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    <title>MongoDB Jira</title>
    <link>https://jira.mongodb.org</link>
    <description>This file is an XML representation of an issue</description>
    <language>en-us</language>    <build-info>
        <version>9.7.1</version>
        <build-number>970001</build-number>
        <build-date>13-04-2023</build-date>
    </build-info>


<item>
            <title>[CXX-1184] Prevent misuse of client temporaries</title>
                <link>https://jira.mongodb.org/browse/CXX-1184</link>
                <project id="11980" key="CXX">C++ Driver</project>
                    <description>&lt;p&gt;(Original title: &quot;find/cursor documentation doesn&apos;t warn about client lifetime&quot;)&lt;/p&gt;

&lt;p&gt;From &lt;a href=&quot;https://groups.google.com/forum/#!topic/mongodb-user/girvbR21AzM:&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://groups.google.com/forum/#!topic/mongodb-user/girvbR21AzM:&lt;/a&gt;&lt;/p&gt;

&lt;blockquote&gt;
&lt;p/&gt;
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					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;  margin-top: 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;auto c = pool-&amp;gt;acquire()-&amp;gt;database()[collection].find({});&lt;/span&gt;&lt;/pre&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   margin-bottom: 10px;  width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;// loop c&lt;/span&gt;&lt;/pre&gt;
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&lt;p/&gt;

&lt;p&gt;pool-&amp;gt;acquire() returns an unique_ptr, and cursor object c rely on this unique_ptr, before c destroy, unique_ptr need stay.&lt;br/&gt;
This is dangerous, however user may never find this bug until they release into production env.&lt;br/&gt;
Maybe add an assert to check this, let it crash early.&lt;/p&gt;&lt;/blockquote&gt;</description>
                <environment></environment>
        <key id="342910">CXX-1184</key>
            <summary>Prevent misuse of client temporaries</summary>
                <type id="2" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14711&amp;avatarType=issuetype">New Feature</type>
                                            <priority id="3" iconUrl="https://jira.mongodb.org/images/icons/priorities/major.svg">Major - P3</priority>
                        <status id="6" iconUrl="https://jira.mongodb.org/images/icons/statuses/closed.png" description="The issue is considered finished, the resolution is correct. Issues which are closed can be reopened.">Closed</status>
                    <statusCategory id="3" key="done" colorName="success"/>
                                    <resolution id="9">Done</resolution>
                                        <assignee username="-1">Unassigned</assignee>
                                    <reporter username="david.golden@mongodb.com">David Golden</reporter>
                        <labels>
                    </labels>
                <created>Thu, 5 Jan 2017 14:15:09 +0000</created>
                <updated>Tue, 27 Mar 2018 23:33:44 +0000</updated>
                            <resolved>Thu, 8 Mar 2018 15:21:48 +0000</resolved>
                                                    <fixVersion>3.3.0-rc0</fixVersion>
                                    <component>Documentation</component>
                                        <votes>0</votes>
                                    <watches>4</watches>
                                                                                                                <comments>
                            <comment id="1847306" author="serjaimelannister" created="Tue, 27 Mar 2018 23:33:14 +0000"  >&lt;p&gt;I&apos;m sorry, Please ignore my previous comments. I think I have fixed my problem.&lt;/p&gt;

&lt;p&gt;the issue is that I have a main project which includes another sub project with git submodule.&lt;/p&gt;

&lt;p&gt;within both the main project and the sub project, there are MongoDb wrappers defined using the same name.&lt;/p&gt;

&lt;p&gt;This must have confused the compiler/linker and caused some thing uninitialized. I have renamed one of the wrapper to use a different name and the issue seemed to be fixed.&lt;/p&gt;</comment>
                            <comment id="1847237" author="acm" created="Tue, 27 Mar 2018 22:26:02 +0000"  >&lt;p&gt;It is impossible to define copy or copy-assignment operators for that class exactly because it contains a unique_ptr. Similarly, the compiler generated move constructor and move assignment operator should be automatically correct.&lt;/p&gt;

&lt;p&gt;I suspect something else is going wrong.&lt;/p&gt;

&lt;p&gt;As this ticket is closed, I&apos;d prefer that you do one of the following so we can continue to investigate:&lt;/p&gt;
&lt;ul class=&quot;alternate&quot; type=&quot;square&quot;&gt;
	&lt;li&gt;Email mongodb-user with a reproducing test case and details on your platform, C++ Driver version, and toolchain&lt;/li&gt;
	&lt;li&gt;Open a question on stackoverflow with the mongo-cxx-driver tag, providing the same info&lt;/li&gt;
	&lt;li&gt;Open a new ticket in the CXX project on JIRA, providing the same info&lt;/li&gt;
&lt;/ul&gt;


&lt;p&gt;That will make it easier for us to assign someone to work with you to understand the root cause of this issue.&lt;/p&gt;
</comment>
                            <comment id="1847232" author="serjaimelannister" created="Tue, 27 Mar 2018 22:18:00 +0000"  >&lt;p&gt;it is a crash, a segmentation fault caused by assignment of the object mongocxx::pool::entry&lt;/p&gt;

&lt;p&gt;the issue is because of the unique pointer used in that class:&lt;/p&gt;

&lt;p&gt;should a copy constructor and a operator= be defined for this class?&lt;/p&gt;

&lt;p/&gt;
&lt;div id=&quot;syntaxplugin&quot; class=&quot;syntaxplugin&quot; style=&quot;border: 1px dashed #bbb; border-radius: 5px !important; overflow: auto; max-height: 30em;&quot;&gt;
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					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;  margin-top: 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;        using unique_client = std::unique_ptr&amp;lt;client, std::function&amp;lt;void MONGOCXX_CALL(client*)&amp;gt;&amp;gt;;&lt;/span&gt;&lt;/pre&gt;
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					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&amp;nbsp;&lt;/pre&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;        MONGOCXX_PRIVATE explicit entry(unique_client);&lt;/span&gt;&lt;/pre&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   margin-bottom: 10px;  width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;        unique_client _client;&lt;/span&gt;&lt;/pre&gt;
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&lt;/div&gt;
&lt;p/&gt;</comment>
                            <comment id="1846979" author="acm" created="Tue, 27 Mar 2018 19:20:51 +0000"  >&lt;p&gt;&lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=serjaimelannister&quot; class=&quot;user-hover&quot; rel=&quot;serjaimelannister&quot;&gt;serjaimelannister&lt;/a&gt; - What is the error message your compiler emits?&lt;/p&gt;</comment>
                            <comment id="1846973" author="serjaimelannister" created="Tue, 27 Mar 2018 19:17:35 +0000"  >&lt;p&gt;The change for this bug, commit &lt;a href=&quot;https://github.com/mongodb/mongo-cxx-driver/commit/423d3b9613c5fa0c95d649f528c064107df86ef0&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo-cxx-driver/commit/423d3b9613c5fa0c95d649f528c064107df86ef0&lt;/a&gt;&lt;/p&gt;

&lt;p&gt;seems to break my code.&lt;/p&gt;

&lt;p&gt;In my code, I have a mongodb wrapper class, in which there is a getClient() that returns a client to use.&lt;/p&gt;

&lt;p&gt;the function is defined:&lt;/p&gt;

&lt;p/&gt;
&lt;div id=&quot;syntaxplugin&quot; class=&quot;syntaxplugin&quot; style=&quot;border: 1px dashed #bbb; border-radius: 5px !important; overflow: auto; max-height: 30em;&quot;&gt;
&lt;table cellspacing=&quot;0&quot; cellpadding=&quot;0&quot; border=&quot;0&quot; width=&quot;100%&quot; style=&quot;font-size: 1em; line-height: 1.4em !important; font-weight: normal; font-style: normal; color: black;&quot;&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;  margin-top: 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;mongocxx::pool::entry MongodbManager::getClient()&lt;/span&gt;&lt;/pre&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;{&lt;/span&gt;&lt;/pre&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    return m_pool.acquire();&lt;/span&gt;&lt;/pre&gt;
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					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   margin-bottom: 10px;  width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;}&lt;/span&gt;&lt;/pre&gt;
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&lt;/div&gt;
&lt;p/&gt;
&lt;p&gt;the client, as returned by pool.acquire() is not returnable because of the unique_ptr member.&lt;/p&gt;
</comment>
                            <comment id="1837517" author="xgen-internal-githook" created="Sat, 17 Mar 2018 17:49:32 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{&apos;email&apos;: &apos;jesse@mongodb.com&apos;, &apos;name&apos;: &apos;A. Jesse Jiryu Davis&apos;, &apos;username&apos;: &apos;ajdavis&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/CXX-1184&quot; title=&quot;Prevent misuse of client temporaries&quot; class=&quot;issue-link&quot; data-issue-key=&quot;CXX-1184&quot;&gt;&lt;del&gt;CXX-1184&lt;/del&gt;&lt;/a&gt; Mark pool::entry for export&lt;br/&gt;
Branch: master&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo-cxx-driver/commit/1c4bbc84149f750ddc1dc3300d9108cc8638910d&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo-cxx-driver/commit/1c4bbc84149f750ddc1dc3300d9108cc8638910d&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="1827269" author="xgen-internal-githook" created="Thu, 8 Mar 2018 15:22:04 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{&apos;email&apos;: &apos;jesse@mongodb.com&apos;, &apos;name&apos;: &apos;A. Jesse Jiryu Davis&apos;, &apos;username&apos;: &apos;ajdavis&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/CXX-1184&quot; title=&quot;Prevent misuse of client temporaries&quot; class=&quot;issue-link&quot; data-issue-key=&quot;CXX-1184&quot;&gt;&lt;del&gt;CXX-1184&lt;/del&gt;&lt;/a&gt; prohibit calling cursor-returning fns on temporaries&lt;br/&gt;
Branch: master&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo-cxx-driver/commit/423d3b9613c5fa0c95d649f528c064107df86ef0&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo-cxx-driver/commit/423d3b9613c5fa0c95d649f528c064107df86ef0&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="1815238" author="jesse" created="Sat, 24 Feb 2018 23:41:32 +0000"  >&lt;p&gt;Demo (this segfaults):&lt;/p&gt;
&lt;p/&gt;
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					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;  margin-top: 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#include &amp;lt;iostream&amp;gt;&lt;/span&gt;&lt;/pre&gt;
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					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#include &amp;lt;bsoncxx/json.hpp&amp;gt;&lt;/span&gt;&lt;/pre&gt;
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					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#include &amp;lt;mongocxx/pool.hpp&amp;gt;&lt;/span&gt;&lt;/pre&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#include &amp;lt;mongocxx/client.hpp&amp;gt;&lt;/span&gt;&lt;/pre&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;#include &amp;lt;mongocxx/instance.hpp&amp;gt;&lt;/span&gt;&lt;/pre&gt;
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					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;int main() {&lt;/span&gt;&lt;/pre&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    mongocxx::instance inst{};&lt;/span&gt;&lt;/pre&gt;
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						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    auto pool = new mongocxx::pool{mongocxx::uri{&quot;mongodb://localhost/?minPoolSize=1&quot;}};&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    {&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;        auto c = pool-&amp;gt;acquire()-&amp;gt;database(&quot;db&quot;)[&quot;collection&quot;].find({});&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;        auto tmp = pool-&amp;gt;acquire(); // the cursor&apos;s client&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;        auto tmp2 = pool-&amp;gt;acquire(); // another client&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;        tmp = nullptr; // return the cursor&apos;s client&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;        tmp2 = nullptr; // return the other client, the cursor&apos;s client is destroyed&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&amp;nbsp;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;        for (auto &amp;amp;&amp;amp;d : c) {&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;            std::cout &amp;lt;&amp;lt; bsoncxx::to_json(d) &amp;lt;&amp;lt; std::endl;&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;        }&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    }&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&amp;nbsp;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    delete pool;&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&amp;nbsp;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    return 0;&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   margin-bottom: 10px;  width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;}&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
			&lt;/tbody&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;p/&gt;
&lt;p&gt;Swapping the line &lt;tt&gt;tmp = nullptr;&lt;/tt&gt; with the next line allows the program to complete.&lt;/p&gt;</comment>
                            <comment id="1470213" author="acm" created="Thu, 5 Jan 2017 16:38:19 +0000"  >&lt;p&gt;My point was more that the expression as written contains two bugs, not just one.&lt;/p&gt;

&lt;p&gt;As for lifecycle contracts, this was extensively debated during the design phase of the C&amp;#43;&amp;#43;11 driver, and the conclusion was that we shouldn&apos;t try to guarantee them - C&amp;#43;&amp;#43; isn&apos;t Java, and managing lifetimes to honor contracts is an expected part of using the language and its associated libraries. What we can, and should, do, is document those constraints and attempt to make apparently safe idioms not compile. We can do that for above case by disallowing invocation of &apos;find&apos; or other cursor returning objects on collection temporaries.&lt;/p&gt;

&lt;p&gt;Note also that it is almost certainly possible to build a set of shared pointer managed types that sit above client/database/collection/cursor and do the right thing.&lt;/p&gt;</comment>
                            <comment id="1470201" author="david.golden" created="Thu, 5 Jan 2017 16:29:46 +0000"  >&lt;p&gt;Note: per Slack conversation, &lt;tt&gt;mongoc_cursor_t&lt;/tt&gt; only really depends on &lt;tt&gt;mongoc_client_t&lt;/tt&gt;.  We should wait until &lt;a href=&quot;https://jira.mongodb.org/browse/CDRIVER-1980&quot; title=&quot;Incorrect lifecycle documentation needs review&quot; class=&quot;issue-link&quot; data-issue-key=&quot;CDRIVER-1980&quot;&gt;&lt;del&gt;CDRIVER-1980&lt;/del&gt;&lt;/a&gt; (fixing lifecycle docs) is done before finalizing a solution.&lt;/p&gt;</comment>
                            <comment id="1470196" author="david.golden" created="Thu, 5 Jan 2017 16:20:15 +0000"  >&lt;p&gt;From &lt;a href=&quot;http://mongoc.org/libmongoc/current/mongoc_collection_t.html:&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;http://mongoc.org/libmongoc/current/mongoc_collection_t.html:&lt;/a&gt;&lt;/p&gt;

&lt;blockquote&gt;&lt;p&gt;It is an error to call mongoc_collection_destroy() on a collection that has operations pending. It is required that you release mongoc_cursor_t structures before calling mongoc_collection_destroy().&lt;/p&gt;&lt;/blockquote&gt;

&lt;p&gt;From &lt;a href=&quot;http://mongoc.org/libmongoc/current/mongoc_database_t.html&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;http://mongoc.org/libmongoc/current/mongoc_database_t.html&lt;/a&gt;&lt;/p&gt;

&lt;blockquote&gt;&lt;p&gt;It is an error to call mongoc_database_destroy() on a database that has operations pending. It is required that you release mongoc_cursor_t structures before calling mongoc_database_destroy.&lt;/p&gt;&lt;/blockquote&gt;

&lt;p&gt;From &lt;a href=&quot;http://mongoc.org/libmongoc/current/mongoc_client_t.html:&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;http://mongoc.org/libmongoc/current/mongoc_client_t.html:&lt;/a&gt;&lt;/p&gt;

&lt;blockquote&gt;&lt;p&gt;It is an error to call mongoc_client_destroy on a client that has operations pending. It is required that you release mongoc_collection_t and mongoc_database_t structures before calling mongoc_client_destroy.&lt;/p&gt;&lt;/blockquote&gt;

&lt;p&gt;We need to think more broadly how to guarantee those lifecycle contracts because right now we don&apos;t guarantee the destruction order that libmongoc mandates.  While I know we&apos;ve avoided shared pointers, having everything reference count upwards would certainly do the trick.  That has a cost, sure, but I&apos;m not sure how else we can satisfy the contract in code.  We could document the same constraints for our users, but then we&apos;re sort of doing RAII in name only, as they still need to manage destruction order manually.&lt;/p&gt;

&lt;p&gt;Other ideas?&lt;/p&gt;</comment>
                            <comment id="1470094" author="acm" created="Thu, 5 Jan 2017 14:42:01 +0000"  >&lt;p&gt;Is it legal to use the cursor result of mongocxx::collection::find after the mongocxx::collection has been destroyed? If not, there may actually be two bugs in the above statement, but it is not clear from the underlying mongoc docs whether or not it is OK.&lt;/p&gt;

&lt;p&gt;Independently of that, it may in fact be possible to make the above bug illegal, but returning a proxy object rather than a bare unique_ptr from mongocxx::pool::acquire. The proxy object would implement operator-&amp;gt; but it would have an explicitly deleted operator-&amp;gt; for the &amp;amp;&amp;amp; case, much like mongocxx::client::database.&lt;/p&gt;</comment>
                    </comments>
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