[Mesa-dev] [PATCH 08/13] mesa: In emit_texenv() type mismatch was forced with typecast

[Matt Turner]

On Wed, Mar 12, 2014 at 2:11 PM, Juha-Pekka Heikkila
<juhapekka.heikkila at gmail.com> wrote:
> Type mismatch caused random memory to be copied when casted
> memory area was smaller than expected type.
>
> Signed-off-by: Juha-Pekka Heikkila <juhapekka.heikkila at gmail.com>
> ---
>  src/mesa/main/ff_fragment_shader.cpp | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/src/mesa/main/ff_fragment_shader.cpp b/src/mesa/main/ff_fragment_shader.cpp
> index cad67aa..3e00424 100644
> --- a/src/mesa/main/ff_fragment_shader.cpp
> +++ b/src/mesa/main/ff_fragment_shader.cpp
> @@ -888,14 +888,15 @@ emit_texenv(texenv_fragment_program *p, GLuint unit)
>          shift = new(p->mem_ctx) ir_constant((float)(1 << rgb_shift));
>        }
>        else {
> -        float const_data[4] = {
> -           float(1 << rgb_shift),
> -           float(1 << rgb_shift),
> -           float(1 << rgb_shift),
> -           float(1 << alpha_shift)
> -        };
> -        shift = new(p->mem_ctx) ir_constant(glsl_type::vec4_type,
> -                                            (ir_constant_data *)const_data);
> +         ir_constant_data const_data = { .f = {
> +                                             float(1 << rgb_shift),
> +                                             float(1 << rgb_shift),
> +                                             float(1 << rgb_shift),
> +                                             float(1 << alpha_shift)
> +                                             } };

Huh. I'm confused. I thought C++ didn't allow designated initializers.

gcc accepts it here, and only warns with -pedantic:

warning: ISO C++ does not allow C99 designated initializers [-Wpedantic]

Maybe it's just that MSVC doesn't support them? Google is telling me
that the only way to initialize a union in C++ is by initializing its
first field.

In the case that we can actually use designated initializers, Let's
indent this like so:

         ir_constant_data const_data = {
            .f = {
               float(1 << rgb_shift),
               float(1 << rgb_shift),
               float(1 << rgb_shift),
               float(1 << alpha_shift)
            }
         };

(and hope gmail doesn't mess that up.)