nMax can be zero and subtracting 1 from an unsigned zero produces undesirable results (CVS 6506)

FossilOrigin-Name: a117d82dad82bc372bc1e3f1adb9540c1accf851

manifest

@@ -1,5 +1,5 @@
-C Change\sthe\ssqlite3_bind_value()\simplementation\sto\suse\sa\sdefault\sbranch\son\nthe\stype\sswitch\sso\sthat\sthere\sare\sno\suntested\sjumps\sin\sthe\sswitch.\s(CVS\s6505)
-D 2009-04-14T12:58:20
+C nMax\scan\sbe\szero\sand\ssubtracting\s1\sfrom\san\sunsigned\szero\sproduces\sundesirable\sresults\s(CVS\s6506)
+D 2009-04-14T18:44:39
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in 583e87706abc3026960ed759aff6371faf84c211
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -148,7 +148,7 @@ F src/pager.h 0c9f3520c00d8a3b8e792ca56c9a11b6b02b4b0f
 F src/parse.y b7e4341b21736a90b952aa6bb663ec98529b778e
 F src/pcache.c 395f752a13574120bd7513a400ba02a265aaa76d
 F src/pcache.h 9b927ccc5a538e31b4c3bc7eec4f976db42a1324
-F src/pcache1.c f587565f4ba0fd1772067eaa96814dce761b7a4c
+F src/pcache1.c 35f8601c91c09a1e887a1914ebca07bb5afc7b89
 F src/pragma.c c26c16c49a80d03c8597f0e6c7daba53f283428f
 F src/prepare.c 0ad1ba3290e0626aa4e7589ed6ab6af2572875b0
 F src/printf.c ea2d76000cc5f4579d7e9cb2f5460433eec0d384
@@ -717,7 +717,7 @@ F tool/speedtest16.c c8a9c793df96db7e4933f0852abb7a03d48f2e81
 F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
-P 3db0c7980668cf38165add13f833863cd00a0cfe
-R 34f39946bda012d0092593a65918e629
-U drh
-Z 98a6c859bf61c1e15172ad734a5c6432
+P d0a8bd6a53c5da0ac6b88818f82c7f7d330b527a
+R d56036d84dd34b957b5b44bc1a5365cf
+U aswift
+Z d875c935111ab458c0af133f3a6bf1c5

manifest.uuid

@@ -1 +1 @@
-d0a8bd6a53c5da0ac6b88818f82c7f7d330b527a
+a117d82dad82bc372bc1e3f1adb9540c1accf851

src/pcache1.c

@@ -16,7 +16,7 @@
 ** If the default page cache implementation is overriden, then neither of
 ** these two features are available.
 **
-** @(#) $Id: pcache1.c,v 1.10 2009/03/23 04:33:33 danielk1977 Exp $
+** @(#) $Id: pcache1.c,v 1.11 2009/04/14 18:44:39 aswift Exp $
 */
 
 #include "sqliteInt.h"
@@ -527,7 +527,7 @@ static void *pcache1Fetch(sqlite3_pcache *p, unsigned int iKey, int createFlag){
 
   /* Step 4. Try to recycle a page buffer if appropriate. */
   if( pCache->bPurgeable && pcache1.pLruTail && (
-      pCache->nPage>=pCache->nMax-1 || pcache1.nCurrentPage>=pcache1.nMaxPage
+     (pCache->nPage+1>=pCache->nMax) || pcache1.nCurrentPage>=pcache1.nMaxPage
   )){
     pPage = pcache1.pLruTail;
     pcache1RemoveFromHash(pPage);