[Piglit] [PATCH 2/8] piglit-dispatch: Install waffle procs during dispatch init

[Chad Versace]

On Mon, Jan 13, 2014 at 08:30:16PM +0800, Daniel Kurtz wrote:
> Hi Chad,
> 
> With this patch applied, we don't even get as far as glGetIntegerv(),
> since we can't even resolve "glGetString" to deduce the GL_VERSION in
> piglit_dispatch_default_init()->piglit_dispatch_init()->piglit_get_gl_version().
> 
> # bin/egl-create-context-valid-flag-debug gles3 -auto
> piglit_dispatch_default_init(api:2)
> piglit_dispatch_init(api:2)
> piglit_get_gl_version: calling glGetString(GL_VERSION)
> piglit: error: get_wfl_core_proc failed due to WAFFLE_ERROR_NOT_INITIALIZED
> GetProcAddress failed for "glGetString"
> PIGLIT: {'result': 'fail' }
> 
> Without my patch, however, we were calling the default dispatch resolution path:
> piglit_get_gl_version
>   piglit_dispatch_glGetString
>     stub_glGetString
>       resolve_glGetString
>          get_core_proc
>             get_core_proc_address
>               get_ext_proc_address
>                 glXGetProcAddressARB()
> 
> This kind of works, and glXGetProcAddressARB returns the address of
> glGetString() in libGLso...  However, this is the wrong glGetString()
> function, since we should be finding glGetString() of libGLESv2.so. On
> my system, this glGetString() returns NULL, and since
> piglit_get_gl_version isn't able to handle a NULL version string, so
> the test crashes with a seg fault.
> 
> So, on my system at least, my patch changed these crashing EGL tests
> into failures.  I considered that progress :-).  Of course, if it
> breaks other
> 
> My patch does fixes some of the OpenGL ES 2.0 and 3.0 tests, though,
> since they use the PIGLIT_GL_TEST_CONFIG_{BEGIN, END} macros, which do
> call waffle_init(). So...
> 
> Why aren't the EGL/GLX tests initializing waffle?
> Is it supposed to work already, or is adding waffle support to EGL
> tests still a work in progress?
> What do you recommend to get them working?

Waffle serves mainly as an abstraction layer over the window
system (X11/GLX, X11/EGL, Wayland/EGL, GBM/EGL). Tests for specific
window system API, such as the GLX and EGL tests, need to directly make
GLX or EGL calls. After all, the tests are validating GLX and EGL
extensions, which are inaccessible through Waffle.

In my original plan, before Waffle was integrated into Piglit, the GLX
and EGL tests would not use Waffle at all, because I didn't see a need
for it. But, maybe there is a need now.

I think the best approach to move forward is to add a new function to
libpiglitutil, piglit_egl_dispatch_init(). This will initialize
piglit-dispatch by directly calling piglit_dispatch_init(), as opposed
to piglit_dispatch_default_init(). By directly calling
piglit_dispatch_init(), it can avoid the waffle initialization problem.

However... I tried that approach today without success. I quickly
descended into a neverending pit of linker errors.

To implement piglit_egl_dispatch_init(), libpiglitutil requires that
piglit_dispatch_init() be defined. But piglit_dispatch_init() is defined
in libpiglitutil_gl. libpiglitutil_gl links to libpiglitutil, not the
other way around.

(Quick explanation of library separation: libpiglitutil contains
utilities independent of the GL api, such as EGL utilities.  This
enables EGL tests to use those utilities without linking to libGL*.
Each of libpiglitutil_{gl,gles1,gles2,gles3} links to its corresponding
libGL*.)

So... I moved piglit-dispatch.c from libpiglitutil_${api} to
libpiglitutil. But this also failed, because piglit-dispatch.c requires
that gl_fw be defined. (Like I said, gl_fw should have never leaked into
this file). Each libpiglitutil_${api} defines gl_fw.

So... I fixed the gl_fw linking problem. Which introduced another
linking problem. Which I fixed. Which introduced another... :(

After playing that game for 2 hours, I still have linker errors from
undefined symbols. I plan to continue to work on it, and hopefully
finish it this week. Here's my branch if you wish to follow:

    http://cgit.freedesktop.org/~chadversary/piglit
    branch=fix-egl-dispatch

I'll keep you updated.