[Mesa-dev] [PATCH] i965: Make vec4_visitor's destructor virtual

[Francisco Jerez]

Iago Toral Quiroga <itoral at igalia.com> writes:

> We need a virtual destructor when at least one of the class' methods is virtual.
> Failure to do so leads to undefined behavior when destructing derived classes.
> Fixes the following warning:
>
> brw_vec4_gs_visitor.cpp: In function 'const unsigned int* brw::brw_gs_emit(brw_context*, gl_shader_program*, brw_gs_compile*, void*, unsigned int*)':
> brw_vec4_gs_visitor.cpp:703:11: warning: deleting object of polymorphic class type 'brw::vec4_gs_visitor' which has non-virtual destructor might cause undefined behaviour [-Wdelete-non-virtual-dtor]
>     delete gs;

I don't think this was leading to an actual bug because AFAICT
gen6_gs_visitor is the only subclass of vec4_visitor destroyed through a
pointer of a base class (vec4_gs_visitor *), and its destructor is
basically the same as its parent's.  Anyway it seems sensible to change
this so it doesn't bite us in the future.  If you clarify that in the
commit message this patch is:

Reviewed-by: Francisco Jerez <currojerez at riseup.net>

> ---
>  src/mesa/drivers/dri/i965/brw_vec4.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_vec4.h b/src/mesa/drivers/dri/i965/brw_vec4.h
> index d1fa095..5e3500c 100644
> --- a/src/mesa/drivers/dri/i965/brw_vec4.h
> +++ b/src/mesa/drivers/dri/i965/brw_vec4.h
> @@ -76,7 +76,7 @@ public:
>  		void *mem_ctx,
>                  bool no_spills,
>                  int shader_time_index);
> -   ~vec4_visitor();
> +   virtual ~vec4_visitor();
>  
>     dst_reg dst_null_f()
>     {
> -- 
> 1.9.1
>
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