit()        SQLITE_OK
 #define sqlite3MutexEnd()
+#define MUTEX_LOGIC(X)
+#else
+#define MUTEX_LOGIC(X)            X
 #endif /* defined(SQLITE_MUTEX_OMIT) */

Index: src/os.c
==================================================================
--- src/os.c
+++ src/os.c
@@ -295,16 +295,16 @@
 ** Register a VFS with the system.  It is harmless to register the same
 ** VFS multiple times.  The new VFS becomes the default if makeDflt is
 ** true.
 */
 int sqlite3_vfs_register(sqlite3_vfs *pVfs, int makeDflt){
-  sqlite3_mutex *mutex = 0;
+  MUTEX_LOGIC(sqlite3_mutex *mutex;)
 #ifndef SQLITE_OMIT_AUTOINIT
   int rc = sqlite3_initialize();
   if( rc ) return rc;
 #endif
-  mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
+  MUTEX_LOGIC( mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER); )
   sqlite3_mutex_enter(mutex);
   vfsUnlink(pVfs);
   if( makeDflt || vfsList==0 ){
     pVfs->pNext = vfsList;
     vfsList = pVfs;

Index: src/os_unix.c
==================================================================
--- src/os_unix.c
+++ src/os_unix.c
@@ -526,11 +526,11 @@
   return sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
 }
 #endif
 
 
-#ifdef SQLITE_DEBUG
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
 /*
 ** Helper function for printing out trace information from debugging
 ** binaries. This returns the string represetation of the supplied
 ** integer lock-type.
 */

Index: src/where.c
==================================================================
--- src/where.c
+++ src/where.c
@@ -2474,11 +2474,10 @@
   assert( roundUp==0 || roundUp==1 );
   assert( pIdx->nSample>0 );
   if( pVal==0 ) return SQLITE_ERROR;
   n = pIdx->aiRowEst[0];
   aSample = pIdx->aSample;
-  i = 0;
   eType = sqlite3_value_type(pVal);
 
   if( eType==SQLITE_INTEGER ){
     v = sqlite3_value_int64(pVal);
     r = (i64)v;

Index: test/tkt3793.test
==================================================================
--- test/tkt3793.test
+++ test/tkt3793.test
@@ -98,20 +98,22 @@
 # associated with [db1]. 
 #
 # Note: Before the bug was fixed, if [db2] was opened with the "-fullmutex 1"
 # option, then this test case would cause an assert() to fail.
 #
-set ::busyconnection db1
-db1 eval {SELECT * FROM t2 ORDER BY a LIMIT 20} {
-  do_test tkt3793-2.[incr x] { set ::busyconnection } db1
-  set ::busyconnection db2
-
-  db2 eval { SELECT count(*) FROM t2 }
-  do_test tkt3793-2.[incr x] { set ::busyconnection } db2
-  set ::busyconnection db1
-}
-
+ifcapable threadsafe {
+  set ::busyconnection db1
+  db1 eval {SELECT * FROM t2 ORDER BY a LIMIT 20} {
+    do_test tkt3793-2.[incr x] { set ::busyconnection } db1
+    set ::busyconnection db2
+  
+    db2 eval { SELECT count(*) FROM t2 }
+    do_test tkt3793-2.[incr x] { set ::busyconnection } db2
+    set ::busyconnection db1
+  }
+}
+  
 do_test tkt3793-3 {
   db1 close
   db2 close
 } {}
 

ADDED   tool/warnings-clang.sh
Index: tool/warnings-clang.sh
==================================================================
--- /dev/null
+++ tool/warnings-clang.sh
@@ -0,0 +1,13 @@
+#/bin/sh
+#
+# Run this script in a directory with a working makefile to check for 
+# compiler warnings in SQLite.
+#
+rm -f sqlite3.c
+make sqlite3.c
+echo '************* FTS4 and RTREE ****************'
+scan-build gcc -c -DHAVE_STDINT_H -DSQLITE_ENABLE_FTS4 -DSQLITE_ENABLE_RTREE \
+      -DSQLITE_DEBUG sqlite3.c 2>&1 | grep -v 'ANALYZE:'
+echo '********** ENABLE_STAT3. THREADSAFE=0 *******'
+scan-build gcc -c -DSQLITE_ENABLE_STAT3 -DSQLITE_THREADSAFE=0 \
+      -DSQLITE_DEBUG sqlite3.c 2>&1 | grep -v 'ANALYZE:'