mesa: fix crash in st/mesa after deleting a VAO

This happens when glGetMultisamplefv (or any other non-draw function) is
called, which doesn't invoke the VBO module to update _DrawArrays and
the pointer is invalid at that point.

However st/mesa still dereferences it to setup vertex buffers ==> crash.

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

src/mesa/main/arrayobj.c

@@ -427,6 +427,21 @@ bind_vertex_array(struct gl_context *ctx, GLuint id, GLboolean genRequired)
       }
    }
 
+   if (ctx->Array.DrawMethod == DRAW_ARRAYS) {
+      /* The _DrawArrays pointer is pointing at the VAO being unbound and
+       * that VAO may be in the process of being deleted. If it's not going
+       * to be deleted, this will have no effect, because the pointer needs
+       * to be updated by the VBO module anyway.
+       *
+       * Before the VBO module can update the pointer, we have to set it
+       * to NULL for drivers not to set up arrays which are not bound,
+       * or to prevent a crash if the VAO being unbound is going to be
+       * deleted.
+       */
+      ctx->Array._DrawArrays = NULL;
+      ctx->Array.DrawMethod = DRAW_NONE;
+   }
+
    ctx->NewState |= _NEW_ARRAY;
    _mesa_reference_vao(ctx, &ctx->Array.VAO, newObj);
 

src/mesa/main/mtypes.h

@@ -1640,6 +1640,17 @@ struct gl_vertex_array_object
 };
 
 
+/** Used to signal when transitioning from one kind of drawing method
+ * to another.
+ */
+typedef enum {
+   DRAW_NONE,          /**< Initial value only */
+   DRAW_BEGIN_END,
+   DRAW_DISPLAY_LIST,
+   DRAW_ARRAYS
+} gl_draw_method;
+
+
 /**
  * Vertex array state
  */
@@ -1679,6 +1690,9 @@ struct gl_array_attrib
     * The array pointer is set up only by the VBO module.
     */
    const struct gl_client_array **_DrawArrays; /**< 0..VERT_ATTRIB_MAX-1 */
+
+   /** One of the DRAW_xxx flags, not consumed by drivers */
+   gl_draw_method DrawMethod;
 };
 
 

src/mesa/vbo/vbo_context.h

@@ -57,18 +57,6 @@
 #include "vbo_save.h"
 
 
-/** Used to signal when transitioning from one kind of drawing method
- * to another.
- */
-enum draw_method
-{
-   DRAW_NONE,          /**< Initial value only */
-   DRAW_BEGIN_END,
-   DRAW_DISPLAY_LIST,
-   DRAW_ARRAYS
-};
-
-
 struct vbo_context {
    struct gl_client_array currval[VBO_ATTRIB_MAX];
    
@@ -83,8 +71,6 @@ struct vbo_context {
     * is responsible for initiating any fallback actions required:
     */
    vbo_draw_func draw_prims;
-
-   enum draw_method last_draw_method;
 };
 
 
@@ -122,11 +108,11 @@ get_program_mode( struct gl_context *ctx )
  * that arrays may be changing.
  */
 static inline void
-vbo_draw_method(struct vbo_context *vbo, enum draw_method method)
+vbo_draw_method(struct vbo_context *vbo, gl_draw_method method)
 {
-   if (vbo->last_draw_method != method) {
+   struct gl_context *ctx = vbo->exec.ctx;
-      struct gl_context *ctx = vbo->exec.ctx;
 
+   if (ctx->Array.DrawMethod != method) {
       switch (method) {
       case DRAW_ARRAYS:
          ctx->Array._DrawArrays = vbo->exec.array.inputs;
@@ -142,7 +128,7 @@ vbo_draw_method(struct vbo_context *vbo, enum draw_method method)
       }
 
       ctx->NewDriverState |= ctx->DriverFlags.NewArray;
-      vbo->last_draw_method = method;
+      ctx->Array.DrawMethod = method;
    }
 }
 

src/mesa/vbo/vbo_exec.c

@@ -82,21 +82,6 @@ void vbo_exec_invalidate_state( struct gl_context *ctx, GLuint new_state )
 
    if (!exec->validating && new_state & (_NEW_PROGRAM|_NEW_ARRAY)) {
       exec->array.recalculate_inputs = GL_TRUE;
-
-      /* If we ended up here because a VAO was deleted, the _DrawArrays
-       * pointer which pointed to the VAO might be invalid now, so set it
-       * to NULL.  This prevents crashes in driver functions like Clear
-       * where driver state validation might occur, but the vbo module is
-       * still in an invalid state.
-       *
-       * Drivers should skip vertex array state validation if _DrawArrays
-       * is NULL.  It also has no effect on performance, because attrib
-       * bindings will be recalculated anyway.
-       */
-      if (vbo->last_draw_method == DRAW_ARRAYS) {
-         ctx->Array._DrawArrays = NULL;
-         vbo->last_draw_method = DRAW_NONE;
-      }
    }
 
    if (new_state & _NEW_EVAL)