[Mesa-dev] [PATCH] mesa: Add null pointer checks before dereferencing

[Kenneth Graunke]

On 06/27/2013 02:20 PM, Anuj Phogat wrote:
> Assertions are not sufficient to check for null pointers as they don't
> show up in release builds. So, add explicit null pointer checks in the
> code.
>
> Signed-off-by: Anuj Phogat <anuj.phogat at gmail.com>
> ---
>   src/mesa/program/prog_execute.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
>
> diff --git a/src/mesa/program/prog_execute.c b/src/mesa/program/prog_execute.c
> index b902006..1bcbf6b 100644
> --- a/src/mesa/program/prog_execute.c
> +++ b/src/mesa/program/prog_execute.c
> @@ -200,6 +200,8 @@ fetch_vector4(const struct prog_src_register *source,
>   {
>      const GLfloat *src = get_src_register_pointer(source, machine);
>      ASSERT(src);
> +   if (src == NULL)
> +      return;
>
>      if (source->Swizzle == SWIZZLE_NOOP) {
>         /* no swizzling */
> @@ -303,6 +305,8 @@ fetch_vector1(const struct prog_src_register *source,
>   {
>      const GLfloat *src = get_src_register_pointer(source, machine);
>      ASSERT(src);
> +   if (src == NULL)
> +      return;
>
>      result[0] = src[GET_SWZ(source->Swizzle, 0)];
>
> @@ -320,6 +324,9 @@ fetch_vector1ui(const struct prog_src_register *source,
>                   const struct gl_program_machine *machine)
>   {
>      const GLuint *src = (GLuint *) get_src_register_pointer(source, machine);
> +   ASSERT(src);
> +   if (src == NULL)
> +      return 0;
>      return src[GET_SWZ(source->Swizzle, 0)];
>   }
>
> @@ -1439,8 +1446,11 @@ _mesa_execute_program(struct gl_context * ctx,
>            {
>               const struct prog_src_register *source = &inst->SrcReg[0];
>               const GLfloat *src = get_src_register_pointer(source, machine);
> +            ASSERT(src);
>               GLfloat result[4];
>               GLuint i;
> +            if (src == NULL)
> +               return GL_FALSE;
>               for (i = 0; i < 4; i++) {
>                  const GLuint swz = GET_SWZ(source->Swizzle, i);
>                  if (swz == SWIZZLE_ZERO)
>

I don't like this.  I would just put an abort() below the _mesa_problem 
in get_src_register_pointer.