[osg-users] setGLExtensionFuncPtr priority

[Voerman, L.]

Hi Robert,
maybe this helps: glXGetProcAddressNeverReturnsNULL
<https://dri.freedesktop.org/wiki/glXGetProcAddressNeverReturnsNULL/>
The text in the link states that the nvidia libGL does return NULL, but
that is evidently not true anymore.
I get a pointer for s_glXGetProcAddressARB("RandomString") on debian 9.5 /
nvidia driver 387.22

Regards, Laurens.

On Tue, Aug 28, 2018 at 10:57 AM Robert Osfield <robert.osfield at gmail.com>
wrote:

> We are entering a bit of twilight zone.... to
> osg::getGLExtensionFuncPtr() I added the follow debug output to the
> linux code path:
>
>         static GetProcAddressARBProc s_glXGetProcAddressARB =
> convertPointerType<GetProcAddressARBProc, void*>(dlsym(0,
> "glXGetProcAddressARB"));
>         if (s_glXGetProcAddressARB)
>         {
>             OSG_NOTICE<<"    s_glXGetProcAddressARB("<<funcName<<") =
> "<<(s_glXGetProcAddressARB)(funcName)<<std::endl;
>             OSG_NOTICE<<"
> convertPointerType(s_glXGetProcAddressARB("<<funcName<<")) =
> "<<convertPointerType<void*,
> __GLXextFuncPtr>((s_glXGetProcAddressARB)(funcName))<<std::endl;
>             OSG_NOTICE<<"    dlsym(0, "<<funcName<<") = "<<dlsym(0,
> funcName)<<std::endl;
>
>             return convertPointerType<void*,
> __GLXextFuncPtr>((s_glXGetProcAddressARB)(funcName));
>         }
>
> And the output I get is:
> $ osgbindlesstext  | grep glGetTexture
>     s_glXGetProcAddressARB(glGetTextureHandle) = 1
>     convertPointerType(s_glXGetProcAddressARB(glGetTextureHandle)) =
> convertPointerType(0x7fe1e11bf2e0) 0x7fe1e11bf2e0
>     dlsym(0, glGetTextureHandle) = 0
> getGLExtensionFuncPtr(glGetTextureHandle)
> s_glXGetProcAddressARB(glGetTextureHandle) = 1
>     convertPointerType(s_glXGetProcAddressARB(glGetTextureHandle)) =
> convertPointerType(0x7fe1e11bf2e0) 0x7fe1e11bf2e0
>     dlsym(0, glGetTextureHandle) = 0
> getGLExtensionFuncPtr(glGetTextureHandleARB)
> s_glXGetProcAddressARB(glGetTextureHandleARB) = 1
>     convertPointerType(s_glXGetProcAddressARB(glGetTextureHandleARB))
> = convertPointerType(0x7fe1f27674a0) 0x7fe1f27674a0
>     dlsym(0, glGetTextureHandleARB) = 0x7fe1f3e7a4a0
> getGLExtensionFuncPtr(glGetTextureHandleNV)
> s_glXGetProcAddressARB(glGetTextureHandleNV) = 1
>     convertPointerType(s_glXGetProcAddressARB(glGetTextureHandleNV)) =
> convertPointerType(0x7fe1f27674c0) 0x7fe1f27674c0
>     dlsym(0, glGetTextureHandleNV) = 0x7fe1f3e7a4c0
> getGLExtensionFuncPtr(glGetTextureHandleIMG)
> s_glXGetProcAddressARB(glGetTextureHandleIMG) = 1
>     convertPointerType(s_glXGetProcAddressARB(glGetTextureHandleIMG))
> = convertPointerType(0x7fe1e11bf380) 0x7fe1e11bf380
>     dlsym(0, glGetTextureHandleIMG) = 0
> getGLExtensionFuncPtr(glGetTextureHandleFrog)
> s_glXGetProcAddressARB(glGetTextureHandleFrog) = 1
>     convertPointerType(s_glXGetProcAddressARB(glGetTextureHandleFrog))
> = convertPointerType(0x7fe1e11bf3a0) 0x7fe1e11bf3a0
>     dlsym(0, glGetTextureHandleFrog) = 0
> getGLExtensionFuncPtr(glGetTextureHandleCat)
> s_glXGetProcAddressARB(glGetTextureHandleCat) = 1
>     convertPointerType(s_glXGetProcAddressARB(glGetTextureHandleCat))
> = convertPointerType(0x7fe1e11bf3c0) 0x7fe1e11bf3c0
>     dlsym(0, glGetTextureHandleCat) = 0
>
> So dlsym is working as expected but the s_glXGetProcAddressARB usage
> is problematic when the pointer should be NULL.  More digging to do...
>
> Robert.
> _______________________________________________
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> osg-users at lists.openscenegraph.org
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>
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