[Bug 43969] New: openGL SwapBuffers with NULL context

https://bugs.winehq.org/show_bug.cgi?id=43969

Bug ID: 43969
           Summary: openGL SwapBuffers with NULL context
           Product: Wine
           Version: 2.19
          Hardware: x86
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: winex11.drv
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

A fragment of openGL code works under Windows and crashes under wine staging
2.19 at glxdrv_wglSwapBuffers. This code can be found under the VSTGUI project
(see https://git.io/vFCwl).

The problem in wine is triggered because the library makes a null context
current before the invocation of swapBuffers. As strange as it may be, Windows
is able to render in this condition.
  wglMakeCurrent (deviceContext, 0);
  SwapBuffers (deviceContext);
When I pass a context instead of 0, wine works as well.

This reveals a pair of problems. First, there is a null pointer dereference in
wgl_SwapBuffers. ctx->hdc is an invalid access because of the null context (I
have added the `&& ctx` check).
    if (escape.gl_drawable && ctx) ExtEscape( ctx->hdc, X11DRV_ESCAPE,
sizeof(escape), (LPSTR)&escape, 0, NULL );

This change allows the program to run without crash, but the result is no
rendering. My test configuration on Windows was 8.1 with the vmware GL
passthrough driver.

[Bug 43969] openGL SwapBuffers with NULL context

https://bugs.winehq.org/show_bug.cgi?id=43969

JP Cimalando  changed:

What    |Removed                     |Added
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                 CC|                            |[e-mail]

[Bug 43969] openGL SwapBuffers with NULL context

https://bugs.winehq.org/show_bug.cgi?id=43969

Fabian Maurer  changed:

What    |Removed                     |Added
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                 CC|                            |[e-mail]

--- Comment #1 from Fabian Maurer  ---
Is there a binary to test with?

Btw, you don't need to add yourself into the CC list when you reported the bug,
you already get mails.

[Bug 43969] openGL SwapBuffers with NULL context

https://bugs.winehq.org/show_bug.cgi?id=43969

--- Comment #2 from JP Cimalando  ---
There is a binary, I have just compiled one however it's a Vst plugin, not the
easiest thing to debug. But it can reproduce this bug, which took me some
tedious time to trace.
I have tried to reproduce the bug in a small program, but couldn't, so the
particular context must be important. I have made a debug version which has two
dlls: a working one and a crashing one with null context. I load this in
dssi-vst on Linux, Hermann Seib's vsthost on Windows.

[Bug 43969] openGL SwapBuffers with NULL context

https://bugs.winehq.org/show_bug.cgi?id=43969

--- Comment #3 from JP Cimalando  ---
Created attachment 59623
  --> https://bugs.winehq.org/attachment.cgi?id=59623
binaries for testing

[Bug 43969] openGL SwapBuffers with NULL context

https://bugs.winehq.org/show_bug.cgi?id=43969

joaopa  changed:

What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |[e-mail]

--- Comment #4 from joaopa  ---
Does the bug still occur with wine-4.9?

[Bug 43969] openGL SwapBuffers with NULL context

https://bugs.winehq.org/show_bug.cgi?id=43969

--- Comment #5 from JP Cimalando  ---
Tried in both wine 9.4 and 9.4 staging, it's not resolved.
The original dll still crashes, and the workaround dll still works.

[Bug 43969] openGL SwapBuffers with NULL context

https://bugs.winehq.org/show_bug.cgi?id=43969

--- Comment #6 from JP Cimalando  ---
Created attachment 64671
  --> https://bugs.winehq.org/attachment.cgi?id=64671
Backtrace from dssi-vst using Wine 4.9

[Bug 43969] openGL SwapBuffers with NULL context

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=43969

--- Comment #7 from joaopa  ---
Does the bug still occur with wine-6.5?