[Mesa-dev] [PATCH 1/2] util: Fix foreach_list_typed_safe when exec_node is not at offset 0.

[Ian Romanick]

On 03/09/2015 06:36 PM, Kenneth Graunke wrote:
> From: Jason Ekstrand <jason.ekstrand at intel.com>
> 
> __next and __prev are pointers to the structure containing the exec_node
> link, not the embedded exec_node.  NULL checks would fail unless the
> embedded exec_node happened to be at offset 0 in the parent struct.

Wait... what?  That is 100% wrong.  They are pointers to the exec_node,
or every assumption of the list structure (like checking for the end of
the list) breaks.

> Signed-off-by: Jason Ekstrand <jason.ekstrand at intel.com>
> Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
> ---
>  src/glsl/list.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/src/glsl/list.h b/src/glsl/list.h
> index ddb98f7..680e963 100644
> --- a/src/glsl/list.h
> +++ b/src/glsl/list.h
> @@ -684,7 +684,7 @@ inline void exec_node::insert_before(exec_list *before)
>             exec_node_data(__type, (__list)->head, __field),                \
>                 * __next =                                                  \
>             exec_node_data(__type, (__node)->__field.next, __field);        \
> -        __next != NULL;                                                    \
> +        &__next->__field != NULL;                                          \
>          __node = __next, __next =                                          \
>             exec_node_data(__type, (__next)->__field.next, __field))
>  
> @@ -693,7 +693,7 @@ inline void exec_node::insert_before(exec_list *before)
>             exec_node_data(__type, (__list)->tail_pred, __field),           \
>                 * __prev =                                                  \
>             exec_node_data(__type, (__node)->__field.prev, __field);        \
> -        __prev != NULL;                                                    \
> +        &__prev->__field != NULL;                                          \
>          __node = __prev, __prev =                                          \
>             exec_node_data(__type, (__prev)->__field.prev, __field))
>  
>