This bug report was migrated from our old Bugzilla tracker.

Reported in version: 2.0.4
Reported for operating system, platform: All, All

Comments on the original bug report:

On 2016-06-06 06:58:45 +0000, Sylvain wrote:

After creating successfully an opengles2 renderer,
"SDL_GetError" reports anyway the error "Invalid renderer".

Because of the following call stack:

SDL_CreateRenderer()
GLES2_CreateRenderer()
GLES2_ResetState()
GLES2_ActivateRenderer()
GLES2_UpdateViewport()
SDL_GetRendererOutputSize(renderer)
-> it calls CHECK_MAGIC whereas the renderer is not fully created.

On 2016-06-06 07:05:34 +0000, Sylvain wrote:

Although this is a false error, there might be something:

in GLES2_UpdateViewport() :

389 int w, h;
390
391 SDL_GetRendererOutputSize(renderer, &w, &h);
392 data->glViewport(renderer->viewport.x, (h - renderer->viewport.y - renderer->viewport.h),
393 renderer->viewport.w, renderer->viewport.h);

Since "SDL_GetRendererOutputSize" fails, "h" wont be initialized.

On 2016-06-06 07:11:29 +0000, Sylvain wrote:

Indeed, "w" and "h" variable are not initialized.
Valgrind: "Conditional jump or move depends on uninitialised value(s)"

On 2016-06-06 08:05:12 +0000, Sylvain wrote:

opengles1 renderer has the same issue.

On 2016-06-06 08:23:18 +0000, Sylvain wrote:

opengl has not this issue.

What seems different is the "ResetState" function, called at the end of CreateRenderer:

opengl, will directly follow the "UpdateViewport" path:

  if (SDL_GL_GetCurrentContext() == data->context) {
      GL_UpdateViewport(renderer);
  } else {
  SDL_Log("GL_ActivateRenderer..");
      GL_ActivateRenderer(renderer);
  }

opengles and opengles2, will follow the "ActivateRenderer" path:

 if (SDL_CurrentContext == data->context) {
     GLES2_UpdateViewport(renderer);
 } else {
     GLES2_ActivateRenderer(renderer);
 }

On 2016-06-06 20:52:15 +0000, Philipp Wiesemann wrote:

See also bug 3106.

On 2016-06-09 08:04:03 +0000, Sylvain wrote:

Bug 3106 has been marked out "not a bug" because no investigation has been done at that time.

Now that we have more accurate information, there is definitively something to do:

renderer opengles, opengles2: fix the access to un-initialized value.
This is bad, and especially because we don't know how drivers can react to this. It looks like to work on all device, but it may break some very few others.

renderer opengl: review the two lines of code that are different from opengles/opengles2. And if needed, re-impact some modification on opengles/opengles2 !

On 2016-06-09 08:05:07 +0000, Sylvain wrote:

Here's the valgrind output when using opengles renderer:

==15869== Conditional jump or move depends on uninitialised value(s)
==15869== at 0xD2B7A23: ??? (in /usr/lib/nvidia-361/libnvidia-glcore.so.361.42)
==15869== by 0x4EEA4EF: GLES_UpdateViewport (SDL_render_gles.c:690)
==15869== by 0x4EEC791: GLES_ActivateRenderer (SDL_render_gles.c:249)
==15869== by 0x4EEC6A8: GLES_ResetState (SDL_render_gles.c:263)
==15869== by 0x4EE96E9: GLES_CreateRenderer (SDL_render_gles.c:408)
==15869== by 0x4ED4F97: SDL_CreateRenderer_REAL (SDL_render.c:254)
==15869== by 0x4EB1D4F: SDL_CreateRenderer (SDL_dynapi_procs.h:337)
==15869== by 0x402F19: main (main.cpp:29)
==15869== Uninitialised value was created by a stack allocation
==15869== at 0x4EEA400: GLES_UpdateViewport (SDL_render_gles.c:675)

On 2016-07-01 18:16:09 +0000, Sylvain wrote:

Opengles2 renderer can be forced on linux desktop by calling: SDL_SetHint(SDL_HINT_RENDER_DRIVER, "opengles2");

Valgrind log for opengles2 renderer is:

==20889== Conditional jump or move depends on uninitialised value(s)
==20889== at 0xD2B8A23: ??? (in /usr/lib/nvidia-361/libnvidia-glcore.so.361.42)
==20889== by 0x4EF2015: GLES2_UpdateViewport (SDL_render_gles2.c:392)
==20889== by 0x4EF4576: GLES2_ActivateRenderer (SDL_render_gles2.c:342)
==20889== by 0x4EF420E: GLES2_ResetState (SDL_render_gles2.c:1926)
==20889== by 0x4EED448: GLES2_CreateRenderer (SDL_render_gles2.c:2104)
==20889== by 0x4ED4FE7: SDL_CreateRenderer_REAL (SDL_render.c:254)
==20889== by 0x4EB1D9F: SDL_CreateRenderer (SDL_dynapi_procs.h:337)
==20889== by 0x402FA9: main (main.cpp:31)
==20889== Uninitialised value was created by a stack allocation
==20889== at 0x4EF1F20: GLES2_UpdateViewport (SDL_render_gles2.c:377)

On 2016-10-13 15:47:25 +0000, Sam Lantinga wrote:

Fixed, thanks!
https://hg.libsdl.org/SDL/rev/563503b6b4d1