gallium: add some checks for null surface pointers in state tracker

Fixes some segfaults in low memory situations.

src/mesa/state_tracker/st_atom_framebuffer.c

@@ -118,9 +118,10 @@ update_framebuffer_state( struct st_context *st )
             update_renderbuffer_surface(st, strb);
          }
 
-         assert(strb->surface);
+         if (strb->surface) {
-         framebuffer->cbufs[framebuffer->num_cbufs] = strb->surface;
+            framebuffer->cbufs[framebuffer->num_cbufs] = strb->surface;
-         framebuffer->num_cbufs++;
+            framebuffer->num_cbufs++;
+         }
       }
    }
 
@@ -132,7 +133,6 @@ update_framebuffer_state( struct st_context *st )
          update_renderbuffer_surface(st, strb);
       }
 
-      assert(strb->surface);
       framebuffer->zsbuf = strb->surface;
    }
    else {

src/mesa/state_tracker/st_cb_clear.c

@@ -406,13 +406,17 @@ check_clear_stencil_with_quad(GLcontext *ctx, struct gl_renderbuffer *rb)
 static void
 clear_color_buffer(GLcontext *ctx, struct gl_renderbuffer *rb)
 {
+   struct st_renderbuffer *strb = st_renderbuffer(rb);
+
+   if (!strb->surface)
+      return;
+
    if (check_clear_color_with_quad( ctx, rb )) {
       /* masking or scissoring */
       clear_with_quad(ctx, GL_TRUE, GL_FALSE, GL_FALSE);
    }
    else {
       /* clear whole buffer w/out masking */
-      struct st_renderbuffer *strb = st_renderbuffer(rb);
       uint clearValue;
       /* NOTE: we always pass the clear color as PIPE_FORMAT_A8R8G8B8_UNORM
        * at this time!
@@ -426,13 +430,16 @@ clear_color_buffer(GLcontext *ctx, struct gl_renderbuffer *rb)
 static void
 clear_depth_buffer(GLcontext *ctx, struct gl_renderbuffer *rb)
 {
+   struct st_renderbuffer *strb = st_renderbuffer(rb);
+
+   if (!strb->surface)
+      return;
+
    if (check_clear_depth_with_quad(ctx, rb)) {
       /* scissoring or we have a combined depth/stencil buffer */
       clear_with_quad(ctx, GL_FALSE, GL_TRUE, GL_FALSE);
    }
    else {
-      struct st_renderbuffer *strb = st_renderbuffer(rb);
-
       /* simple clear of whole buffer */
       uint clearValue = util_pack_z(strb->surface->format, ctx->Depth.Clear);
       ctx->st->pipe->clear(ctx->st->pipe, strb->surface, clearValue);
@@ -443,13 +450,16 @@ clear_depth_buffer(GLcontext *ctx, struct gl_renderbuffer *rb)
 static void
 clear_stencil_buffer(GLcontext *ctx, struct gl_renderbuffer *rb)
 {
+   struct st_renderbuffer *strb = st_renderbuffer(rb);
+
+   if (!strb->surface)
+      return;
+
    if (check_clear_stencil_with_quad(ctx, rb)) {
       /* masking or scissoring or combined depth/stencil buffer */
       clear_with_quad(ctx, GL_FALSE, GL_FALSE, GL_TRUE);
    }
    else {
-      struct st_renderbuffer *strb = st_renderbuffer(rb);
-
       /* simple clear of whole buffer */
       GLuint clearValue = ctx->Stencil.Clear;
 
@@ -469,14 +479,16 @@ clear_stencil_buffer(GLcontext *ctx, struct gl_renderbuffer *rb)
 static void
 clear_depth_stencil_buffer(GLcontext *ctx, struct gl_renderbuffer *rb)
 {
+   struct st_renderbuffer *strb = st_renderbuffer(rb);
+
+   if (!strb->surface)
+      return;
 
    if (check_clear_depth_stencil_with_quad(ctx, rb)) {
       /* masking or scissoring */
       clear_with_quad(ctx, GL_FALSE, GL_TRUE, GL_TRUE);
    }
    else {
-      struct st_renderbuffer *strb = st_renderbuffer(rb);
-
       /* clear whole buffer w/out masking */
       GLuint clearValue = util_pack_z(strb->surface->format, ctx->Depth.Clear);
 

src/mesa/state_tracker/st_framebuffer.c

@@ -289,7 +289,8 @@ st_notify_swapbuffers_complete(struct st_framebuffer *stfb)
       for (i = 0; i < BUFFER_COUNT; i++) {
 	 if (stfb->Base.Attachment[i].Renderbuffer) {
 	    strb = st_renderbuffer(stfb->Base.Attachment[i].Renderbuffer);
-	    strb->surface->status = PIPE_SURFACE_STATUS_UNDEFINED;
+            if (strb->surface)
+               strb->surface->status = PIPE_SURFACE_STATUS_UNDEFINED;
 	 }
       }
    }