RFR: 8323077: C type error (incompatible function pointer) in X11GLContext.c

[Florian Weimer]

On Sat, 6 Jan 2024 16:42:19 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

> Looks good. In looking at the logs from the GHA run I can see that the warning is gone.
> 
> I note that there is an additional warning on that same line:
> 
> ```
> 2024-01-05T23:04:38.0399339Z /home/runner/work/jfx/jfx/jfx/modules/javafx.graphics/src/main/native-prism-es2/x11/X11GLContext.c:278:61: warning: pointer targets in passing argument 1 of ‘glXGetProcAddress’ differ in signedness [-Wpointer-sign]
> 2024-01-05T23:04:38.0403438Z   278 |             ctxInfo->glXSwapIntervalSGI = glXGetProcAddress("glXSwapIntervalSGI");
> 2024-01-05T23:04:38.0404485Z Successfully started process 'command 'gcc''
> 2024-01-05T23:04:38.0406410Z       |                                                             ^~~~~~~~~~~~~~~~~~~~
> ```
> 
> As long as you are fixing one of the warnings, it would be helpful to fix the other.

I wanted to make the minimal change to fix the build error. I can add the cast to `const GLubyte *`, but I couldn't find an official prototype for the `glXGetProcAddress` function, so I'm not sure if it's consistent across OpenGL implementations.

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PR Comment: https://git.openjdk.org/jfx/pull/1319#issuecomment-1880638934