[Mesa-dev] [Bug 60086] New: Wayland platform backend crashes if there's no back buffer during dri2_swap_buffers

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=60086

          Priority: medium
            Bug ID: 60086
          Assignee: mesa-dev at lists.freedesktop.org
           Summary: Wayland platform backend crashes if there's no back
                    buffer during dri2_swap_buffers
          Severity: normal
    Classification: Unclassified
                OS: Linux (All)
          Reporter: antognolli at gmail.com
          Hardware: x86-64 (AMD64)
            Status: NEW
           Version: unspecified
         Component: Other
           Product: Mesa

Created attachment 73945
  --> https://bugs.freedesktop.org/attachment.cgi?id=73945&action=edit
Swap buffer when a segv happens.

When using the Wayland platform backend of Mesa, if there's no call to any
rendering/drawing function, there will be no back buffer present (it should be
NULL). This causes any call to dri2_swap_buffers to segfault, since it accesses
dri2_surf->back->age.

The egl semantics is that the back buffer is undefined at this situation, maybe
presenting only garbage when the swap buffer is done, but it should not crash.

This segfault behavior was reproduced when using the Wayland backend of EFL,
and a test program was written with a window and a canvas, without any objects
on it. It would trigger a swap buffer but no call was done to allocate a back
buffer.

There's a backtrace attached to this bug that shows where the error happens.

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