Mesa (master): util/u_draw: Skip rendering instead of aborting when excessive number of instances is found .

[Jose Fonseca]

Module: Mesa
Branch: master
Commit: 4da0cb83ab6d82ba3cf011bb3b9b012bd27f7bfc
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=4da0cb83ab6d82ba3cf011bb3b9b012bd27f7bfc

Author: José Fonseca <jfonseca at vmware.com>
Date:   Fri Nov 16 17:57:38 2012 +0000

util/u_draw: Skip rendering instead of aborting when excessive number of instances is found.

This is a temporary hack. I believe the only way of properly fixing this
is to check buffer overflow just before fetching based on addresses,
instead of number of vertices/instances. This change simply allows tests
that stress buffer overflows to complete without asserting, and should
not affect valid rendering.

Reviewed-by: Brian Paul <brianp at vmware.com>

---

 src/gallium/auxiliary/util/u_draw.c |   11 +++++++++--
 1 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/gallium/auxiliary/util/u_draw.c b/src/gallium/auxiliary/util/u_draw.c
index 5b3c412..83d9284 100644
--- a/src/gallium/auxiliary/util/u_draw.c
+++ b/src/gallium/auxiliary/util/u_draw.c
@@ -108,8 +108,15 @@ util_draw_max_index(
          else {
             /* Per-instance data. Simply make sure the state tracker didn't
              * request more instances than those that fit in the buffer */
-            assert((info->start_instance + info->instance_count)/element->instance_divisor
-                   <= (buffer_max_index + 1));
+            if ((info->start_instance + info->instance_count)/element->instance_divisor
+                > (buffer_max_index + 1)) {
+               /* FIXME: We really should stop thinking in terms of maximum
+                * indices/instances and simply start clamping against buffer
+                * size. */
+               debug_printf("%s: too many instances for vertex buffer\n",
+                            __FUNCTION__);
+               return 0;
+            }
          }
       }
    }