[waffle] [PATCH (maint-1.4)] wflinfo: Fix glGetStringi on Mali

[Chad Versace]

+Frank

On Wed 19 Nov 2014, Chad Versace wrote:
>On Mali EGL 1.4, you can't obtain non-extension functions (including
>OpenGL ES 3.0 functions) with eglGetProcAddress. You must use dlsym.
>
>This patch carefully avoids breaking glGetStringi on other platforms,
>which may expose glGetStringi dynamically (as in eglGetProcAddress) but
>not statically (as in dlsym).
>
>Fixes #20: https://github.com/waffle-gl/waffle/pull/20
>Fixes: chromium:428061 [https://code.google.com/p/chromium/issues/detail?id=428061]
>See: https://github.com/anholt/libepoxy/issues/21
>Reported-by: Frank Henigman <fjhenigman at chromium.org>
>Cc: Daniel Kurtz <djkurtz at chromium.org>
>Signed-off-by: Chad Versace <chad.versace at linux.intel.com>
>---
>
>Frank or Daniel, could you please validate this patch on Mali? I tested on
>Fedora with Mesa i965.
>
>
>
>
> src/utils/wflinfo.c | 23 ++++++++++++++++++++++-
> 1 file changed, 22 insertions(+), 1 deletion(-)
>
>diff --git a/src/utils/wflinfo.c b/src/utils/wflinfo.c
>index 0b03e55..0907b4b 100644
>--- a/src/utils/wflinfo.c
>+++ b/src/utils/wflinfo.c
>@@ -1037,7 +1037,28 @@ main(int argc, char **argv)
>     if (!glGetString)
>         error_get_gl_symbol("glGetString");
>
>-    glGetStringi = waffle_get_proc_address("glGetStringi");
>+    // Retrieving GL functions is tricky. When glGetStringi is supported, here
>+    // are some boggling variations as of 2014-11-19:
>+    //   - Mali drivers on EGL 1.4 expose glGetStringi statically from
>+    //     libGLESv2 but not dynamically from eglGetProcAddress. The EGL 1.4 spec
>+    //     permits this behavior.
>+    //   - EGL 1.5 requires that eglGetStringi be exposed dynamically through
>+    //     eglGetProcAddress. Exposing statically with dlsym is optional.
>+    //   - Windows requires that glGetStringi be exposed dynamically from
>+    //     wglGetProcAddress. Exposing statically from GetProcAddress (Window's
>+    //     dlsym equivalent) is optional.
>+    //   - Mesa drivers expose glGetStringi statically from libGL and libGLESv2
>+    //     and dynamically from eglGetProcAddress and glxGetProcAddress.
>+    //   - Mac exposes glGetStringi only statically.
>+    //
>+    // Try waffle_dl_sym before waffle_get_proc_address because
>+    // (1) egl/glXProcAddress can return invalid non-null pointers for
>+    // unsupported functions and (2) dlsym returns non-null if and only if the
>+    // library exposes the symbol.
>+    glGetStringi = waffle_dl_sym(opts.dl, "glGetStringi");
>+    if (!glGetStringi) {
>+        glGetStringi = waffle_get_proc_address("glGetStringi");
>+    }
>
>     const struct wflinfo_config_attrs config_attrs = {
>         .api = opts.context_api,
>-- 
>2.1.2.1.g5433a3e
>