Mesa (master): st/mesa: don' t draw instead of asserting in transform feedback

[Dave Airlie]

Module: Mesa
Branch: master
Commit: 518abd0bbe1886550b43c62679a2ebd41e8199e9
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=518abd0bbe1886550b43c62679a2ebd41e8199e9

Author: Dave Airlie <airlied at gmail.com>
Date:   Thu Jul 30 20:44:50 2015 +1000

st/mesa: don't draw instead of asserting in transform feedback

if we get a request to take the count from feedback, but there
is no buffer to take it from, just draw as if we got 0 vertices
so nothing.

This fixes this assert killing the ogl conform, and a piglit
test I've sent.

Reviewed-by: Marek Olšák <marek.olsak at amd.com>
Signed-off-by: Dave Airlie <airlied at redhat.com>

---

 src/mesa/state_tracker/st_cb_xformfb.c |    6 ++++--
 src/mesa/state_tracker/st_cb_xformfb.h |    2 +-
 src/mesa/state_tracker/st_draw.c       |    3 ++-
 3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/mesa/state_tracker/st_cb_xformfb.c b/src/mesa/state_tracker/st_cb_xformfb.c
index 07c118e..0708e68 100644
--- a/src/mesa/state_tracker/st_cb_xformfb.c
+++ b/src/mesa/state_tracker/st_cb_xformfb.c
@@ -191,7 +191,6 @@ st_transform_feedback_get_draw_target(struct gl_transform_feedback_object *obj)
       }
    }
 
-   assert(0);
    return NULL;
 }
 
@@ -211,14 +210,17 @@ st_end_transform_feedback(struct gl_context *ctx,
 }
 
 
-void
+bool
 st_transform_feedback_draw_init(struct gl_transform_feedback_object *obj,
                                 struct pipe_draw_info *out)
 {
    struct st_transform_feedback_object *sobj =
          st_transform_feedback_object(obj);
 
+   if (sobj->draw_count == NULL)
+      return false;
    out->count_from_stream_output = sobj->draw_count;
+   return true;
 }
 
 
diff --git a/src/mesa/state_tracker/st_cb_xformfb.h b/src/mesa/state_tracker/st_cb_xformfb.h
index 998c418..fb50ded 100644
--- a/src/mesa/state_tracker/st_cb_xformfb.h
+++ b/src/mesa/state_tracker/st_cb_xformfb.h
@@ -38,7 +38,7 @@ struct pipe_draw_info;
 extern void
 st_init_xformfb_functions(struct dd_function_table *functions);
 
-extern void
+extern bool
 st_transform_feedback_draw_init(struct gl_transform_feedback_object *obj,
                                 struct pipe_draw_info *out);
 
diff --git a/src/mesa/state_tracker/st_draw.c b/src/mesa/state_tracker/st_draw.c
index 66b2f83..bae8096 100644
--- a/src/mesa/state_tracker/st_draw.c
+++ b/src/mesa/state_tracker/st_draw.c
@@ -242,7 +242,8 @@ st_draw_vbo(struct gl_context *ctx,
       /* Transform feedback drawing is always non-indexed. */
       /* Set info.count_from_stream_output. */
       if (tfb_vertcount) {
-         st_transform_feedback_draw_init(tfb_vertcount, &info);
+         if (st_transform_feedback_draw_init(tfb_vertcount, &info) == false)
+            return;
       }
    }