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POWhy is this simple libpqxx code leaking memory?
 

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  1. POWhy is this simple libpqxx code leaking memory?
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    <p>Recently I wrote an application that accesses a Postgres DB via libpqxx, and it leaks memory badly. Even this simple test program, which is based on the example at <a href="http://pqxx.org/devprojects/libpqxx/doc/4.0/html/Reference/a00001.html" rel="nofollow">http://pqxx.org/devprojects/libpqxx/doc/4.0/html/Reference/a00001.html</a> leaks like no tomorrow.</p> <p>(Edit: I added calls to commit() and clear() in response to suggestions. Same leakiness.)</p> <pre><code>#include &lt;iostream&gt; #include &lt;pqxx/pqxx&gt; #include &lt;string&gt; #include &lt;stdio.h&gt; int main() { try { pqxx::connection c("user=postgres"); int i = 0; while(true) { pqxx::work w(c); pqxx::result r = w.exec("SELECT 1"); w.commit(); i++; if ( i % 1000 == 0 ) printf( "Cycle %d\n", i ); r.clear(); } //while } //try catch (const std::exception &amp;e) { std::cerr &lt;&lt; e.what() &lt;&lt; std::endl; return 1; } //catch } //main </code></pre> <p>After about 75,000 cycles of the loop, top shows 206Mb of virtual memory usage, and it keeps climbing. I ran a similar test program with 5000 cycles through valgrind and got this:</p> <pre><code>==1647== 13,732,155 (219,868 direct, 13,512,287 indirect) bytes in 4,997 blocks are definitely lost in loss record 12 of 12 ==1647== at 0x40060D5: operator new(unsigned int) (vg_replace_malloc.c:214) ==1647== by 0x404C0A9: pqxx::result::result(pg_result*, int, std::string const&amp;, int) (in /usr/lib/libpqxx-4.0.so) ==1647== by 0x40309EF: pqxx::connection_base::make_result(pg_result*, std::string const&amp;) (in /usr/lib/libpqxx-4.0.so) ==1647== by 0x4036D65: ??? (in /usr/lib/libpqxx-4.0.so) ==1647== by 0x405EFD6: pqxx::transaction_base::DirectExec(char const*, int) (in /usr/lib/libpqxx-4.0.so) ==1647== by 0x40416EA: pqxx::dbtransaction::do_exec(char const*) (in /usr/lib/libpqxx-4.0.so) ==1647== by 0x40618FA: pqxx::transaction_base::exec(std::string const&amp;, std::string const&amp;) (in /usr/lib/libpqxx-4.0.so) ==1647== by 0x80498F8: main (dbtest.cpp:21) </code></pre> <p>Any idea what's going on? It's very difficult to accept that a widely used library like libpqxx would have such a severe bug, so what might I be doing wrong here?</p> <p>Configuration details:</p> <ul> <li>OS: Linux 2.6.18-238.el5</li> <li>gcc version 4.4.0 </li> <li>libpqxx 4.0 </li> <li>postgres 9.2</li> </ul> <p>(<strong>Final edit: I found it easier to replace libpqxx with libpq than to keep investigating this memory leak.</strong>)</p>
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    1. USGeoff
    1. USGeoff
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      1. POWhy is this simple libpqxx code leaking memory?
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      1. VTUpMod
    1. COThe examples show a w.commit() is needed after the exec() call. Can you add that and try your test again ?
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      1. POWhy is this simple libpqxx code leaking memory?
      1. USVaibhav Desai
    2. CO@VaibhavDesai Yeah, I tried that but the leak remained. Thanks
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      1. USGeoff
    3. COWhich version do you use (libpqxx, PostgreSql, gcc, ...)? Could you add the `Makefile` please. I could not reproduce your problem using the Debian packages (its 2.6.9, stone age, "old, but stable").
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      1. USBeryllium
 

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