Automatically deallocate thread-specific data when it is no longer

being used.  Ticket #1601.  Also implemented the suggestion of
ticket #1603. Memory management is now off by default at compile-time.
The sqlite3_enable_memory_management() API has been removed. (CVS 2919)

FossilOrigin-Name: 5d9c6aa964305c3f36741ff0058da5b5f3ce0d24

31 files changed, 332 insertions, 297 deletions

diff --git a/manifest b/manifest
index 73f57727b..d84b1927c 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Ensure\sthe\sdatabase\sattached\sas\spart\sof\sVACUUM\scan\sbe\sdetached\ssuccessfully\safter\sa\smalloc()\sfailure.\s(CVS\s2918)
-D 2006-01-11T16:10:20
+C Automatically\sdeallocate\sthread-specific\sdata\swhen\sit\sis\sno\slonger\nbeing\sused.\s\sTicket\s#1601.\s\sAlso\simplemented\sthe\ssuggestion\sof\nticket\s#1603.\sMemory\smanagement\sis\snow\soff\sby\sdefault\sat\scompile-time.\nThe\ssqlite3_enable_memory_management()\sAPI\shas\sbeen\sremoved.\s(CVS\s2919)
+D 2006-01-11T21:41:21
 F Makefile.in ab3ffd8d469cef4477257169b82810030a6bb967
 F Makefile.linux-gcc aee18d8a05546dcf1888bd4547e442008a49a092
 F README 9c4e2d6706bdcc3efdd773ce752a8cdab4f90028
@@ -28,52 +28,52 @@ F publish.sh ed0aba4ffdfadb36597d03ce8efdae96efc038cb
 F spec.template b2f6c4e488cbc3b993a57deba22cbc36203c4da3
 F sqlite.pc.in 30552343140c53304c2a658c080fbe810cd09ca2
 F sqlite3.1 6be1ad09113570e1fc8dcaff84c9b0b337db5ffc
-F sqlite3.def ccf06c86eaa2c123271db41352d2b3c9e4ec42a5
+F sqlite3.def 99ac9728b515bb49d1af29153d64c8e7aad7bcc3
 F sqlite3.pc.in 985b9bf34192a549d7d370e0f0b6b34a4f61369a
-F src/alter.c d0dd079b9ef0d551ff4a4ce09ee270c07b307bbb
+F src/alter.c 4139c8f1d0f12b1759e767b1d09dd594e2b5ac1d
 F src/analyze.c 7d2b7ab9a9c2fd6e55700f69064dfdd3e36d7a8a
-F src/attach.c fb93d00ab7cb392579ea7db0a1247196d7220788
+F src/attach.c d4b9d8bd71d72409720946355be41cafb6c09079
 F src/auth.c cdec356a5cd8b217c346f816c5912221537fe87f
-F src/btree.c e1f6b2e22484d754b79b7c9b43e7a09af259f0f6
+F src/btree.c b407273cb22f39606acc27b8a4a74c6272c7a9d2
 F src/btree.h 5663c4f43e8521546ccebc8fc95acb013b8f3184
-F src/build.c c7847f299ded7fec899bfda74d4d31ba9f80aa75
-F src/callback.c 51fe813309f7cf69d3d19a2e7be2103130186efd
+F src/build.c 652a3932292c2b8d1900219f537f1b5e21490afa
+F src/callback.c ba3e6cc7a6beb562e7a66f92e26fabcb21aab1e2
 F src/complete.c df1681cef40dec33a286006981845f87b194e7a4
 F src/date.c a927bdbb51296ac398d2f667086a7072c099e5ab
-F src/delete.c b242a0d9462d2b7054e38c5250bdbe94d6772a8e
+F src/delete.c c7bd5708a629585e073ce34cf3b1fcb52c2fef38
 F src/experimental.c 50c1e3b34f752f4ac10c36f287db095c2b61766d
-F src/expr.c b90fa835a2216edd6808b4bb5da6bbf3b8ee29b9
+F src/expr.c 3b6acdb4e254027fe72ce70054ea6b71c7d423a3
 F src/func.c e013c3b6c607c6a1654f5260eab59f5609a5ce4a
 F src/hash.c 8747cf51d12de46512880dfcf1b68b4e24072863
 F src/hash.h 1b0c445e1c89ff2aaad9b4605ba61375af001e84
-F src/insert.c 337785137430a012ff0f1c181d4a4d55d2a942d3
-F src/legacy.c f651ccd3700f99fa05766ac53506bf9a0694761b
-F src/main.c 3fe4b606db7d269d7a57c7b51ab3d9ff488e4b98
+F src/insert.c a5595cf8d1d8ba087b676a63f1f7277ea44b5ac1
+F src/legacy.c 9bf7ee1b63c99aac6669533986a5240b16101458
+F src/main.c 39d073fb1f95f874ee0c98366e99005cf14742dd
 F src/md5.c c5fdfa5c2593eaee2e32a5ce6c6927c986eaf217
 F src/os.c 1d1a61cdf150e9f9520a3bc787c8465148ea2e78
-F src/os.h 8710c0068f3386a73a37f8ad242b92c7580464df
+F src/os.h 9debc3d3ca4cdafde222a0ea74a4c8415aef4f22
 F src/os_common.h 78bcc34dded9b625b3c16d072b7e5b76d075a674
 F src/os_test.c 49833426101f99aee4bb5f6a44b7c4b2029fda1c
 F src/os_test.h 903c93554c23d88f34f667f1979e4a1cee792af3
-F src/os_unix.c 8943febbedc79649d21ec1ed14de14ad8214c899
+F src/os_unix.c 557a21c563496a1ccef32b1d57376d135884eac5
 F src/os_unix.h 5768d56d28240d3fe4537fac08cc85e4fb52279e
-F src/os_win.c 8ef250a0965a55dbcd8ef785e03f9f3292e6ade2
+F src/os_win.c b67dd34bf1ae796851910a229bd94026b42d942f
 F src/os_win.h 41a946bea10f61c158ce8645e7646b29d44f122b
-F src/pager.c 0a59a320b0da6b22d2dd4411d16e300ff1b947c8
+F src/pager.c a96b9c43664670576e41eac699277c7862d604d8
 F src/pager.h e0acb095b3ad0bca48f2ab00c87346665643f64f
 F src/parse.y 83df51fea35f68f7e07384d75dce83d1ed30434c
 F src/pragma.c d439d257c1bcacbc09d38820ac578749df900562
-F src/prepare.c 65b166b806e4af6e0035acdd5f6a24e2ec02b66d
+F src/prepare.c 60c1f5e3d2901d651f8ca9f06e39e2ff3f335844
 F src/printf.c f47a2f4b5387cd2ebb12e9117a1a5d6bd9a2b812
 F src/random.c d40f8d356cecbd351ccfab6eaedd7ec1b54f5261
-F src/select.c 579cfdd250c5598de7c867134f7d35a2099b1dcc
+F src/select.c 7b19d350cb2a18ae4a59d6b87049aa2ce9c671ae
 F src/server.c 519e308651e30102dd3d1f4053ac64c14267e44c
 F src/shell.c 66b073375efbdee19045e7e0cd38b85f9aff71da
-F src/sqlite.h.in 821b93f918d126c54d9a91fc928434945655edc3
-F src/sqliteInt.h 829f8c22767ceaed717042087e7fb4d599a3c44c
+F src/sqlite.h.in 4320cff369e37897d2839d526c2b8917a2756d60
+F src/sqliteInt.h bd3fba6d7163ef402b5633191ee5d7de5b7f6e80
 F src/table.c 486dcfce532685b53b5a2b5da8bba0ded6fb2316
 F src/tclsqlite.c d650bea0248fc0a310ddc2cb94273a3a5021fddf
-F src/test1.c b2923fd22ec44cf05d6d51dc460e8ed8e0d5f241
+F src/test1.c d38c9f4da2136c5e1747517d7b564ba88a91fbee
 F src/test2.c ca74a1d8aeb7d9606e8f6b762c5daf85c1a3f92b
 F src/test3.c 9742aa146eb750cab81c1d5605286c3a0eb88054
 F src/test4.c a8fd681e139e1c61f22a77d07fc3a99cb28fff3f
@@ -81,20 +81,20 @@ F src/test5.c 7162f8526affb771c4ed256826eee7bb9eca265f
 F src/test6.c 74d91b487c68154156eded457925d96aa2a3fdbb
 F src/test7.c bfe36c62cae189509660acfeeb891ffb9da8ef0c
 F src/test_async.c 6776f5027ca6378c116ff5ccc2fe41b908e33772
-F src/tokenize.c 196486012c871cdcad6cc84a820cc988603f1b9d
-F src/trigger.c 883b5f3b97137fbe417e3337c3fa20ac8e9c1ae5
-F src/update.c cd8ad5bb1a29f2056347481308fca4a59f2f4764
+F src/tokenize.c b75d24cbb419eef9ae7be286dd66723a2ee49f4f
+F src/trigger.c 694b247476d2fc0dce003af564f79e8752fc1158
+F src/update.c 261d75c702c2852d1a64274d7c414485e6f2d177
 F src/utf.c b7bffac4260177ae7f83c01d025fe0f5ed70ce71
-F src/util.c 3616a0a1f1b89cfb376240c75434431b8028681e
+F src/util.c 8a147f96099ce716e4ee750142a8f53f1aed3286
 F src/vacuum.c cd56995ecea281b3ac306ef88128ebc8a2117f84
-F src/vdbe.c aa4360d28c4476e435c84e92ad3fbd65a8944156
+F src/vdbe.c db592ade9a0e381f5e6a7a35a67e81c2722480b5
 F src/vdbe.h 8729a4ee16ff9aeab2af9667df3cf300ff978e13
 F src/vdbeInt.h 5451cf71f229e366ac543607c0a17f36e5737ea9
-F src/vdbeapi.c 6d20e92de62b90ae27aeea3a7b18653734b0b1cb
-F src/vdbeaux.c e4b8f492e41e3b8ecee8f66045e897dae92d1356
+F src/vdbeapi.c afd3837cea0dec93dcb4724d073c84fa0da68e23
+F src/vdbeaux.c fca3a799a1e9d5b595a4e5d140f182601258287a
 F src/vdbefifo.c 9efb94c8c3f4c979ebd0028219483f88e57584f5
-F src/vdbemem.c 2ada7cae76da9c840cd0d3c01d2b3987d97141c6
-F src/where.c 4fecfccf8f35ec7b325d666f0cd2fb016a53da43
+F src/vdbemem.c 66e05857c3bd52436161d6bf96a95725f03225a5
+F src/where.c a8ba7f4aa2f38166e9f89ecc5dafbdbf41942031
 F tclinstaller.tcl 046e3624671962dc50f0481d7c25b38ef803eb42
 F test/all.test a23fcbbf1f53515bde840d78732a6d94c673b327
 F test/alter.test b94b640063e725d062b2997bd2810ac39195c718
@@ -340,7 +340,7 @@ F www/tclsqlite.tcl bb0d1357328a42b1993d78573e587c6dcbc964b9
 F www/vdbe.tcl 87a31ace769f20d3627a64fa1fade7fed47b90d0
 F www/version3.tcl a99cf5f6d8bd4d5537584a2b342f0fb9fa601d8b
 F www/whentouse.tcl 97e2b5cd296f7d8057e11f44427dea8a4c2db513
-P 3970eb875d1830d35b3a70a7583a8ab6b238cad6
-R 5d634fd31ace904b5b4a4cd1fc441144
-U danielk1977
-Z 11d0cd52f201ef748e551ed33dbe55f7
+P 8c26893c65574b0667bb84bde3ca49751079cc8d
+R a464a0f33259fc5b6aae2e3199e401a7
+U drh
+Z 7760f8b5862256854e201380c09a40e6
diff --git a/manifest.uuid b/manifest.uuid
index 9ed2e2044..527e175ef 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-8c26893c65574b0667bb84bde3ca49751079cc8d
\ No newline at end of file
+5d9c6aa964305c3f36741ff0058da5b5f3ce0d24
\ No newline at end of file
diff --git a/sqlite3.def b/sqlite3.def
index 2921494b9..41dae4260 100644
--- a/sqlite3.def
+++ b/sqlite3.def
@@ -84,6 +84,7 @@ sqlite3_set_auxdata
 sqlite3_snprintf
 sqlite3_soft_heap_limit
 sqlite3_step
+sqlite3_thread_cleanup
 sqlite3_total_changes
 sqlite3_trace
 sqlite3_transfer_bindings
diff --git a/src/alter.c b/src/alter.c
index c9fa9deed..f1809f4c8 100644
--- a/src/alter.c
+++ b/src/alter.c
@@ -12,7 +12,7 @@
 ** This file contains C code routines that used to generate VDBE code
 ** that implements the ALTER TABLE command.
 **
-** $Id: alter.c,v 1.15 2006/01/09 06:29:48 danielk1977 Exp $
+** $Id: alter.c,v 1.16 2006/01/11 21:41:21 drh Exp $
 */
 #include "sqliteInt.h"
 #include <ctype.h>
@@ -267,7 +267,7 @@ void sqlite3AlterRenameTable(
   char *zWhere = 0;         /* Where clause to locate temp triggers */
 #endif
   
-  if( sqlite3ThreadData()->mallocFailed ) goto exit_rename_table;
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ) goto exit_rename_table;
   assert( pSrc->nSrc==1 );
 
   pTab = sqlite3LocateTable(pParse, pSrc->a[0].zName, pSrc->a[0].zDatabase);
@@ -501,7 +501,7 @@ void sqlite3AlterBeginAddColumn(Parse *pParse, SrcList *pSrc){
 
   /* Look up the table being altered. */
   assert( pParse->pNewTable==0 );
-  if( sqlite3ThreadData()->mallocFailed ) goto exit_begin_add_column;
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ) goto exit_begin_add_column;
   pTab = sqlite3LocateTable(pParse, pSrc->a[0].zName, pSrc->a[0].zDatabase);
   if( !pTab ) goto exit_begin_add_column;
 
diff --git a/src/attach.c b/src/attach.c
index f1f1bbbd9..290596a95 100644
--- a/src/attach.c
+++ b/src/attach.c
@@ -11,7 +11,7 @@
 *************************************************************************
 ** This file contains code used to implement the ATTACH and DETACH commands.
 **
-** $Id: attach.c,v 1.45 2006/01/11 14:09:31 danielk1977 Exp $
+** $Id: attach.c,v 1.46 2006/01/11 21:41:22 drh Exp $
 */
 #include "sqliteInt.h"
 
@@ -272,7 +272,7 @@ static void codeAttach(
   sqlite3* db = pParse->db;
 
 #ifndef SQLITE_OMIT_AUTHORIZATION
-  assert( sqlite3ThreadData()->mallocFailed || pAuthArg );
+  assert( sqlite3ThreadDataReadOnly()->mallocFailed || pAuthArg );
   if( pAuthArg ){
     char *zAuthArg = sqlite3NameFromToken(&pAuthArg->span);
     if( !zAuthArg ){
@@ -303,7 +303,7 @@ static void codeAttach(
   sqlite3ExprCode(pParse, pDbname);
   sqlite3ExprCode(pParse, pKey);
 
-  assert(v || sqlite3ThreadData()->mallocFailed);
+  assert(v || sqlite3ThreadDataReadOnly()->mallocFailed);
   if( v ){
     sqlite3VdbeAddOp(v, OP_Function, 0, nFunc);
     pFunc = sqlite3FindFunction(db, zFunc, strlen(zFunc), nFunc, SQLITE_UTF8,0);
diff --git a/src/btree.c b/src/btree.c
index b1bd141ed..064b3d301 100644
--- a/src/btree.c
+++ b/src/btree.c
@@ -9,7 +9,7 @@
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
-** $Id: btree.c,v 1.290 2006/01/11 14:09:31 danielk1977 Exp $
+** $Id: btree.c,v 1.291 2006/01/11 21:41:22 drh Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** For a detailed discussion of BTrees, refer to
@@ -557,7 +557,7 @@ static int saveCursorPosition(BtCursor *pCur){
 */
 static int saveAllCursors(BtShared *pBt, Pgno iRoot, BtCursor *pExcept){
   BtCursor *p;
-  if( sqlite3ThreadData()->useSharedData ){
+  if( sqlite3ThreadDataReadOnly()->useSharedData ){
     for(p=pBt->pCursor; p; p=p->pNext){
       if( p!=pExcept && p->pgnoRoot==iRoot && p->eState==CURSOR_VALID ){
         int rc = saveCursorPosition(p);
@@ -584,7 +584,7 @@ static int saveAllCursors(BtShared *pBt, Pgno iRoot, BtCursor *pExcept){
 static int restoreCursorPosition(BtCursor *pCur, int doSeek){
   int rc = SQLITE_OK;
   if( pCur->eState==CURSOR_REQUIRESEEK ){
-    assert( sqlite3ThreadData()->useSharedData );
+    assert( sqlite3ThreadDataReadOnly()->useSharedData );
     if( doSeek ){
       rc = sqlite3BtreeMoveto(pCur, pCur->pKey, pCur->nKey, &pCur->skip);
     }else{
@@ -610,7 +610,7 @@ static int queryTableLock(Btree *p, Pgno iTab, u8 eLock){
   BtLock *pIter;
 
   /* This is a no-op if the shared-cache is not enabled */
-  if( 0==sqlite3ThreadData()->useSharedData ){
+  if( 0==sqlite3ThreadDataReadOnly()->useSharedData ){
     return SQLITE_OK;
   }
 
@@ -658,7 +658,7 @@ static int lockTable(Btree *p, Pgno iTable, u8 eLock){
   BtLock *pIter;
 
   /* This is a no-op if the shared-cache is not enabled */
-  if( 0==sqlite3ThreadData()->useSharedData ){
+  if( 0==sqlite3ThreadDataReadOnly()->useSharedData ){
     return SQLITE_OK;
   }
 
@@ -723,7 +723,7 @@ static void unlockAllTables(Btree *p){
   ** locks in the BtShared.pLock list, making this procedure a no-op. Assert
   ** that this is the case.
   */
-  assert( sqlite3ThreadData()->useSharedData || 0==*ppIter );
+  assert( sqlite3ThreadDataReadOnly()->useSharedData || 0==*ppIter );
 
   while( *ppIter ){
     BtLock *pLock = *ppIter;
@@ -1546,8 +1546,8 @@ int sqlite3BtreeOpen(
   int rc;
   int nReserve;
   unsigned char zDbHeader[100];
-#ifndef SQLITE_OMIT_SHARED_CACHE
-  ThreadData *pTsd = sqlite3ThreadData();
+#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
+  const ThreadData *pTsdro;
 #endif
 
   /* Set the variable isMemdb to true for an in-memory database, or 
@@ -1572,13 +1572,14 @@ int sqlite3BtreeOpen(
 
   /* Try to find an existing Btree structure opened on zFilename. */
 #if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
-  if( pTsd->useSharedData && zFilename && !isMemdb ){
+  pTsdro = sqlite3ThreadDataReadOnly();
+  if( pTsdro->useSharedData && zFilename && !isMemdb ){
     char *zFullPathname = sqlite3OsFullPathname(zFilename);
     if( !zFullPathname ){
       sqliteFree(p);
       return SQLITE_NOMEM;
     }
-    for(pBt=pTsd->pBtree; pBt; pBt=pBt->pNext){
+    for(pBt=pTsdro->pBtree; pBt; pBt=pBt->pNext){
       assert( pBt->nRef>0 );
       if( 0==strcmp(zFullPathname, sqlite3pager_filename(pBt->pPager)) ){
         p->pBt = pBt;
@@ -1660,9 +1661,9 @@ int sqlite3BtreeOpen(
 
 #ifndef SQLITE_OMIT_SHARED_CACHE
   /* Add the new btree to the linked list starting at ThreadData.pBtree */
-  if( pTsd->useSharedData && zFilename && !isMemdb ){
-    pBt->pNext = pTsd->pBtree;
-    pTsd->pBtree = pBt;
+  if( pTsdro->useSharedData && zFilename && !isMemdb ){
+    pBt->pNext = pTsdro->pBtree;
+    sqlite3ThreadData()->pBtree = pBt;
   }
 #endif
   pBt->nRef = 1;
@@ -1678,7 +1679,7 @@ int sqlite3BtreeClose(Btree *p){
   BtCursor *pCur;
 
 #ifndef SQLITE_OMIT_SHARED_CACHE
-  ThreadData *pTsd = sqlite3ThreadData();
+  ThreadData *pTsd;
 #endif
 
   /* Drop any table-locks */
@@ -1708,6 +1709,7 @@ int sqlite3BtreeClose(Btree *p){
   }
 
   /* Remove the shared-btree from the thread wide list */
+  pTsd = sqlite3ThreadData();
   if( pTsd->pBtree==pBt ){
     pTsd->pBtree = pBt->pNext;
   }else{
@@ -6500,7 +6502,12 @@ int sqlite3BtreeLockTable(Btree *p, int iTab, u8 isWriteLock){
   return rc;
 }
 
-#if defined(SQLITE_TEST) && !defined(NO_TCL)
+/*
+** The following debugging interface has to be in this file (rather
+** than in, for example, test1.c) so that it can get access to
+** the definition of BtShared.
+*/
+#if defined(SQLITE_TEST) && defined(TCLSH)
 #include <tcl.h>
 int sqlite3_shared_cache_report(
   void * clientData,
@@ -6508,7 +6515,7 @@ int sqlite3_shared_cache_report(
   int objc,
   Tcl_Obj *CONST objv[]
 ){
-  ThreadData *pTd = sqlite3ThreadData();
+  const ThreadData *pTd = sqlite3ThreadDataReadOnly();
   if( pTd->useSharedData ){
     BtShared *pBt;
     Tcl_Obj *pRet = Tcl_NewObj();
@@ -6522,4 +6529,3 @@ int sqlite3_shared_cache_report(
   return TCL_OK;
 }
 #endif
-
diff --git a/src/build.c b/src/build.c
index 65ce2e533..ee3991018 100644
--- a/src/build.c
+++ b/src/build.c
@@ -22,7 +22,7 @@
 **     COMMIT
 **     ROLLBACK
 **
-** $Id: build.c,v 1.376 2006/01/11 14:09:32 danielk1977 Exp $
+** $Id: build.c,v 1.377 2006/01/11 21:41:22 drh Exp $
 */
 #include "sqliteInt.h"
 #include <ctype.h>
@@ -66,9 +66,8 @@ void sqlite3TableLock(
   int i;
   int nBytes;
   TableLock *p;
-  ThreadData *pTsd = sqlite3ThreadData();
 
-  if( 0==pTsd->useSharedData || iDb<0 ){
+  if( 0==sqlite3ThreadDataReadOnly()->useSharedData || iDb<0 ){
     return;
   }
 
@@ -98,7 +97,7 @@ void sqlite3TableLock(
 static void codeTableLocks(Parse *pParse){
   int i;
   Vdbe *pVdbe; 
-  assert( sqlite3ThreadData()->useSharedData || pParse->nTableLock==0 );
+  assert( sqlite3ThreadDataReadOnly()->useSharedData || pParse->nTableLock==0 );
 
   if( 0==(pVdbe = sqlite3GetVdbe(pParse)) ){
     return;
@@ -131,7 +130,7 @@ void sqlite3FinishCoding(Parse *pParse){
   sqlite3 *db;
   Vdbe *v;
 
-  if( sqlite3ThreadData()->mallocFailed ) return;
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ) return;
   if( pParse->nested ) return;
   if( !pParse->pVdbe ){
     if( pParse->rc==SQLITE_OK && pParse->nErr ){
@@ -1363,7 +1362,7 @@ void sqlite3EndTable(
   int iDb;
 
   if( (pEnd==0 && pSelect==0) || 
-      pParse->nErr || sqlite3ThreadData()->mallocFailed ) {
+      pParse->nErr || sqlite3ThreadDataReadOnly()->mallocFailed ) {
     return;
   }
   p = pParse->pNewTable;
@@ -1600,7 +1599,7 @@ void sqlite3CreateView(
   */
   p->pSelect = sqlite3SelectDup(pSelect);
   sqlite3SelectDelete(pSelect);
-  if( sqlite3ThreadData()->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     return;
   }
   if( !pParse->db->init.busy ){
@@ -1842,7 +1841,9 @@ void sqlite3DropTable(Parse *pParse, SrcList *pName, int isView, int noErr){
   sqlite3 *db = pParse->db;
   int iDb;
 
-  if( pParse->nErr || sqlite3ThreadData()->mallocFailed ) goto exit_drop_table;
+  if( pParse->nErr || sqlite3ThreadDataReadOnly()->mallocFailed ){
+    goto exit_drop_table;
+  }
   assert( pName->nSrc==1 );
   pTab = sqlite3LocateTable(pParse, pName->a[0].zName, pName->a[0].zDatabase);
 
@@ -2201,7 +2202,7 @@ void sqlite3CreateIndex(
   int nExtra = 0;
   char *zExtra;
 
-  if( pParse->nErr || sqlite3ThreadData()->mallocFailed ){
+  if( pParse->nErr || sqlite3ThreadDataReadOnly()->mallocFailed ){
     goto exit_create_index;
   }
 
@@ -2355,7 +2356,7 @@ void sqlite3CreateIndex(
       nName + 1 +                  /* Index.zName      */
       nExtra                       /* Collation sequence names */
   );
-  if( sqlite3ThreadData()->mallocFailed ) goto exit_create_index;
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ) goto exit_create_index;
   pIndex->aiColumn = (int *)(&pIndex[1]);
   pIndex->aiRowEst = (int *)(&pIndex->aiColumn[nCol]);
   pIndex->azColl = (char **)(&pIndex->aiRowEst[nCol+1]);
@@ -2642,7 +2643,7 @@ void sqlite3DropIndex(Parse *pParse, SrcList *pName, int ifExists){
   sqlite3 *db = pParse->db;
   int iDb;
 
-  if( pParse->nErr || sqlite3ThreadData()->mallocFailed ){
+  if( pParse->nErr || sqlite3ThreadDataReadOnly()->mallocFailed ){
     goto exit_drop_index;
   }
   assert( pName->nSrc==1 );
@@ -2851,7 +2852,7 @@ SrcList *sqlite3SrcListAppend(SrcList *pList, Token *pTable, Token *pDatabase){
 void sqlite3SrcListAssignCursors(Parse *pParse, SrcList *pList){
   int i;
   struct SrcList_item *pItem;
-  assert(pList || sqlite3ThreadData()->mallocFailed);
+  assert(pList || sqlite3ThreadDataReadOnly()->mallocFailed);
   if( pList ){
     for(i=0, pItem=pList->a; i<pList->nSrc; i++, pItem++){
       if( pItem->iCursor>=0 ) break;
@@ -2900,7 +2901,7 @@ void sqlite3BeginTransaction(Parse *pParse, int type){
   int i;
 
   if( pParse==0 || (db=pParse->db)==0 || db->aDb[0].pBt==0 ) return;
-  if( pParse->nErr || sqlite3ThreadData()->mallocFailed ) return;
+  if( pParse->nErr || sqlite3ThreadDataReadOnly()->mallocFailed ) return;
   if( sqlite3AuthCheck(pParse, SQLITE_TRANSACTION, "BEGIN", 0, 0) ) return;
 
   v = sqlite3GetVdbe(pParse);
@@ -2921,7 +2922,7 @@ void sqlite3CommitTransaction(Parse *pParse){
   Vdbe *v;
 
   if( pParse==0 || (db=pParse->db)==0 || db->aDb[0].pBt==0 ) return;
-  if( pParse->nErr || sqlite3ThreadData()->mallocFailed ) return;
+  if( pParse->nErr || sqlite3ThreadDataReadOnly()->mallocFailed ) return;
   if( sqlite3AuthCheck(pParse, SQLITE_TRANSACTION, "COMMIT", 0, 0) ) return;
 
   v = sqlite3GetVdbe(pParse);
@@ -2938,7 +2939,7 @@ void sqlite3RollbackTransaction(Parse *pParse){
   Vdbe *v;
 
   if( pParse==0 || (db=pParse->db)==0 || db->aDb[0].pBt==0 ) return;
-  if( pParse->nErr || sqlite3ThreadData()->mallocFailed ) return;
+  if( pParse->nErr || sqlite3ThreadDataReadOnly()->mallocFailed ) return;
   if( sqlite3AuthCheck(pParse, SQLITE_TRANSACTION, "ROLLBACK", 0, 0) ) return;
 
   v = sqlite3GetVdbe(pParse);
@@ -3212,4 +3213,3 @@ KeyInfo *sqlite3IndexKeyinfo(Parse *pParse, Index *pIdx){
   }
   return pKey;
 }
-
diff --git a/src/callback.c b/src/callback.c
index a1bf57789..c63b588aa 100644
--- a/src/callback.c
+++ b/src/callback.c
@@ -13,7 +13,7 @@
 ** This file contains functions used to access the internal hash tables
 ** of user defined functions and collation sequences.
 **
-** $Id: callback.c,v 1.10 2006/01/10 17:58:23 danielk1977 Exp $
+** $Id: callback.c,v 1.11 2006/01/11 21:41:22 drh Exp $
 */
 
 #include "sqliteInt.h"
@@ -178,7 +178,8 @@ static CollSeq *findCollSeqEntry(
       ** return the pColl pointer to be deleted (because it wasn't added
       ** to the hash table).
       */
-      assert( !pDel || (sqlite3ThreadData()->mallocFailed && pDel==pColl) );
+      assert( !pDel ||
+              (sqlite3ThreadDataReadOnly()->mallocFailed && pDel==pColl) );
       sqliteFree(pDel);
     }
   }
diff --git a/src/delete.c b/src/delete.c
index c1bc52998..1c85c4777 100644
--- a/src/delete.c
+++ b/src/delete.c
@@ -12,7 +12,7 @@
 ** This file contains C code routines that are called by the parser
 ** in order to generate code for DELETE FROM statements.
 **
-** $Id: delete.c,v 1.117 2006/01/10 17:58:23 danielk1977 Exp $
+** $Id: delete.c,v 1.118 2006/01/11 21:41:22 drh Exp $
 */
 #include "sqliteInt.h"
 
@@ -108,7 +108,7 @@ void sqlite3DeleteFrom(
 #endif
 
   sContext.pParse = 0;
-  if( pParse->nErr || sqlite3ThreadData()->mallocFailed ){
+  if( pParse->nErr || sqlite3ThreadDataReadOnly()->mallocFailed ){
     goto delete_from_cleanup;
   }
   db = pParse->db;
diff --git a/src/expr.c b/src/expr.c
index fa7be8c35..108f69db0 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -12,7 +12,7 @@
 ** This file contains routines used for analyzing expressions and
 ** for generating VDBE code that evaluates expressions in SQLite.
 **
-** $Id: expr.c,v 1.247 2006/01/10 17:58:23 danielk1977 Exp $
+** $Id: expr.c,v 1.248 2006/01/11 21:41:22 drh Exp $
 */
 #include "sqliteInt.h"
 #include <ctype.h>
@@ -263,7 +263,7 @@ Expr *sqlite3ExprAnd(Expr *pLeft, Expr *pRight){
 void sqlite3ExprSpan(Expr *pExpr, Token *pLeft, Token *pRight){
   assert( pRight!=0 );
   assert( pLeft!=0 );
-  if( !sqlite3ThreadData()->mallocFailed && pRight->z && pLeft->z ){
+  if( !sqlite3ThreadDataReadOnly()->mallocFailed && pRight->z && pLeft->z ){
     assert( pLeft->dyn==0 || pLeft->z[pLeft->n]==0 );
     if( pLeft->dyn==0 && pRight->dyn==0 ){
       pExpr->span.z = pLeft->z;
@@ -358,7 +358,7 @@ void sqlite3ExprAssignVarNumber(Parse *pParse, Expr *pExpr){
         sqlite3ReallocOrFree((void**)&pParse->apVarExpr,
                        pParse->nVarExprAlloc*sizeof(pParse->apVarExpr[0]) );
       }
-      if( !sqlite3ThreadData()->mallocFailed ){
+      if( !sqlite3ThreadDataReadOnly()->mallocFailed ){
         assert( pParse->apVarExpr!=0 );
         pParse->apVarExpr[pParse->nVarExpr++] = pExpr;
       }
@@ -462,7 +462,8 @@ ExprList *sqlite3ExprListDup(ExprList *p){
       sqlite3TokenCopy(&pNewExpr->span, &pOldExpr->span);
     }
     assert( pNewExpr==0 || pNewExpr->span.z!=0 
-            || pOldExpr->span.z==0 || sqlite3ThreadData()->mallocFailed );
+            || pOldExpr->span.z==0
+            || sqlite3ThreadDataReadOnly()->mallocFailed );
     pItem->zName = sqliteStrDup(pOldItem->zName);
     pItem->sortOrder = pOldItem->sortOrder;
     pItem->isAgg = pOldItem->isAgg;
@@ -831,7 +832,7 @@ static int lookupName(
   zDb = sqlite3NameFromToken(pDbToken);
   zTab = sqlite3NameFromToken(pTableToken);
   zCol = sqlite3NameFromToken(pColumnToken);
-  if( sqlite3ThreadData()->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     goto lookupname_end;
   }
 
@@ -1308,7 +1309,7 @@ void sqlite3CodeSubselect(Parse *pParse, Expr *pExpr){
     int mem = pParse->nMem++;
     sqlite3VdbeAddOp(v, OP_MemLoad, mem, 0);
     testAddr = sqlite3VdbeAddOp(v, OP_If, 0, 0);
-    assert( testAddr>0 || sqlite3ThreadData()->mallocFailed );
+    assert( testAddr>0 || sqlite3ThreadDataReadOnly()->mallocFailed );
     sqlite3VdbeAddOp(v, OP_MemInt, 1, mem);
   }
 
diff --git a/src/insert.c b/src/insert.c
index 3d4c460b6..e24968690 100644
--- a/src/insert.c
+++ b/src/insert.c
@@ -12,7 +12,7 @@
 ** This file contains C code routines that are called by the parser
 ** to handle INSERT statements in SQLite.
 **
-** $Id: insert.c,v 1.156 2006/01/10 17:58:23 danielk1977 Exp $
+** $Id: insert.c,v 1.157 2006/01/11 21:41:22 drh Exp $
 */
 #include "sqliteInt.h"
 
@@ -225,7 +225,9 @@ void sqlite3Insert(
   int counterRowid;     /* Memory cell holding rowid of autoinc counter */
 #endif
 
-  if( pParse->nErr || sqlite3ThreadData()->mallocFailed ) goto insert_cleanup;
+  if( pParse->nErr || sqlite3ThreadDataReadOnly()->mallocFailed ){
+    goto insert_cleanup;
+  }
   db = pParse->db;
 
   /* Locate the table into which we will be inserting new information.
@@ -331,7 +333,9 @@ void sqlite3Insert(
 
     /* Resolve the expressions in the SELECT statement and execute it. */
     rc = sqlite3Select(pParse, pSelect, SRT_Subroutine, iInsertBlock,0,0,0,0);
-    if( rc || pParse->nErr || sqlite3ThreadData()->mallocFailed ) goto insert_cleanup;
+    if( rc || pParse->nErr || sqlite3ThreadDataReadOnly()->mallocFailed ){
+      goto insert_cleanup;
+    }
 
     iCleanup = sqlite3VdbeMakeLabel(v);
     sqlite3VdbeAddOp(v, OP_Goto, 0, iCleanup);
diff --git a/src/legacy.c b/src/legacy.c
index 2d928aeac..b149f5b29 100644
--- a/src/legacy.c
+++ b/src/legacy.c
@@ -14,7 +14,7 @@
 ** other files are for internal use by SQLite and should not be
 ** accessed by users of the library.
 **
-** $Id: legacy.c,v 1.10 2006/01/09 06:29:49 danielk1977 Exp $
+** $Id: legacy.c,v 1.11 2006/01/11 21:41:22 drh Exp $
 */
 
 #include "sqliteInt.h"
@@ -121,7 +121,7 @@ exec_out:
   if( pStmt ) sqlite3_finalize(pStmt);
   if( azCols ) sqliteFree(azCols);
 
-  if( sqlite3ThreadData()->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     rc = SQLITE_NOMEM;
     sqlite3MallocClearFailed();
   }
diff --git a/src/main.c b/src/main.c
index 1b4c04900..3ea1fc32c 100644
--- a/src/main.c
+++ b/src/main.c
@@ -14,7 +14,7 @@
 ** other files are for internal use by SQLite and should not be
 ** accessed by users of the library.
 **
-** $Id: main.c,v 1.322 2006/01/10 13:58:48 drh Exp $
+** $Id: main.c,v 1.323 2006/01/11 21:41:22 drh Exp $
 */
 #include "sqliteInt.h"
 #include "os.h"
@@ -176,9 +176,9 @@ int sqlite3_close(sqlite3 *db){
   ** structure?
   */
   sqliteFree(db->aDb[1].pSchema);
-
   sqliteFree(db);
   sqlite3MallocAllow();
+  sqlite3ReleaseThreadData();
   return SQLITE_OK;
 }
 
@@ -645,7 +645,7 @@ int sqlite3BtreeFactory(
 */
 const char *sqlite3_errmsg(sqlite3 *db){
   const char *z;
-  if( sqlite3ThreadData()->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     return sqlite3ErrStr(SQLITE_NOMEM);
   }
   if( sqlite3SafetyCheck(db) || db->errCode==SQLITE_MISUSE ){
@@ -684,7 +684,7 @@ const void *sqlite3_errmsg16(sqlite3 *db){
   };
 
   const void *z;
-  if( sqlite3ThreadData()->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     return (void *)(&outOfMemBe[SQLITE_UTF16NATIVE==SQLITE_UTF16LE?1:0]);
   }
   if( sqlite3SafetyCheck(db) || db->errCode==SQLITE_MISUSE ){
@@ -705,7 +705,7 @@ const void *sqlite3_errmsg16(sqlite3 *db){
 ** passed to this function, we assume a malloc() failed during sqlite3_open().
 */
 int sqlite3_errcode(sqlite3 *db){
-  if( !db || sqlite3ThreadData()->mallocFailed ){
+  if( !db || sqlite3ThreadDataReadOnly()->mallocFailed ){
     return SQLITE_NOMEM;
   }
   if( sqlite3SafetyCheck(db) ){
@@ -727,7 +727,7 @@ static int openDatabase(
   int rc;
   CollSeq *pColl;
 
-  assert( !sqlite3ThreadData()->mallocFailed );
+  assert( !sqlite3ThreadDataReadOnly()->mallocFailed );
 
   /* Allocate the sqlite data structure */
   db = sqliteMalloc( sizeof(sqlite3) );
@@ -854,7 +854,7 @@ int sqlite3_open16(
       rc = sqlite3_exec(*ppDb, "PRAGMA encoding = 'UTF-16'", 0, 0, 0);
     }
   }else{
-    assert( sqlite3ThreadData()->mallocFailed );
+    assert( sqlite3ThreadDataReadOnly()->mallocFailed );
     sqlite3MallocClearFailed();
   }
   sqlite3ValueFree(pVal);
@@ -1077,6 +1077,17 @@ int sqlite3_enable_shared_cache(int enable){
   }
 
   pTd->useSharedData = enable;
+  sqlite3ReleaseThreadData();
   return SQLITE_OK;
 }
 #endif
+
+/*
+** This is a convenience routine that makes sure that all thread-specific
+** data for this thread has been deallocated.
+*/
+void sqlite3_thread_cleanup(void){
+  ThreadData *pTd = sqlite3ThreadData();
+  memset(pTd, 0, sizeof(*pTd));
+  sqlite3ReleaseThreadData();
+}
diff --git a/src/os.h b/src/os.h
index 3123cba1b..5a33df408 100644
--- a/src/os.h
+++ b/src/os.h
@@ -292,7 +292,7 @@ int sqlite3OsCurrentTime(double*);
 void sqlite3OsEnterMutex(void);
 void sqlite3OsLeaveMutex(void);
 int sqlite3OsInMutex(void);
-void *sqlite3OsThreadSpecificData(int);
+ThreadData *sqlite3OsThreadSpecificData(int);
 void *sqlite3OsMalloc(int);
 void *sqlite3OsRealloc(void *, int);
 void sqlite3OsFree(void *);
@@ -335,7 +335,7 @@ struct sqlite3OsVtbl {
   void (*xEnterMutex)(void);
   void (*xLeaveMutex)(void);
   int (*xInMutex)(void);
-  void *(*xThreadSpecificData)(int);
+  ThreadData *(*xThreadSpecificData)(int);
 
   void *(*xMalloc)(int);
   void *(*xRealloc)(void *, int);
diff --git a/src/os_unix.c b/src/os_unix.c
index 42570c6ae..e603151a9 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -1627,38 +1627,27 @@ int sqlite3UnixInMutex(){
 }
 
 /*
-** This function is called automatically when a thread exists to delete
-** the threads ThreadData structure. 
+** If called with allocateFlag==1, then return a pointer to thread
+** specific data for the current thread.  Allocate and zero the
+** thread-specific data if it does not already exist necessary.
 **
-** Because the ThreadData structure is required by higher level routines
-** such as sqliteMalloc() we use OsFree() and OsMalloc() directly to
-** allocate the thread specific data.
+** If called with allocateFlag==0, then check the current thread
+** specific data.  If it exists and is all zeros, then deallocate it.
+** Return a pointer to the thread specific data or NULL if it is
+** unallocated.
 */
-#ifdef SQLITE_UNIX_THREADS
-static void deleteTsd(void *pTsd){
-  sqlite3OsFree(pTsd);
-}
-#endif
-
-/* 
-** The first time this function is called from a specific thread, nByte 
-** bytes of data area are allocated and zeroed. A pointer to the new 
-** allocation is returned to the caller. 
-**
-** Each subsequent call to this function from the thread returns the same
-** pointer. The argument is ignored in this case.
-*/
-void *sqlite3UnixThreadSpecificData(int nByte){
+ThreadData *sqlite3UnixThreadSpecificData(int allocateFlag){
+  static const ThreadData zeroData;
 #ifdef SQLITE_UNIX_THREADS
   static pthread_key_t key;
   static int keyInit = 0;
-  void *pTsd;
+  ThreadData *pTsd;
 
   if( !keyInit ){
     sqlite3OsEnterMutex();
     if( !keyInit ){
       int rc;
-      rc = pthread_key_create(&key, deleteTsd);
+      rc = pthread_key_create(&key, 0);
       if( rc ){
         sqlite3OsLeaveMutex();
         return 0;
@@ -1669,21 +1658,32 @@ void *sqlite3UnixThreadSpecificData(int nByte){
   }
 
   pTsd = pthread_getspecific(key);
-  if( !pTsd ){
-    pTsd = sqlite3OsMalloc(nByte);
-    if( pTsd ){
-      memset(pTsd, 0, nByte);
-      pthread_setspecific(key, pTsd);
+  if( allocateFlag ){
+    if( pTsd==0 ){
+      pTsd = sqlite3OsMalloc(sizeof(zeroData));
+      if( pTsd ){
+        *pTsd = zeroData;
+        pthread_setspecific(key, pTsd);
+      }
     }
+  }else if( pTsd!=0 && memcmp(pTsd, &zeroData, sizeof(zeroData))==0 ){
+    sqlite3OsFree(pTsd);
+    pthread_setspecific(key, 0);
+    pTsd = 0;
   }
   return pTsd;
 #else
-  static void *pTsd = 0;
-  if( !pTsd ){
-    pTsd = sqlite3OsMalloc(nByte);
-    if( pTsd ){
-      memset(pTsd, 0, nByte);
+  static ThreadData *pTsd = 0;
+  if( allocateFlag ){
+    if( pTsd==0 ){
+      pTsd = sqlite3OsMalloc( sizeof(zeroData) );
+      if( pTsd ){
+        *pTsd = zeroData;
+      }
     }
+  }else if( pTsd!=0 && memcmp(pTsd, &zeroData, sizeof(zeroData))==0 ){
+    sqlite3OsFree(pTsd);
+    pTsd = 0;
   }
   return pTsd;
 #endif
diff --git a/src/os_win.c b/src/os_win.c
index 38a1a3b7a..4675c4888 100644
--- a/src/os_win.c
+++ b/src/os_win.c
@@ -1148,18 +1148,21 @@ int sqlite3WinCurrentTime(double *prNow){
   return 0;
 }
 
-/* 
-** The first time this function is called from a specific thread, nByte 
-** bytes of data area are allocated and zeroed. A pointer to the new 
-** allocation is returned to the caller. 
+/*
+** If called with allocateFlag==1, then return a pointer to thread
+** specific data for the current thread.  Allocate and zero the
+** thread-specific data if it does not already exist necessary.
 **
-** Each subsequent call to this function from the thread returns the same
-** pointer. The argument is ignored in this case.
+** If called with allocateFlag==0, then check the current thread
+** specific data.  If it exists and is all zeros, then deallocate it.
+** Return a pointer to the thread specific data or NULL if it is
+** unallocated.
 */
-void *sqlite3WinThreadSpecificData(int nByte){
+void *sqlite3WinThreadSpecificData(int allocateFlag){
   static void *pTsd = 0;
   static int key;
   static int keyInit = 0;
+  static const ThreadData zeroData;
 
   if( !keyInit ){
     sqlite3OsEnterMutex();
@@ -1174,12 +1177,18 @@ void *sqlite3WinThreadSpecificData(int nByte){
     sqlite3OsLeaveMutex();
   }
   pTsd = TlsGetValue(key);
-  if( !pTsd ){
-    pTsd = sqlite3OsMalloc(nByte);
-    if( pTsd ){
-      memset(pTsd, 0, nByte);
-      TlsSetValue(key, pTsd);
+  if( allocateFlag ){
+    if( !pTsd ){
+      pTsd = sqlite3OsMalloc(nByte);
+      if( pTsd ){
+        *pTsd = zeroData;
+        TlsSetValue(key, pTsd);
+      }
     }
+  }else if( pTsd!=0 && memcmp(pTsd, &zeroData, sizeof(zeroData))==0 ){
+    sqlite3OsFree(pTsd);
+    TlsSetValue(key, 0);
+    pTsd = 0;
   }
   return pTsd;
 }
diff --git a/src/pager.c b/src/pager.c
index a8d601e52..7bf505494 100644
--- a/src/pager.c
+++ b/src/pager.c
@@ -18,7 +18,7 @@
 ** file simultaneously, or one process from reading the database while
 ** another is writing.
 **
-** @(#) $Id: pager.c,v 1.235 2006/01/10 20:32:32 drh Exp $
+** @(#) $Id: pager.c,v 1.236 2006/01/11 21:41:22 drh Exp $
 */
 #ifndef SQLITE_OMIT_DISKIO
 #include "sqliteInt.h"
@@ -284,7 +284,7 @@ struct Pager {
   void (*xCodec)(void*,void*,Pgno,int); /* Routine for en/decoding data */
   void *pCodecArg;            /* First argument to xCodec() */
   PgHdr *aHash[N_PG_HASH];    /* Hash table to map page number to PgHdr */
-#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
   Pager *pNext;               /* Linked list of pagers in this thread */
 #endif
 };
@@ -1618,8 +1618,8 @@ int sqlite3pager_open(
   int useJournal = (flags & PAGER_OMIT_JOURNAL)==0;
   int noReadlock = (flags & PAGER_NO_READLOCK)!=0;
   char zTemp[SQLITE_TEMPNAME_SIZE];
-#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
-  ThreadData *pTsd = sqlite3ThreadData();
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+  const ThreadData *pTsdro = sqlite3ThreadDataReadOnly();
 #endif
 
   /* If malloc() has already failed return SQLITE_NOMEM. Before even
@@ -1627,7 +1627,7 @@ int sqlite3pager_open(
   ** structure was never allocated. 
   */
   *ppPager = 0;
-  if( sqlite3ThreadData()->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     return SQLITE_NOMEM;
   }
   memset(&fd, 0, sizeof(fd));
@@ -1720,8 +1720,9 @@ int sqlite3pager_open(
   pPager->pBusyHandler = 0;
   memset(pPager->aHash, 0, sizeof(pPager->aHash));
   *ppPager = pPager;
-#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
-  if( pTsd->useMemoryManagement ){
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+  if( pTsdro->useMemoryManagement ){
+    ThreadData *pTsd = sqlite3ThreadData();
     pPager->pNext = pTsd->pPager;
     pTsd->pPager = pPager;
   }
@@ -2027,8 +2028,8 @@ int sqlite3pager_truncate(Pager *pPager, Pgno nPage){
 */
 int sqlite3pager_close(Pager *pPager){
   PgHdr *pPg, *pNext;
-#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
-  ThreadData *pTsd = sqlite3ThreadData();
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+  const ThreadData *pTsd = sqlite3ThreadDataReadOnly();
 #endif
 
   switch( pPager->state ){
@@ -2087,7 +2088,7 @@ int sqlite3pager_close(Pager *pPager){
   ** }
   */
 
-#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
   /* Remove the pager from the linked list of pagers starting at 
   ** ThreadData.pPager if memory-management is enabled.
   */
@@ -2456,9 +2457,9 @@ static int pager_recycle(Pager *pPager, int syncOk, PgHdr **ppPg){
 ** free as much memory as possible. The return value is the total number 
 ** of bytes of memory released.
 */
-#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
 int sqlite3pager_release_memory(int nReq){
-  ThreadData *pTsd = sqlite3ThreadData();
+  const ThreadData *pTsdro = sqlite3ThreadDataReadOnly();
   Pager *p;
   int nReleased = 0;
   int i;
@@ -2481,7 +2482,7 @@ int sqlite3pager_release_memory(int nReq){
   for(i=0; i<=1; i++){
 
     /* Loop through all the SQLite pagers opened by the current thread. */
-    for(p=pTsd->pPager; p && (nReq<0 || nReleased<nReq); p=p->pNext){
+    for(p=pTsdro->pPager; p && (nReq<0 || nReleased<nReq); p=p->pNext){
       PgHdr *pPg;
       int rc;
 
@@ -2527,7 +2528,7 @@ int sqlite3pager_release_memory(int nReq){
 
   return nReleased;
 }
-#endif /* SQLITE_OMIT_MEMORY_MANAGEMENT */
+#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */
 
 /*
 ** Acquire a page.
diff --git a/src/prepare.c b/src/prepare.c
index fcd0d19bd..d8d151094 100644
--- a/src/prepare.c
+++ b/src/prepare.c
@@ -13,7 +13,7 @@
 ** interface, and routines that contribute to loading the database schema
 ** from disk.
 **
-** $Id: prepare.c,v 1.19 2006/01/11 14:09:32 danielk1977 Exp $
+** $Id: prepare.c,v 1.20 2006/01/11 21:41:22 drh Exp $
 */
 #include "sqliteInt.h"
 #include "os.h"
@@ -24,7 +24,7 @@
 ** that the database is corrupt.
 */
 static void corruptSchema(InitData *pData, const char *zExtra){
-  if( !sqlite3ThreadData()->mallocFailed ){
+  if( !sqlite3ThreadDataReadOnly()->mallocFailed ){
     sqlite3SetString(pData->pzErrMsg, "malformed database schema",
        zExtra!=0 && zExtra[0]!=0 ? " - " : (char*)0, zExtra, (char*)0);
   }
@@ -49,7 +49,7 @@ int sqlite3InitCallback(void *pInit, int argc, char **argv, char **azColName){
   sqlite3 *db = pData->db;
   int iDb;
 
-  if( sqlite3ThreadData()->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     return SQLITE_NOMEM;
   }
 
@@ -303,7 +303,7 @@ static int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg){
 #endif
     sqlite3BtreeCloseCursor(curMain);
   }
-  if( sqlite3ThreadData()->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     sqlite3SetString(pzErrMsg, "out of memory", (char*)0);
     rc = SQLITE_NOMEM;
     sqlite3ResetInternalSchema(db, 0);
@@ -494,7 +494,7 @@ int sqlite3_prepare(
   int rc = SQLITE_OK;
   int i;
 
-  assert( !sqlite3ThreadData()->mallocFailed );
+  assert( !sqlite3ThreadDataReadOnly()->mallocFailed );
 
   assert( ppStmt );
   *ppStmt = 0;
@@ -519,7 +519,7 @@ int sqlite3_prepare(
   sParse.db = db;
   sqlite3RunParser(&sParse, zSql, &zErrMsg);
 
-  if( sqlite3ThreadData()->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     sParse.rc = SQLITE_NOMEM;
   }
   if( sParse.rc==SQLITE_DONE ) sParse.rc = SQLITE_OK;
@@ -569,7 +569,7 @@ int sqlite3_prepare(
   /* We must check for malloc failure last of all, in case malloc() failed
   ** inside of the sqlite3Error() call above or something.
   */
-  if( sqlite3ThreadData()->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     rc = SQLITE_NOMEM;
     sqlite3Error(db, rc, 0);
   }
diff --git a/src/select.c b/src/select.c
index 145f319b0..d0fff323c 100644
--- a/src/select.c
+++ b/src/select.c
@@ -12,7 +12,7 @@
 ** This file contains C code routines that are called by the parser
 ** to handle SELECT statements in SQLite.
 **
-** $Id: select.c,v 1.292 2006/01/10 17:58:23 danielk1977 Exp $
+** $Id: select.c,v 1.293 2006/01/11 21:41:22 drh Exp $
 */
 #include "sqliteInt.h"
 
@@ -872,7 +872,8 @@ static void generateColumnNames(
 #endif
 
   assert( v!=0 );
-  if( pParse->colNamesSet || v==0 || sqlite3ThreadData()->mallocFailed ) return;
+  if( pParse->colNamesSet || v==0
+     || sqlite3ThreadDataReadOnly()->mallocFailed ) return;
   pParse->colNamesSet = 1;
   fullNames = (db->flags & SQLITE_FullColNames)!=0;
   shortNames = (db->flags & SQLITE_ShortColNames)!=0;
@@ -1001,7 +1002,7 @@ Table *sqlite3ResultSetOfSelect(Parse *pParse, char *zTabName, Select *pSelect){
       zName = sqlite3MPrintf("column%d", i+1);
     }
     sqlite3Dequote(zName);
-    if( sqlite3ThreadData()->mallocFailed ){
+    if( sqlite3ThreadDataReadOnly()->mallocFailed ){
       sqliteFree(zName);
       sqlite3DeleteTable(0, pTab);
       return 0;
@@ -1073,7 +1074,9 @@ static int prepSelectStmt(Parse *pParse, Select *p){
   Table *pTab;
   struct SrcList_item *pFrom;
 
-  if( p==0 || p->pSrc==0 || sqlite3ThreadData()->mallocFailed ) return 1;
+  if( p==0 || p->pSrc==0 || sqlite3ThreadDataReadOnly()->mallocFailed ){
+    return 1;
+  }
   pTabList = p->pSrc;
   pEList = p->pEList;
 
@@ -2690,7 +2693,9 @@ int sqlite3Select(
   AggInfo sAggInfo;      /* Information used by aggregate queries */
   int iEnd;              /* Address of the end of the query */
 
-  if( sqlite3ThreadData()->mallocFailed || pParse->nErr || p==0 ) return 1;
+  if( p==0 || sqlite3ThreadDataReadOnly()->mallocFailed || pParse->nErr ){
+    return 1;
+  }
   if( sqlite3AuthCheck(pParse, SQLITE_SELECT, 0, 0, 0) ) return 1;
   memset(&sAggInfo, 0, sizeof(sAggInfo));
 
@@ -2944,7 +2949,7 @@ int sqlite3Select(
         goto select_end;
       }
     }
-    if( sqlite3ThreadData()->mallocFailed ) goto select_end;
+    if( sqlite3ThreadDataReadOnly()->mallocFailed ) goto select_end;
 
     /* Processing for aggregates with GROUP BY is very different and
     ** much more complex tha aggregates without a GROUP BY.
diff --git a/src/sqlite.h.in b/src/sqlite.h.in
index c43b7cd0d..92caceedd 100644
--- a/src/sqlite.h.in
+++ b/src/sqlite.h.in
@@ -12,7 +12,7 @@
 ** This header file defines the interface that the SQLite library
 ** presents to client programs.
 **
-** @(#) $Id: sqlite.h.in,v 1.154 2006/01/10 15:18:28 drh Exp $
+** @(#) $Id: sqlite.h.in,v 1.155 2006/01/11 21:41:22 drh Exp $
 */
 #ifndef _SQLITE3_H_
 #define _SQLITE3_H_
@@ -1330,20 +1330,12 @@ void *sqlite3_rollback_hook(sqlite3*, void(*)(void *), void*);
 int sqlite3_enable_shared_cache(int);
 
 /*
-** This function is only available if the library is compiled without
-** the SQLITE_OMIT_MEMORY_MANAGEMENT macro defined. It is used to enable or
-** disable (if the argument is true or false, respectively) the 
-** "memory management" features (accessed via the sqlite3_soft_heap_limit()
-** and sqlite3_release_memory() APIs).
-*/
-int sqlite3_enable_memory_management(int);
-
-/*
 ** Attempt to free N bytes of heap memory by deallocating non-essential
 ** memory allocations held by the database library (example: memory 
 ** used to cache database pages to improve performance).
 **
-** This function is a no-op unless memory-management has been enabled.
+** This function is not a part of standard builds.  It is only created
+** if SQLite is compiled with the SQLITE_ENABLE_MEMORY_MANAGEMENT macro.
 */
 int sqlite3_release_memory(int);
 
@@ -1357,13 +1349,26 @@ int sqlite3_release_memory(int);
 ** sufficient memory to prevent the limit from being exceeded, the memory is
 ** allocated anyway and the current operation proceeds.
 **
-** This function is only available if the library was compiled without the 
-** SQLITE_OMIT_MEMORY_MANAGEMENT option set. It is a no-op unless 
+** This function is only available if the library was compiled with the 
+** SQLITE_ENABLE_MEMORY_MANAGEMENT option set.
 ** memory-management has been enabled.
 */
 void sqlite3_soft_heap_limit(int);
 
 /*
+** This routine makes sure that all thread-local storage has been
+** deallocated for the current thread.
+**
+** This routine is not technically necessary.  All thread-local storage
+** will be automatically deallocated once memory-management and
+** shared-cache are disabled and the soft heap limit has been set
+** to zero.  This routine is provided as a convenience for users who
+** want to make absolutely sure they have not forgotten something
+** prior to killing off a thread.
+*/
+void sqlite3_thread_cleanup(void);
+
+/*
 ** Undo the hack that converts floating point types to integer for
 ** builds on processors without floating point support.
 */
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 1710f9293..9f5591faf 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -11,7 +11,7 @@
 *************************************************************************
 ** Internal interface definitions for SQLite.
 **
-** @(#) $Id: sqliteInt.h,v 1.461 2006/01/11 14:09:32 danielk1977 Exp $
+** @(#) $Id: sqliteInt.h,v 1.462 2006/01/11 21:41:22 drh Exp $
 */
 #ifndef _SQLITEINT_H_
 #define _SQLITEINT_H_
@@ -286,14 +286,17 @@ extern int sqlite3_iMallocReset; /* Set iMallocFail to this when it reaches 0 */
 #define sqliteAllocSize(x)     sqlite3AllocSize(x)
 
 /*
-** An instance of this structure is allocated for each thread that uses SQLite.
+** An instance of this structure might be allocated to store information
+** specific to a single thread.
+**
+** To avoid a memory leak on windows, the content of this structure is
+** checked at the conclusion of each API call.  If it is all zero, it
+** is deallocated.
 */
 struct ThreadData {
-  u8 isInit;               /* True if structure has been initialised */
   u8 mallocFailed;         /* True after a malloc() has failed */
 
-#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
-  u8 useMemoryManagement;  /* True if memory-management is enabled */
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
   int nSoftHeapLimit;      /* Suggested max mem allocation.  No limit if <0 */
   int nAlloc;              /* Number of bytes currently allocated */
   Pager *pPager;           /* Linked list of all pagers in this thread */
@@ -306,7 +309,7 @@ struct ThreadData {
 
 #ifdef SQLITE_MEMDEBUG
   int nMaxAlloc;           /* High water mark of ThreadData.nAlloc */
-  int mallocAllowed;       /* assert() in sqlite3Malloc() if not set */
+  int mallocDisallowed;    /* assert() in sqlite3Malloc() if set */
   int isFail;              /* True if all malloc() calls should fail */
   const char *zFile;       /* Filename to associate debugging info with */
   int iLine;               /* Line number to associate debugging info with */
@@ -1730,7 +1733,9 @@ void sqlite3AnalysisLoad(sqlite3*,int iDB);
 void sqlite3DefaultRowEst(Index*);
 void sqlite3RegisterLikeFunctions(sqlite3*, int);
 int sqlite3IsLikeFunction(sqlite3*,Expr*,int*,char*);
-ThreadData *sqlite3ThreadData();
+ThreadData *sqlite3ThreadData(void);
+const ThreadData *sqlite3ThreadDataReadOnly(void);
+void sqlite3ReleaseThreadData(void);
 void sqlite3AttachFunctions(sqlite3 *);
 void sqlite3MinimumFileFormat(Parse*, int, int);
 void sqlite3SchemaFree(void *);
diff --git a/src/test1.c b/src/test1.c
index d98640b4c..891b5b4e2 100644
--- a/src/test1.c
+++ b/src/test1.c
@@ -13,7 +13,7 @@
 ** is not included in the SQLite library.  It is used for automated
 ** testing of the SQLite library.
 **
-** $Id: test1.c,v 1.187 2006/01/11 14:09:32 danielk1977 Exp $
+** $Id: test1.c,v 1.188 2006/01/11 21:41:22 drh Exp $
 */
 #include "sqliteInt.h"
 #include "tcl.h"
@@ -903,9 +903,9 @@ static int sqlite_malloc_outstanding(
 ){
   extern int sqlite3OutstandingMallocs(Tcl_Interp *interp);
 
-#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
   if( objc==2 ){
-    ThreadData *pTd = sqlite3ThreadData();
+    const ThreadData *pTd = sqlite3ThreadDataReadOnly();
     const char *zArg = Tcl_GetString(objv[1]);
     if( 0==strcmp(zArg, "-bytes") ){
       Tcl_SetObjResult(interp, Tcl_NewIntObj(pTd->nAlloc));
@@ -935,11 +935,10 @@ static int sqlite_malloc_outstanding(
 
 /*
 ** Usage: sqlite3_enable_shared_cache      BOOLEAN
-** Usage: sqlite3_enable_memory_management BOOLEAN
 **
 */
-#if !defined(SQLITE_OMIT_SHARED_CACHE)||!defined(SQLITE_OMIT_MEMORY_MANAGEMENT)
-static int test_enable(
+#if !defined(SQLITE_OMIT_SHARED_CACHE)
+static int test_enable_shared(
   ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
   Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
   int objc,              /* Number of arguments */
@@ -948,20 +947,7 @@ static int test_enable(
   int rc;
   int enable;
   int ret = 0;
-  int (*xFunc)(int) = (int(*)(int))clientData;
-  ThreadData *pTsd = sqlite3ThreadData();
 
-#ifndef SQLITE_OMIT_SHARED_CACHE
-  if( xFunc==sqlite3_enable_shared_cache ){
-    ret = pTsd->useSharedData;
-  }else
-#endif
-#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
-  {
-    assert( xFunc==sqlite3_enable_memory_management );
-    ret = pTsd->useMemoryManagement;
-  }
-#endif
   if( objc!=2 ){
     Tcl_WrongNumArgs(interp, 1, objv, "BOOLEAN");
     return TCL_ERROR;
@@ -969,7 +955,8 @@ static int test_enable(
   if( Tcl_GetBooleanFromObj(interp, objv[1], &enable) ){
     return TCL_ERROR;
   }
-  rc = xFunc(enable);
+  ret = sqlite3ThreadDataReadOnly()->useSharedData;
+  rc = sqlite3_enable_shared_cache(enable);
   if( rc!=SQLITE_OK ){
     Tcl_SetResult(interp, (char *)sqlite3ErrStr(rc), TCL_STATIC);
     return TCL_ERROR;
@@ -2966,7 +2953,7 @@ static int test_release_memory(
   int objc,
   Tcl_Obj *CONST objv[]
 ){
-#if !defined(SQLITE_OMIT_MEMORY_MANAGEMENT) && !defined(SQLITE_OMIT_DISKIO)
+#if defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) && !defined(SQLITE_OMIT_DISKIO)
   int N;
   int amt;
   if( objc!=1 && objc!=2 ){
@@ -2997,13 +2984,13 @@ static int test_soft_heap_limit(
   int objc,
   Tcl_Obj *CONST objv[]
 ){
-#if !defined(SQLITE_OMIT_MEMORY_MANAGEMENT) && !defined(SQLITE_OMIT_DISKIO)
+#if defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) && !defined(SQLITE_OMIT_DISKIO)
   int amt;
   if( objc!=1 && objc!=2 ){
     Tcl_WrongNumArgs(interp, 1, objv, "?N?");
     return TCL_ERROR;
   }
-  amt = sqlite3ThreadData()->nSoftHeapLimit;
+  amt = sqlite3ThreadDataReadOnly()->nSoftHeapLimit;
   if( objc==2 ){
     int N;
     if( Tcl_GetIntFromObj(interp, objv[1], &N) ) return TCL_ERROR;
@@ -3181,10 +3168,10 @@ static void set_options(Tcl_Interp *interp){
   Tcl_SetVar2(interp, "sqlite_options", "memorydb", "1", TCL_GLOBAL_ONLY);
 #endif
 
-#ifdef SQLITE_OMIT_MEMORY_MANAGEMENT
-  Tcl_SetVar2(interp, "sqlite_options", "memorymanage", "0", TCL_GLOBAL_ONLY);
-#else
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
   Tcl_SetVar2(interp, "sqlite_options", "memorymanage", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "memorymanage", "0", TCL_GLOBAL_ONLY);
 #endif
 
 #ifdef SQLITE_OMIT_OR_OPTIMIZATION
@@ -3429,11 +3416,7 @@ int Sqlitetest1_Init(Tcl_Interp *interp){
      { "sqlite3_test_errstr",     test_errstr, 0             },
      { "tcl_variable_type",       tcl_variable_type, 0       },
 #ifndef SQLITE_OMIT_SHARED_CACHE
-     { "sqlite3_enable_shared_cache", test_enable, sqlite3_enable_shared_cache},
-#endif
-#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
-     { "sqlite3_enable_memory_management", test_enable, 
-       sqlite3_enable_memory_management},
+     { "sqlite3_enable_shared_cache", test_enable_shared, 0  },
 #endif
   };
   static int bitmask_size = sizeof(Bitmask)*8;
diff --git a/src/tokenize.c b/src/tokenize.c
index 5645317ba..ec2efbe78 100644
--- a/src/tokenize.c
+++ b/src/tokenize.c
@@ -15,7 +15,7 @@
 ** individual tokens and sends those tokens one-by-one over to the
 ** parser for analysis.
 **
-** $Id: tokenize.c,v 1.112 2006/01/09 06:29:49 danielk1977 Exp $
+** $Id: tokenize.c,v 1.113 2006/01/11 21:41:22 drh Exp $
 */
 #include "sqliteInt.h"
 #include "os.h"
@@ -358,7 +358,7 @@ int sqlite3RunParser(Parse *pParse, const char *zSql, char **pzErrMsg){
   assert( pParse->nVarExprAlloc==0 );
   assert( pParse->apVarExpr==0 );
   pParse->zTail = pParse->zSql = zSql;
-  while( sqlite3ThreadData()->mallocFailed==0 && zSql[i]!=0 ){
+  while( sqlite3ThreadDataReadOnly()->mallocFailed==0 && zSql[i]!=0 ){
     assert( i>=0 );
     pParse->sLastToken.z = (u8*)&zSql[i];
     assert( pParse->sLastToken.dyn==0 );
@@ -406,7 +406,7 @@ abort_parse:
     sqlite3Parser(pEngine, 0, pParse->sLastToken, pParse);
   }
   sqlite3ParserFree(pEngine, sqlite3FreeX);
-  if( sqlite3ThreadData()->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     pParse->rc = SQLITE_NOMEM;
   }
   if( pParse->rc!=SQLITE_OK && pParse->rc!=SQLITE_DONE && pParse->zErrMsg==0 ){
diff --git a/src/trigger.c b/src/trigger.c
index fbe8951bb..6a031c0bd 100644
--- a/src/trigger.c
+++ b/src/trigger.c
@@ -81,14 +81,16 @@ void sqlite3BeginTrigger(
   ** If sqlite3SrcListLookup() returns 0, indicating the table does not
   ** exist, the error is caught by the block below.
   */
-  if( !pTableName || sqlite3ThreadData()->mallocFailed ) goto trigger_cleanup;
+  if( !pTableName || sqlite3ThreadDataReadOnly()->mallocFailed ){
+    goto trigger_cleanup;
+  }
   pTab = sqlite3SrcListLookup(pParse, pTableName);
   if( pName2->n==0 && pTab && pTab->pSchema==db->aDb[1].pSchema ){
     iDb = 1;
   }
 
   /* Ensure the table name matches database name and that the table exists */
-  if( sqlite3ThreadData()->mallocFailed ) goto trigger_cleanup;
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ) goto trigger_cleanup;
   assert( pTableName->nSrc==1 );
   if( sqlite3FixInit(&sFix, pParse, iDb, "trigger", pName) && 
       sqlite3FixSrcList(&sFix, pTableName) ){
@@ -255,7 +257,7 @@ void sqlite3FinishTrigger(
     pDel = sqlite3HashInsert(&db->aDb[iDb].pSchema->trigHash, 
                      pTrig->name, strlen(pTrig->name)+1, pTrig);
     if( pDel ){
-      assert( sqlite3ThreadData()->mallocFailed && pDel==pTrig );
+      assert( sqlite3ThreadDataReadOnly()->mallocFailed && pDel==pTrig );
       goto triggerfinish_cleanup;
     }
     n = strlen(pTrig->table) + 1;
@@ -439,7 +441,7 @@ void sqlite3DropTrigger(Parse *pParse, SrcList *pName){
   int nName;
   sqlite3 *db = pParse->db;
 
-  if( sqlite3ThreadData()->mallocFailed ) goto drop_trigger_cleanup;
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ) goto drop_trigger_cleanup;
   if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
     goto drop_trigger_cleanup;
   }
diff --git a/src/update.c b/src/update.c
index c44e24e1e..944ac039b 100644
--- a/src/update.c
+++ b/src/update.c
@@ -12,7 +12,7 @@
 ** This file contains C code routines that are called by the parser
 ** to handle UPDATE statements.
 **
-** $Id: update.c,v 1.119 2006/01/10 17:58:23 danielk1977 Exp $
+** $Id: update.c,v 1.120 2006/01/11 21:41:22 drh Exp $
 */
 #include "sqliteInt.h"
 
@@ -100,7 +100,9 @@ void sqlite3Update(
   int oldIdx      = -1;  /* index of trigger "old" temp table       */
 
   sContext.pParse = 0;
-  if( pParse->nErr || sqlite3ThreadData()->mallocFailed ) goto update_cleanup;
+  if( pParse->nErr || sqlite3ThreadDataReadOnly()->mallocFailed ){
+    goto update_cleanup;
+  }
   db = pParse->db;
   assert( pTabList->nSrc==1 );
 
diff --git a/src/util.c b/src/util.c
index 4064dadc9..846e9db16 100644
--- a/src/util.c
+++ b/src/util.c
@@ -14,7 +14,7 @@
 ** This file contains functions for allocating memory, comparing
 ** strings, and stuff like that.
 **
-** $Id: util.c,v 1.167 2006/01/11 16:10:20 danielk1977 Exp $
+** $Id: util.c,v 1.168 2006/01/11 21:41:22 drh Exp $
 */
 #include "sqliteInt.h"
 #include "os.h"
@@ -66,13 +66,14 @@
 
 #define MAX(x,y) ((x)>(y)?(x):(y))
 
-#if !defined(SQLITE_OMIT_MEMORY_MANAGEMENT) && !defined(SQLITE_OMIT_DISKIO)
+#if defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) && !defined(SQLITE_OMIT_DISKIO)
 /*
 ** Set the soft heap-size limit for the current thread. Passing a negative
 ** value indicates no limit.
 */
 void sqlite3_soft_heap_limit(int n){
   sqlite3ThreadData()->nSoftHeapLimit = n;
+  sqlite3ReleaseThreadData();
 }
 
 /*
@@ -82,7 +83,7 @@ int sqlite3_release_memory(int n){
   return sqlite3pager_release_memory(n);
 }
 #else
-/* If SQLITE_OMIT_MEMORY_MANAGEMENT is defined, then define a version
+/* If SQLITE_ENABLE_MEMORY_MANAGEMENT is not defined, then define a version
 ** of sqlite3_release_memory() to be used by other code in this file.
 ** This is done for no better reason than to reduce the number of 
 ** pre-processor #ifndef statements.
@@ -121,7 +122,9 @@ int sqlite3_release_memory(int n){
 ** 2 since on 64-bit machines we want the value returned by sqliteMalloc()
 ** to be 8-byte aligned.
 */
-#define TESTALLOC_NGUARD 2
+#ifndef TESTALLOC_NGUARD
+# define TESTALLOC_NGUARD 2
+#endif
 
 /*
 ** Size reserved for storing file-name along with each malloc()ed blob.
@@ -434,11 +437,11 @@ int sqlite3OutstandingMallocs(Tcl_Interp *interp){
 ** This is the test layer's wrapper around sqlite3OsMalloc().
 */
 static void * OSMALLOC(int n){
-#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
   ThreadData *pTsd = sqlite3ThreadData();
   pTsd->nMaxAlloc = MAX(pTsd->nMaxAlloc, pTsd->nAlloc);
 #endif
-  assert( sqlite3ThreadData()->mallocAllowed );
+  assert( !sqlite3ThreadData()->mallocDisallowed );
   if( !failMalloc() ){
     u32 *p;
     p = (u32 *)sqlite3OsMalloc(n + TESTALLOC_OVERHEAD);
@@ -476,11 +479,11 @@ static void OSFREE(void *pFree){
 ** This is the test layer's wrapper around sqlite3OsRealloc().
 */
 static void * OSREALLOC(void *pRealloc, int n){
-#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
   ThreadData *pTsd = sqlite3ThreadData();
   pTsd->nMaxAlloc = MAX(pTsd->nMaxAlloc, pTsd->nAlloc);
 #endif
-  assert( sqlite3ThreadData()->mallocAllowed );
+  assert( !sqlite3ThreadData()->mallocDisallowed );
   if( !failMalloc() ){
     u32 *p = (u32 *)getOsPointer(pRealloc);
     checkGuards(p);
@@ -521,14 +524,18 @@ static void OSMALLOC_FAILED(){
 ** called to try to avoid this. No indication of whether or not this is
 ** successful is returned to the caller.
 **
-** If SQLITE_OMIT_MEMORY_MANAGEMENT is defined, this function is a no-op.
+** If SQLITE_ENABLE_MEMORY_MANAGEMENT is not defined, this routine is
+** a no-op
 */
-#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
 static void handleSoftLimit(int n){
   ThreadData *pTsd = sqlite3ThreadData();
   pTsd->nAlloc += n;
+  assert( pTsd->nAlloc>=0 );
   if( n>0 && pTsd->nSoftHeapLimit>0 ){
     while( pTsd->nAlloc>pTsd->nSoftHeapLimit && sqlite3_release_memory(n) );
+  }else if( pTsd->nAlloc==0 && pTsd->nSoftHeapLimit==0 ){
+    sqlite3ReleaseThreadData();
   }
 }
 #else
@@ -541,9 +548,8 @@ static void handleSoftLimit(int n){
 ** by calling sqlite3_release_memory().
 */
 void *sqlite3MallocRaw(int n){
-  ThreadData *pTsd = sqlite3ThreadData();
   void *p = 0;
-  if( n>0 && !pTsd->mallocFailed ){
+  if( n>0 && !sqlite3ThreadDataReadOnly()->mallocFailed ){
     handleSoftLimit(n);
     while( !(p = OSMALLOC(n)) && sqlite3_release_memory(n) );
     if( !p ){
@@ -566,8 +572,7 @@ void *sqlite3MallocRaw(int n){
 ** attempt to free memory by calling sqlite3_release_memory().
 */
 void *sqlite3Realloc(void *p, int n){
-  ThreadData *pTsd = sqlite3ThreadData();
-  if( pTsd->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     return 0;
   }
 
@@ -584,7 +589,7 @@ void *sqlite3Realloc(void *p, int n){
       ** still correct after a malloc() failure. 
       */
       handleSoftLimit(OSSIZEOF(p) - n);
-      pTsd->mallocFailed = 1;
+      sqlite3ThreadData()->mallocFailed = 1;
       OSMALLOC_FAILED();
     }
     return np;
@@ -1308,46 +1313,39 @@ void *sqlite3TextToPtr(const char *z){
 ** Return a pointer to the ThreadData associated with the calling thread.
 */
 ThreadData *sqlite3ThreadData(){
-  ThreadData *pTsd = sqlite3OsThreadSpecificData(sizeof(ThreadData));
-  if( pTsd && !pTsd->isInit ){
-#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
-    pTsd->nSoftHeapLimit = -1;
-#endif
-#ifndef NDEBUG
-    pTsd->mallocAllowed = 1;
-#endif
-    pTsd->isInit = 1;
-  }
-  return pTsd;
+  return (ThreadData*)sqlite3OsThreadSpecificData(1);
 }
 
 /*
-** Clear the "mallocFailed" flag. This should be invoked before exiting any
-** entry points that may have called sqliteMalloc().
+** Return a pointer to the ThreadData associated with the calling thread.
+** If no ThreadData has been allocated to this thread yet, return a pointer
+** to a substitute ThreadData structure that is all zeros. 
 */
-void sqlite3MallocClearFailed(){
-  sqlite3ThreadData()->mallocFailed = 0;
+const ThreadData *sqlite3ThreadDataReadOnly(){
+  static const ThreadData zeroData;
+  const ThreadData *pTd = sqlite3OsThreadSpecificData(0);
+  return pTd ? pTd : &zeroData;
 }
 
-#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
 /*
-** Enable the shared pager and schema features.
+** Check to see if the ThreadData for this thread is all zero.  If it
+** is, then deallocate it. 
 */
-int sqlite3_enable_memory_management(int enable){
-  ThreadData *pTsd = sqlite3ThreadData();
+void sqlite3ReleaseThreadData(){
+  sqlite3OsThreadSpecificData(0);
+}
 
-  /* It is only legal to call sqlite3_enable_memory_management() when there
-  ** are no currently open connections that were opened by the calling 
-  ** thread. This condition is only easy to detect if the feature were
-  ** previously enabled (and is being disabled). 
-  */
-  if( pTsd->pPager && !enable ){
-    return SQLITE_MISUSE;
+/*
+** Clear the "mallocFailed" flag. This should be invoked before exiting any
+** entry points that may have called sqliteMalloc().
+*/
+void sqlite3MallocClearFailed(){
+  ThreadData *pTd = sqlite3OsThreadSpecificData(0);
+  if( pTd && pTd->mallocFailed ){
+    pTd->mallocFailed = 0;
+    sqlite3OsThreadSpecificData(0);
   }
-  pTsd->useMemoryManagement = enable;
-  return SQLITE_OK;
 }
-#endif
 
 #ifndef NDEBUG
 /*
@@ -1355,8 +1353,8 @@ int sqlite3_enable_memory_management(int enable){
 ** cause an assert to fail if sqliteMalloc() or sqliteRealloc() is called.
 */
 void sqlite3MallocDisallow(){
-  assert(sqlite3ThreadData()->mallocAllowed);
-  sqlite3ThreadData()->mallocAllowed = 0;
+  assert(!sqlite3ThreadData()->mallocDisallowed);
+  sqlite3ThreadData()->mallocDisallowed = 1;
 }
 
 /*
@@ -1364,7 +1362,7 @@ void sqlite3MallocDisallow(){
 ** by sqlite3MallocDisallow().
 */
 void sqlite3MallocAllow(){
-  assert(!sqlite3ThreadData()->mallocAllowed);
-  sqlite3ThreadData()->mallocAllowed = 1;
+  assert(sqlite3ThreadData()->mallocDisallowed);
+  sqlite3ThreadData()->mallocDisallowed = 0;
 }
 #endif
diff --git a/src/vdbe.c b/src/vdbe.c
index 8fefed830..04bf97d53 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -43,7 +43,7 @@
 ** in this file for details.  If in doubt, do not deviate from existing
 ** commenting and indentation practices when changing or adding code.
 **
-** $Id: vdbe.c,v 1.522 2006/01/10 19:45:49 drh Exp $
+** $Id: vdbe.c,v 1.523 2006/01/11 21:41:22 drh Exp $
 */
 #include "sqliteInt.h"
 #include "os.h"
@@ -412,7 +412,7 @@ int sqlite3VdbeExec(
   for(pc=p->pc; rc==SQLITE_OK; pc++){
     assert( pc>=0 && pc<p->nOp );
     assert( pTos<=&p->aStack[pc] );
-    if( sqlite3ThreadData()->mallocFailed ) goto no_mem;
+    if( sqlite3ThreadDataReadOnly()->mallocFailed ) goto no_mem;
 #ifdef VDBE_PROFILE
     origPc = pc;
     start = hwtime();
@@ -1167,7 +1167,7 @@ case OP_Function: {
   if( sqlite3SafetyOff(db) ) goto abort_due_to_misuse;
   (*ctx.pFunc->xFunc)(&ctx, n, apVal);
   if( sqlite3SafetyOn(db) ) goto abort_due_to_misuse;
-  if( sqlite3ThreadData()->mallocFailed ) goto no_mem;
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ) goto no_mem;
   popStack(&pTos, n);
 
   /* If any auxilary data functions have been called by this user function,
@@ -4020,7 +4020,7 @@ case OP_ParseSchema: {        /* no-push */
   sqlite3SafetyOff(db);
   assert( db->init.busy==0 );
   db->init.busy = 1;
-  assert(0==sqlite3ThreadData()->mallocFailed);
+  assert(0==sqlite3ThreadDataReadOnly()->mallocFailed);
   rc = sqlite3_exec(db, zSql, sqlite3InitCallback, &initData, 0);
   sqliteFree(zSql);
   db->init.busy = 0;
@@ -4616,7 +4616,7 @@ abort_due_to_misuse:
   */
 abort_due_to_error:
   if( p->zErrMsg==0 ){
-    if( sqlite3ThreadData()->mallocFailed ) rc = SQLITE_NOMEM;
+    if( sqlite3ThreadDataReadOnly()->mallocFailed ) rc = SQLITE_NOMEM;
     sqlite3SetString(&p->zErrMsg, sqlite3ErrStr(rc), (char*)0);
   }
   goto vdbe_halt;
diff --git a/src/vdbeapi.c b/src/vdbeapi.c
index 462f38023..74bd8bd9d 100644
--- a/src/vdbeapi.c
+++ b/src/vdbeapi.c
@@ -156,7 +156,7 @@ int sqlite3_step(sqlite3_stmt *pStmt){
   sqlite3 *db;
   int rc;
 
-  assert(!sqlite3ThreadData()->mallocFailed);
+  assert(!sqlite3ThreadDataReadOnly()->mallocFailed);
 
   if( p==0 || p->magic!=VDBE_MAGIC_RUN ){
     return SQLITE_MISUSE;
@@ -404,7 +404,7 @@ static void columnMallocFailure(sqlite3_stmt *pStmt)
   ** SQLITE_NOMEM. The next call to _step() (if any) will return SQLITE_ERROR
   ** and _finalize() will return NOMEM.
   */
-  if( sqlite3ThreadData()->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     ((Vdbe *)pStmt)->rc = SQLITE_NOMEM;
     sqlite3MallocClearFailed();
   }
diff --git a/src/vdbeaux.c b/src/vdbeaux.c
index 3080af59e..ab8282eae 100644
--- a/src/vdbeaux.c
+++ b/src/vdbeaux.c
@@ -102,7 +102,7 @@ int sqlite3VdbeAddOp(Vdbe *p, int op, int p1, int p2){
   p->nOp++;
   assert( p->magic==VDBE_MAGIC_INIT );
   resizeOpArray(p, i+1);
-  if( sqlite3ThreadData()->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     return 0;
   }
   pOp = &p->aOp[i];
@@ -301,7 +301,7 @@ int sqlite3VdbeAddOpList(Vdbe *p, int nOp, VdbeOpList const *aOp){
   int addr;
   assert( p->magic==VDBE_MAGIC_INIT );
   resizeOpArray(p, p->nOp + nOp);
-  if( sqlite3ThreadData()->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     return 0;
   }
   addr = p->nOp;
@@ -415,7 +415,7 @@ static void freeP3(int p3type, void *p3){
 void sqlite3VdbeChangeP3(Vdbe *p, int addr, const char *zP3, int n){
   Op *pOp;
   assert( p->magic==VDBE_MAGIC_INIT );
-  if( p==0 || p->aOp==0 || sqlite3ThreadData()->mallocFailed ){
+  if( p==0 || p->aOp==0 || sqlite3ThreadDataReadOnly()->mallocFailed ){
     if (n != P3_KEYINFO) {
       freeP3(n, (void*)*(char**)&zP3);
     }
@@ -472,7 +472,8 @@ void sqlite3VdbeChangeP3(Vdbe *p, int addr, const char *zP3, int n){
 void sqlite3VdbeComment(Vdbe *p, const char *zFormat, ...){
   va_list ap;
   assert( p->nOp>0 );
-  assert( p->aOp==0 || p->aOp[p->nOp-1].p3==0 || sqlite3ThreadData()->mallocFailed );
+  assert( p->aOp==0 || p->aOp[p->nOp-1].p3==0 
+          || sqlite3ThreadDataReadOnly()->mallocFailed );
   va_start(ap, zFormat);
   sqlite3VdbeChangeP3(p, -1, sqlite3VMPrintf(zFormat, ap), P3_DYNAMIC);
   va_end(ap);
@@ -738,7 +739,7 @@ void sqlite3VdbeMakeReady(
       + nMem*sizeof(Mem)               /* aMem */
       + nCursor*sizeof(Cursor*)        /* apCsr */
     );
-    if( !sqlite3ThreadData()->mallocFailed ){
+    if( !sqlite3ThreadDataReadOnly()->mallocFailed ){
       p->aMem = &p->aStack[nStack];
       p->nMem = nMem;
       p->aVar = &p->aMem[nMem];
@@ -890,7 +891,7 @@ int sqlite3VdbeSetColName(Vdbe *p, int idx, const char *zName, int N){
   int rc;
   Mem *pColName;
   assert( idx<(2*p->nResColumn) );
-  if( sqlite3ThreadData()->mallocFailed ) return SQLITE_NOMEM;
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ) return SQLITE_NOMEM;
   assert( p->aColName!=0 );
   pColName = &(p->aColName[idx]);
   if( N==P3_DYNAMIC || N==P3_STATIC ){
@@ -1153,7 +1154,7 @@ int sqlite3VdbeHalt(Vdbe *p){
   int i;
   int (*xFunc)(Btree *pBt) = 0;  /* Function to call on each btree backend */
 
-  if( sqlite3ThreadData()->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     p->rc = SQLITE_NOMEM;
   }
 
diff --git a/src/vdbemem.c b/src/vdbemem.c
index e3463352f..d0cadbddd 100644
--- a/src/vdbemem.c
+++ b/src/vdbemem.c
@@ -756,7 +756,7 @@ const void *sqlite3ValueText(sqlite3_value* pVal, u8 enc){
   }else if( !(pVal->flags&MEM_Blob) ){
     sqlite3VdbeMemStringify(pVal, enc);
   }
-  assert(pVal->enc==enc || sqlite3ThreadData()->mallocFailed);
+  assert(pVal->enc==enc || sqlite3ThreadDataReadOnly()->mallocFailed);
   return (const void *)(pVal->enc==enc ? (pVal->z) : 0);
 }
 
diff --git a/src/where.c b/src/where.c
index e427e62c1..bcb342ff9 100644
--- a/src/where.c
+++ b/src/where.c
@@ -16,7 +16,7 @@
 ** so is applicable.  Because this module is responsible for selecting
 ** indices, you might also think of this module as the "query optimizer".
 **
-** $Id: where.c,v 1.193 2006/01/10 17:58:23 danielk1977 Exp $
+** $Id: where.c,v 1.194 2006/01/11 21:41:22 drh Exp $
 */
 #include "sqliteInt.h"
 
@@ -567,7 +567,7 @@ static void exprAnalyze(
   int nPattern;
   int isComplete;
 
-  if( sqlite3ThreadData()->mallocFailed ) return;
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ) return;
   prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
   if( pExpr->op==TK_IN ){
     assert( pExpr->pRight==0 );
@@ -1438,7 +1438,7 @@ WhereInfo *sqlite3WhereBegin(
   ** return value.
   */
   pWInfo = sqliteMalloc( sizeof(WhereInfo) + pTabList->nSrc*sizeof(WhereLevel));
-  if( sqlite3ThreadData()->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     goto whereBeginNoMem;
   }
   pWInfo->pParse = pParse;
@@ -1462,7 +1462,7 @@ WhereInfo *sqlite3WhereBegin(
     createMask(&maskSet, pTabList->a[i].iCursor);
   }
   exprAnalyzeAll(pTabList, &maskSet, &wc);
-  if( sqlite3ThreadData()->mallocFailed ){
+  if( sqlite3ThreadDataReadOnly()->mallocFailed ){
     goto whereBeginNoMem;
   }