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    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - The xxxx_set_user_data() API cause client data corrupted in listener callbacks"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=100947">100947</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>The xxxx_set_user_data() API cause client data corrupted in listener callbacks
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>Wayland
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>unspecified
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux (All)
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>trivial
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>medium
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>wayland
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>wayland-bugs@lists.freedesktop.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>zhanggyb@163.com
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Hello everyone.
I'm developing a simple C++ GUI toolkit based on wayland, and get stuck with a
weird problem recently.

I created a simple project with minimal code to reproduce this issue for
demonstration: <a href="https://github.com/zhanggyb/set-user-data">https://github.com/zhanggyb/set-user-data</a>

It's a CMake C++ project and use simple C++ structures to wrap wayland client
objects.

My test environment:

    Fedora 25
    Gnome 3.22.2
    wayland-devel-1.12.0-1.fc25.x86_64
    libwayland-client-1.12.0-1.fc25.x86_64

Checkout, build and run:

    $ git clone <a href="https://github.com/zhanggyb/set-user-data">https://github.com/zhanggyb/set-user-data</a>
    $ mkdir build
    $ cd build/
    $ cmake ..
    $ ./demo

Expected result:

    display a rectangle surface on desktop

Actual result:

    assert error will be raised, and the const member variables around wayland
object will be changed in the wl_output or wl_surface listener callbacks, see
<a href="https://github.com/zhanggyb/set-user-data/blob/master/surface.cpp">https://github.com/zhanggyb/set-user-data/blob/master/surface.cpp</a> and
<a href="https://github.com/zhanggyb/set-user-data/blob/master/output.cpp">https://github.com/zhanggyb/set-user-data/blob/master/output.cpp</a>

    Uncomment these 2 lines can avoid assert error:

    <a href="https://github.com/zhanggyb/set-user-data/blob/master/main.cpp:163">https://github.com/zhanggyb/set-user-data/blob/master/main.cpp:163</a>:
output.SetUserData(this);
    <a href="https://github.com/zhanggyb/set-user-data/blob/master/main.cpp:164">https://github.com/zhanggyb/set-user-data/blob/master/main.cpp:164</a>:
surface.SetUserData(this);

I don't know why this happens, it seems the compositor changes the data in
client, or did I use the xxxx_set_user_data() API in the wrong way?

Thanks in advance.</pre>
        </div>
      </p>


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