c++ - Opening database in invalid location causes memory leak -

i using qt 4.5.3 access sqlite database, :

class db : private boost::noncopyable {  public:   db( qstring file ) : filename( file ),                        realdb( null ),                        theconnectionestablished( false )   {   }   ~db()   {     if ( null != realdb.get() )     {       realdb.reset( null );     }     if ( theconnectionestablished )     {       qsqldatabase::removedatabase( "connname" );     }   }    void open()   {     realdb.reset( new qsqldatabase( qsqldatabase::adddatabase( "qsqlite", "connname" ) ) );     theconnectionestablished = true;      // open db     realdb->setdatabasename( filename );     if ( ! realdb->open() )     {         const qsqlerror dberror = realdb->lasterror();         const qstring errordesc = "error opening database : " + filename +                                   "\ndatabase error : " + dberror.databasetext() +                                   "\ndatabase driver error : " + dberror.drivertext();          // databaseerror class type accepts std::string logging purposes         throw databaseerror( errordesc.tostdstring() );     }   }    const qstring filename;   std::auto_ptr<qsqldatabase> realdb;   bool theconnectionestablished; }; 

now if try test case (i using cxxtest) :

void test_failed_connection() {   db obj( "/" );   ts_assert_throws( obj.open(), databaseerror ); } 

i memory leak reported valgrind :

<error>   <unique>0x5b</unique>   <tid>1</tid>   <kind>leak_definitelylost</kind>   <what>986 (384 direct, 602 indirect) bytes in 1 blocks lost in loss record 23 of 23</what>   <leakedbytes>986</leakedbytes>   <leakedblocks>1</leakedblocks>   <stack>     <frame>       <ip>0x4006d3e</ip>       <obj>/opt/valgrind341/lib/valgrind/x86-linux/vgpreload_memcheck.so</obj>       <fn>malloc</fn>       <dir>/home/slawomir/valgrind-3.4.1/build/valgrind-3.4.1/coregrind/m_replacemalloc</dir>       <file>vg_replace_malloc.c</file>       <line>207</line>     </frame>     <frame>       <ip>0x67fadc4</ip>       <obj>/usr/lib/libsqlite3.so.0.8.6</obj>       <fn>sqlite3_malloc</fn>     </frame>     <frame>       <ip>0x67faf13</ip>       <obj>/usr/lib/libsqlite3.so.0.8.6</obj>     </frame>     <frame>       <ip>0x6816da3</ip>       <obj>/usr/lib/libsqlite3.so.0.8.6</obj>     </frame>     <frame>       <ip>0x68175fd</ip>       <obj>/usr/lib/libsqlite3.so.0.8.6</obj>       <fn>sqlite3_open16</fn>     </frame>     <frame>       <ip>0x40ddef9</ip>       <obj>/usr/lib/qt4/plugins/sqldrivers/libqsqlite.so</obj>     </frame>     <frame>       <ip>0x7f34ae0</ip>       <obj>/usr/lib/libqtsql.so.4.5.2</obj>       <fn>qsqldatabase::open()</fn>     </frame>     </frame>   </stack> </error> 

does know how fix leak?

had browse through qt , sqlite sources ... interesting.

reading manual sqlite3_open16(), http://www.sqlite.org/c3ref/open.html, 1 finds following quote:

whether or not error occurs when opened, resources associated database connection handle should released passing sqlite3_close() when no longer required.

qsqlitedriver::close() seems calling that, http://qt.gitorious.org/qt/qt/blobs/4.7/src/sql/drivers/sqlite/qsql_sqlite.cpp, in case of open having been successful. sqlite's documentation might indicate sqlite3_close() should called either case.

on other hand, http://www.sqlite.org/c3ref/close.html claims no-op if null passed handle (which if open failed). sqlite sourcecode (diy - don't know web source browser interface it) confirms that, returns if called null.

well - nitty-gritty fun of issue...

naively, 1 assumes failure of sqlite3_open*() imply null db handle. according sqlite's sources, read opendatabase() in main.c, that's not true - call can fail still return non-null db handle.

qt looks assumes failure open db connection implies receiving null db handle. that's not sqlite does. documentation clearer, though.

try adding close qsqlitedriver::open() , see if fixes leak. if so, file bug qt guys, , 1 sqlite folks have documentation clarified ;-)