[Mesa-dev] [PATCH] egl: link libEGL against the dynamic version of libglapi

[Eric Engestrom]

On Wednesday, 2017-12-27 10:54:56 +0000, Emil Velikov wrote:
> On 18 December 2017 at 16:33, Eric Engestrom <eric.engestrom at imgtec.com> wrote:
> > From: Brendan King <Brendan.King at imgtec.com>
> >
> > DRI modules store the address of the dispatch table in a TLS variable,
> > _glapi_tls_Dispatch.
> >
> > Changes to the way libEGL is built in d884d8d0077c16d459b1 resulted in
> > it being statically linked against libglapi, and thus containing its own
> > copy of _glapi_tls_Dispatch. The result was that some applications would
> > fail to work (e.g. deqp-egl, which dynamically loads libEGL), due to the
> > DRI module storing the dispatch table address in one copy of
> > _glapi_tls_Dispatch, and libEGL obtaining the address from another copy
> > of the variable.
> >
> > This applies to autotools builds with --enable-glx-tls (on by default),
> > and Meson builds (unconditional).
> >
> > Fixes: d884d8d0077c16d459b1 "egl/dri: link directly to libglapi.so"
> > Signed-off-by: Brendan King <Brendan.King at imgtec.com>
> > Signed-off-by: Eric Engestrom <eric.engestrom at imgtec.com>
> > ---
> > This issue was noticed in the PowerVR driver. It's unclear whether other
> > DRI drivers are affected as well.
> > ---
> As the issue described is a Slibtool bug, and the Meson mention it
> misleading I'll amend the commit message and push later on today:

Ack, and sorry for mentioning meson when it was irrelevant :)

> 
> 
> Note: the following happens only when using slibtool.
> Since this is a very serious breakage, we will keep the workaround until a
> better solution is available.
> 
> DRI modules store the address of the dispatch table in a TLS variable,
> _glapi_tls_Dispatch.
> 
> Changes to the way libEGL is built in d884d8d0077c16d459b1 resulted in
> it being statically linked against libglapi, and thus containing its own
> copy of _glapi_tls_Dispatch. The result was that some applications would
> fail to work (e.g. deqp-egl, which dynamically loads libEGL), due to the
> DRI module storing the dispatch table address in one copy of
> _glapi_tls_Dispatch, and libEGL obtaining the address from another copy
> of the variable.
> 
> Fixes: ...
> ...
> Reviewed-by: Emil Velikov <emil.velikov at collabora.com>
> 
> -Emil