[Mesa-dev] [PATCH] st/mesa: fail to draw instead of asserting in transform feedback

[Dave Airlie]

if we get a request to take the count from feedback, but there
is no buffer to take it from, just draw nothing instead of asserting.

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

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;
       }
    }
 
-- 
2.4.3