Clarify the expectations for the behavior of the xFetch method on the

sqlite3_pcache_methods object for the case when the key is zero.

FossilOrigin-Name: b0810ac1b22226a0ffcf73868779d7e98b5d8263

manifest

@@ -1,5 +1,5 @@
-C Fix\sa\sharmless\scompiler\swarning\sin\sfuzzcheck.c
-D 2016-12-30T12:10:48.960
+C Clarify\sthe\sexpectations\sfor\sthe\sbehavior\sof\sthe\sxFetch\smethod\son\sthe\nsqlite3_pcache_methods\sobject\sfor\sthe\scase\swhen\sthe\skey\sis\szero.
+D 2016-12-30T13:55:50.562
 F Makefile.in 41bd4cad981487345c4a84081074bcdb876e4b2e
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc b8ca53350ae545e3562403d5da2a69cec79308da
@@ -375,12 +375,12 @@ F src/os_setup.h 0dbaea40a7d36bf311613d31342e0b99e2536586
 F src/os_unix.c 30e2c43e4955db990e5b5a81e901f8aa74cc8820
 F src/os_win.c cf90abd4e50d9f56d2c20ce8e005aff55d7bd8e9
 F src/os_win.h 7b073010f1451abe501be30d12f6bc599824944a
-F src/pager.c 1c7a2b82b290b85b90f9275ae003f688935f70f9
+F src/pager.c 71881289acefc52888c781cc1d3ea659c311a5da
 F src/pager.h d1e944291030351f362a0a7da9b5c3e34e603e39
 F src/parse.y 29153738a7322054359320eb00b5a4cd44389f20
 F src/pcache.c 51070ec9b8251bbf9c6ea3d35fd96a458752929e
 F src/pcache.h 2cedcd8407eb23017d92790b112186886e179490
-F src/pcache1.c e3967219b2a92b9edcb9324a4ba75009090d3953
+F src/pcache1.c 26a72c84d7ed96d85da7910194d01da9777a3335
 F src/pragma.c 5a23557e490e7ac5afef097efc4b59dce5b482c2
 F src/pragma.h f9b221b2c8949ea941dbee49934299e4ed5af41c
 F src/prepare.c b1140c3d0cf59bc85ace00ce363153041b424b7a
@@ -390,7 +390,7 @@ F src/resolve.c bb070cf5f23611c44ab7e4788803684e385fc3fb
 F src/rowset.c 7b7e7e479212e65b723bf40128c7b36dc5afdfac
 F src/select.c dfb6cadc3dcfba1b1bdbfba62ebba2b4b673413e
 F src/shell.c 6095531aa900decdaa765e0f3993fba7153c92c1
-F src/sqlite.h.in e8e2d108d82647f0a812fdb74accf91c1ec08ddc
+F src/sqlite.h.in c50b91a917b5a78469e0910a539cf84087ba821e
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h 8648034aa702469afb553231677306cc6492a1ae
 F src/sqliteInt.h 2075e22d50833ca2d9956d0b7a6bfb845ad05dd2
@@ -1540,7 +1540,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 3e25ba6e42fba239795a465b8510386a361ee5be
-R cb43d33d19adf32bebd1dfaa0e0b456a
+P 5550e815dd943b15c3b08f0526280bba76976199
+R 40395c430e6a26d64841635be7560ef8
 U drh
-Z 067d360edde333b631fbf0df03bf7c2e
+Z b0285f49e100b02afd5ae0bacab221f8

manifest.uuid

@@ -1 +1 @@
-2842bc60538369f888c7df8365858c910322277d
+b0810ac1b22226a0ffcf73868779d7e98b5d8263

src/pager.c

@@ -5376,7 +5376,11 @@ static int getPageNormal(
   pBase = sqlite3PcacheFetch(pPager->pPCache, pgno, 3);
   if( pBase==0 ){
     pPg = 0;
-    rc = sqlite3PcacheFetchStress(pPager->pPCache, pgno, &pBase);
+    if( pgno==0 ){
+      rc = SQLITE_CORRUPT_BKPT;
+    }else{
+      rc = sqlite3PcacheFetchStress(pPager->pPCache, pgno, &pBase);
+    }
     if( rc!=SQLITE_OK ) goto pager_acquire_err;
     if( pBase==0 ){
       rc = SQLITE_NOMEM_BKPT;
@@ -5400,11 +5404,11 @@ static int getPageNormal(
     /* The pager cache has created a new page. Its content needs to 
     ** be initialized. But first some error checks:
     **
-    ** (1) Minimum page number is 1
-    ** (2) The maximum page number is 2^31
-    ** (3) Never try to fetch the locking page
+    ** (1) The maximum page number is 2^31
+    ** (2) Never try to fetch the locking page
     */
-    if( pgno==0 || pgno>PAGER_MAX_PGNO || pgno==PAGER_MJ_PGNO(pPager) ){
+    assert( pgno>0 );
+    if( pgno>PAGER_MAX_PGNO || pgno==PAGER_MJ_PGNO(pPager) ){
       rc = SQLITE_CORRUPT_BKPT;
       goto pager_acquire_err;
     }

src/pcache1.c

@@ -997,7 +997,7 @@ static PgHdr1 *pcache1FetchNoMutex(
     }else{
       return pPage;
     }
-  }else if( createFlag ){
+  }else if( createFlag && iKey ){
     /* Steps 3, 4, and 5 implemented by this subroutine */
     return pcache1FetchStage2(pCache, iKey, createFlag);
   }else{

src/sqlite.h.in

@@ -7215,7 +7215,8 @@ struct sqlite3_pcache_page {
 ** for each entry in the page cache.
 **
 ** The page to be fetched is determined by the key. ^The minimum key value
-** is 1.  After it has been retrieved using xFetch, the page is considered
+** is 1.  The xFetch() method must return NULL if passed a key of 0.
+** After it has been retrieved using xFetch, the page is considered
 ** to be "pinned".
 **
 ** If the requested page is already in the page cache, then the page cache
@@ -7227,10 +7228,11 @@ struct sqlite3_pcache_page {
 ** <table border=1 width=85% align=center>
 ** <tr><th> createFlag <th> Behavior when page is not already in cache
 ** <tr><td> 0 <td> Do not allocate a new page.  Return NULL.
-** <tr><td> 1 <td> Allocate a new page if it easy and convenient to do so.
-**                 Otherwise return NULL.
+** <tr><td> 1 <td> Allocate a new page if it easy and convenient to do so
+**                 and the key is not zero.  Otherwise return NULL.
 ** <tr><td> 2 <td> Make every effort to allocate a new page.  Only return
-**                 NULL if allocating a new page is effectively impossible.
+**                 NULL if the key is zero or if allocating a new page is 
+**                 effectively impossible.
 ** </table>
 **
 ** ^(SQLite will normally invoke xFetch() with a createFlag of 0 or 1.  SQLite