st/mesa: verify that vertex buffer offset isn't negative

For drivers supporting PIPE_CAP_SIGNED_VERTEX_BUFFER_OFFSET the buffer_offset value
will be interpreted as an signed int.

An example of application code causing a negative offset:

            float b[] = { ... }; // 3 float for pos, 3 for color
            glBufferData(GL_ARRAY_BUFFER, ..., b, ...);
            glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), 0);
            glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), &b[3]);
                                                                                ^
                                                                    should be 3 * sizeof(float)

The offset is a ptr so when interpreted as a signed int it can be negative.

This commit adds a verification that (int) buffer_offset is not negative - this would
indicate an application bug. Since it's too late to emit a GL_INVALID_VALUE error,
we replace the negative offset by 0 and emit a debug message.

Signed-off-by: Marek Olšák <[email protected]>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/mesa/state_tracker/st_context.c b/src/mesa/state_tracker/st_context.c
index a94ffe26eba..fada76437b2 100644
--- a/src/mesa/state_tracker/st_context.c
+++ b/src/mesa/state_tracker/st_context.c
@@ -637,6 +637,8 @@ st_create_context_priv(struct gl_context *ctx, struct pipe_context *pipe,
       screen->get_param(screen, PIPE_CAP_INDEP_BLEND_FUNC);
    st->needs_rgb_dst_alpha_override =
       screen->get_param(screen, PIPE_CAP_RGB_OVERRIDE_DST_ALPHA_BLEND);
+   st->has_signed_vertex_buffer_offset =
+      screen->get_param(screen, PIPE_CAP_SIGNED_VERTEX_BUFFER_OFFSET);
 
    st->has_hw_atomics =
       screen->get_shader_param(screen, PIPE_SHADER_FRAGMENT,