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util/draw: replace assertions with conditionals in util_draw_max_index()

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Don't assert/die if a VBO is too small.  Return zero instead.  For
debug builds, emit a warning message since this is an unusual situation
that might indicate that there's a bug in the app.

Note that util_draw_max_index() now returns max_index+1 instead of
max_index.  This lets us return zero to indicate that one of the VBOs
is too small to draw anything.

Fixes a failure with the new piglit vbo-too-small test.

Reviewed-by: José Fonseca <jfonseca@vmware.com>
This commit is contained in:
Brian Paul 2011-11-12 11:50:32 -07:00
parent 94780b5ee6
commit 438d7ac146
2 changed files with 39 additions and 13 deletions
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20
src/gallium/auxiliary/draw/draw_pt.c
View file

@ -422,6 +422,7 @@ draw_vbo(struct draw_context *draw,
{
unsigned reduced_prim = u_reduced_prim(info->mode);
unsigned instance;
unsigned index_limit;
assert(info->instance_count > 0);
if (info->indexed)
@ -470,11 +471,20 @@ draw_vbo(struct draw_context *draw,
if (0)
draw_print_arrays(draw, info->mode, info->start, MIN2(info->count, 20));
draw->pt.max_index = util_draw_max_index(draw->pt.vertex_buffer,
draw->pt.nr_vertex_buffers,
draw->pt.vertex_element,
draw->pt.nr_vertex_elements,
info);
index_limit = util_draw_max_index(draw->pt.vertex_buffer,
draw->pt.nr_vertex_buffers,
draw->pt.vertex_element,
draw->pt.nr_vertex_elements,
info);
if (index_limit == 0) {
/* one of the buffers is too small to do any valid drawing */
debug_warning("draw: VBO too small to draw anything\n");
return;
}
draw->pt.max_index = index_limit - 1;
/*
* TODO: We could use draw->pt.max_index to further narrow

32
src/gallium/auxiliary/util/u_draw.c
View file

@ -33,9 +33,13 @@
/**
* Returns the largest legal index value for the current set of bound vertex
* buffers. Regardless of any other consideration, all vertex lookups need to
* be clamped to 0..max_index to prevent an out-of-bound access.
* Returns the largest legal index value plus one for the current set
* of bound vertex buffers. Regardless of any other consideration,
* all vertex lookups need to be clamped to 0..max_index-1 to prevent
* an out-of-bound access.
*
* Note that if zero is returned it means that one or more buffers is
* too small to contain any valid vertex data.
*/
unsigned
util_draw_max_index(
@ -48,7 +52,7 @@ util_draw_max_index(
unsigned max_index;
unsigned i;
max_index = ~0;
max_index = ~0U - 1;
for (i = 0; i < nr_vertex_elements; i++) {
const struct pipe_vertex_element *element =
&vertex_elements[i];
@ -68,13 +72,25 @@ util_draw_max_index(
assert(format_desc->block.bits % 8 == 0);
format_size = format_desc->block.bits/8;
assert(buffer_size - buffer->buffer_offset <= buffer_size);
if (buffer->buffer_offset >= buffer_size) {
/* buffer is too small */
return 0;
}
buffer_size -= buffer->buffer_offset;
assert(buffer_size - element->src_offset <= buffer_size);
if (element->src_offset >= buffer_size) {
/* buffer is too small */
return 0;
}
buffer_size -= element->src_offset;
assert(buffer_size - format_size <= buffer_size);
if (format_size > buffer_size) {
/* buffer is too small */
return 0;
}
buffer_size -= format_size;
if (buffer->stride != 0) {
@ -95,5 +111,5 @@ util_draw_max_index(
}
}
return max_index;
return max_index + 1;
}