[vlc-devel] [PATCH] opengl: api: drain error in case of error

[Romain Vimont]

On Wed, Jan 27, 2021 at 07:37:56PM +0200, Rémi Denis-Courmont wrote:
> Le keskiviikkona 27. tammikuuta 2021, 19.24.34 EET Romain Vimont a écrit :
> > Le 27 janvier 2021 18:13:45 GMT+01:00, Alexandre Janniaux 
> <ajanni at videolabs.io> a écrit :
> > >Otherwise, the error might be detected afterwards in an unrelated part
> > >of the code, leading to potential failure or assertion depending on the
> > >compilation options.
> > >
> > >Indeed, an OpenGL call can lead to multiple errors and glGetError must
> > >be called in loop, as mentioned by the documentation.
> > >
> > >https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glGetError.xhtml
> > >
> > >> To allow for distributed implementations, there may be several error
> > >> flags. If any single error flag has recorded an error, the value of
> > >> that flag is returned and that flag is reset to GL_NO_ERROR when
> > >> glGetError is called. If more than one flag has recorded an error,
> > >> glGetError returns and clears an arbitrary error flag value. Thus,
> > >> glGetError should always be called in a loop, until it returns
> > >> GL_NO_ERROR, if all error flags are to be reset.
> > >
> > >---
> > >
> > > modules/video_output/opengl/gl_api.c | 4 ++++
> > > 1 file changed, 4 insertions(+)
> > >
> > >diff --git a/modules/video_output/opengl/gl_api.c
> > >b/modules/video_output/opengl/gl_api.c
> > >index 1264dde2a1..d990493832 100644
> > >--- a/modules/video_output/opengl/gl_api.c
> > >+++ b/modules/video_output/opengl/gl_api.c
> > >@@ -163,6 +163,10 @@ vlc_gl_api_Init(struct vlc_gl_api *api, vlc_gl_t
> > >*gl)
> > >
> > >      */
> > >     
> > >     api->supports_multisample = version >= 3 && error == GL_NO_ERROR;
> > >
> > >+    /* Drain the errors before continuing. */
> > >+    while (error != GL_NO_ERROR)
> > 
> > Calling it once should be sufficient, isn't it?
> 
> The quoted paragraph implies otherwise. (And don't ask me.)

Yes, sorry, I replied before reading the whole message. Sorry for the
noise.