Ensure that allocateBtreePage() always clears the MemPage pointer when

it fails due to an I/O or memory allocation error.

FossilOrigin-Name: 09a38bf665902834936d39341627ded88142e6ae

manifest

@@ -1,5 +1,5 @@
-C Move\stwo\sunreachable\sconditionals\sinside\sof\sNEVER()\sor\sassert().
-D 2015-05-29T17:51:16.121
+C Ensure\sthat\sallocateBtreePage()\salways\sclears\sthe\sMemPage\spointer\swhen\nit\sfails\sdue\sto\san\sI/O\sor\smemory\sallocation\serror.
+D 2015-05-29T18:42:11.874
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 994bab32a3a69e0c35bd148b65cde49879772964
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -192,7 +192,7 @@ F src/auth.c b56c78ebe40a2110fd361379f7e8162d23f92240
 F src/backup.c ff743689c4d6c5cb55ad42ed9d174b2b3e71f1e3
 F src/bitvec.c 5eb7958c3bf65210211cbcfc44eff86d0ded7c9d
 F src/btmutex.c 45a968cc85afed9b5e6cf55bf1f42f8d18107f79
-F src/btree.c 5fa5fda8017a223d26b6040062918c4f56ced644
+F src/btree.c 9e837a0e7e35c54bedddf55db906b7902d175078
 F src/btree.h 969adc948e89e449220ff0ff724c94bb2a52e9f1
 F src/btreeInt.h 973a22a6fd61350b454ad614832b1f0a5e25a1e4
 F src/build.c 85a169a0a22f8b80caf513eaf2944d39b979f571
@@ -1281,7 +1281,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 0abfd78ceb09b7f7c27c688c8e3fe93268a13b32
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 00693682d8664fa608ba43684f6376a9bd5b84eb
-R db8d22fad06b4e06987d42eaf1810c23
+P db4e9728fae5f7b0fad6aa0a5be317a7c9e7c417
+R 203c94cd3aa280d28c1c7c31381f4eb0
 U drh
-Z 8cbe618404dd17db82b74657f07aece3
+Z e97ffe3d4cc6b6234faac86c9e55619e

manifest.uuid

@@ -1 +1 @@
-db4e9728fae5f7b0fad6aa0a5be317a7c9e7c417
+09a38bf665902834936d39341627ded88142e6ae

src/btree.c

@@ -5287,8 +5287,7 @@ int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
 ** sqlite3PagerUnref() on the new page when it is done.
 **
 ** SQLITE_OK is returned on success.  Any other return value indicates
-** an error.  *ppPage and *pPgno are undefined in the event of an error.
-** Do not invoke sqlite3PagerUnref() on *ppPage if an error is returned.
+** an error.  *ppPage is set to NULL in the event of an error.
 **
 ** If the "nearby" parameter is not 0, then an effort is made to 
 ** locate a page close to the page number "nearby".  This can be used in an
@@ -5532,6 +5531,7 @@ static int allocateBtreePage(
             rc = sqlite3PagerWrite((*ppPage)->pDbPage);
             if( rc!=SQLITE_OK ){
               releasePage(*ppPage);
+              *ppPage = 0;
             }
           }
           searchList = 0;