Re: [PATCH] gdbsupport: add support for references to checked_static_cast

[Andrew Burgess via Gdb-patches <gdb-patches@sourceware.org>]

Simon Marchi via Gdb-patches <gdb-patches@sourceware.org> writes:

> Add a checked_static_cast overload that works with references.  A bad
> dynamic cast with references throws std::bad_cast, it would be possible
> to implement the new overload based on that, but it seemed simpler to
> just piggy back off the existing function.
>
> I found some potential uses of this new overload in amd-dbgapi-target.c,
> update them to illustrate the use of the new overload.  To build
> amd-dbgapi-target.c, on needs the amd-dbgapi library, which I don't
> expect many people to have.  But I have it, and it builds fine here.  I
> did test the new overload by making a purposely bad cast and it did
> catch it.

Looks great.  Thanks for expanding this feature.

Reviewed-By: Andrew Burgess <aburgess@redhat.com>

Thanks,
Andrew

>
> Change-Id: Id6b6a7db09fe3b4aa43cddb60575ff5f46761e96
> ---
>  gdb/amdgpu-tdep.c                    | 28 +++++++++++++++++++---------
>  gdbsupport/gdb-checked-static-cast.h | 16 ++++++++++++++++
>  2 files changed, 35 insertions(+), 9 deletions(-)
>
> diff --git a/gdb/amdgpu-tdep.c b/gdb/amdgpu-tdep.c
> index 1077fab5c65e..21a7a3ae1b79 100644
> --- a/gdb/amdgpu-tdep.c
> +++ b/gdb/amdgpu-tdep.c
> @@ -674,7 +674,8 @@ amd_dbgapi_register_type_to_gdb_type (const amd_dbgapi_register_type &type,
>      case amd_dbgapi_register_type::kind::INTEGER:
>        {
>  	const auto &integer_type
> -	  = static_cast<const amd_dbgapi_register_type_integer &> (type);
> +	  = gdb::checked_static_cast<const amd_dbgapi_register_type_integer &>
> +	      (type);
>  	switch (integer_type.bit_size ())
>  	  {
>  	  case 32:
> @@ -697,7 +698,8 @@ amd_dbgapi_register_type_to_gdb_type (const amd_dbgapi_register_type &type,
>      case amd_dbgapi_register_type::kind::VECTOR:
>        {
>  	const auto &vector_type
> -	  = static_cast<const amd_dbgapi_register_type_vector &> (type);
> +	  = gdb::checked_static_cast<const amd_dbgapi_register_type_vector &>
> +	      (type);
>  	struct type *element_type
>  	  = amd_dbgapi_register_type_to_gdb_type (vector_type.element_type (),
>  						  gdbarch);
> @@ -716,7 +718,8 @@ amd_dbgapi_register_type_to_gdb_type (const amd_dbgapi_register_type &type,
>      case amd_dbgapi_register_type::kind::FLAGS:
>        {
>  	const auto &flags_type
> -	  = static_cast<const amd_dbgapi_register_type_flags &> (type);
> +	  = gdb::checked_static_cast<const amd_dbgapi_register_type_flags &>
> +	      (type);
>  	struct type *gdb_type
>  	  = arch_flags_type (gdbarch, flags_type.name ().c_str (),
>  			     flags_type.bit_size ());
> @@ -747,7 +750,8 @@ amd_dbgapi_register_type_to_gdb_type (const amd_dbgapi_register_type &type,
>      case amd_dbgapi_register_type::kind::ENUM:
>        {
>  	const auto &enum_type
> -	  = static_cast<const amd_dbgapi_register_type_enum &> (type);
> +	  = gdb::checked_static_cast<const amd_dbgapi_register_type_enum &>
> +	      (type);
>  	struct type *gdb_type
>  	  = (type_allocator (gdbarch)
>  	     .new_type (TYPE_CODE_ENUM, enum_type.bit_size (),
> @@ -1310,7 +1314,8 @@ amdgpu_register_type_parse_test ()
>  
>      gdb_assert (type.kind () == amd_dbgapi_register_type::kind::FLAGS);
>  
> -    const auto &f = static_cast<const amd_dbgapi_register_type_flags &> (type);
> +    const auto &f
> +      = gdb::checked_static_cast<const amd_dbgapi_register_type_flags &> (type);
>      gdb_assert (f.size () == 23);
>  
>      /* Check the two "FP_ROUND" fields.  */
> @@ -1322,7 +1327,8 @@ amdgpu_register_type_parse_test ()
>  		      == amd_dbgapi_register_type::kind::ENUM);
>  
>  	  const auto &e
> -	    = static_cast<const amd_dbgapi_register_type_enum &> (*field.type);
> +	    = gdb::checked_static_cast<const amd_dbgapi_register_type_enum &>
> +	      (*field.type);
>  	  gdb_assert (e.size () == 4);
>  	  gdb_assert (e[0].name == "NEAREST_EVEN");
>  	  gdb_assert (e[0].value == 0);
> @@ -1338,7 +1344,8 @@ amdgpu_register_type_parse_test ()
>      gdb_assert (f[22].type->kind () == amd_dbgapi_register_type::kind::INTEGER);
>  
>      const auto &i
> -      = static_cast<const amd_dbgapi_register_type_integer &> (*f[22].type);
> +      = gdb::checked_static_cast<const amd_dbgapi_register_type_integer &>
> +	  (*f[22].type);
>      gdb_assert (i.bit_size () == 32);
>      gdb_assert (i.is_unsigned ());
>    }
> @@ -1352,13 +1359,16 @@ amdgpu_register_type_parse_test ()
>  
>      gdb_assert (type.kind () == amd_dbgapi_register_type::kind::VECTOR);
>  
> -    const auto &v = static_cast<const amd_dbgapi_register_type_vector &> (type);
> +    const auto &v
> +      = gdb::checked_static_cast<const amd_dbgapi_register_type_vector &>
> +	  (type);
>      gdb_assert (v.count () == 64);
>  
>      const auto &et = v.element_type ();
>      gdb_assert (et.kind () == amd_dbgapi_register_type::kind::INTEGER);
>  
> -    const auto &i = static_cast<const amd_dbgapi_register_type_integer &> (et);
> +    const auto &i
> +      = gdb::checked_static_cast<const amd_dbgapi_register_type_integer &> (et);
>      gdb_assert (i.bit_size () == 32);
>      gdb_assert (!i.is_unsigned ());
>    }
> diff --git a/gdbsupport/gdb-checked-static-cast.h b/gdbsupport/gdb-checked-static-cast.h
> index bc75244bddd0..7e5a69a6474d 100644
> --- a/gdbsupport/gdb-checked-static-cast.h
> +++ b/gdbsupport/gdb-checked-static-cast.h
> @@ -66,6 +66,22 @@ checked_static_cast (V *v)
>    return result;
>  }
>  
> +/* Same as the above, but to cast from a reference type to another.  */
> +
> +template<typename T, typename V>
> +T
> +checked_static_cast (V &v)
> +{
> +  static_assert (std::is_reference<T>::value, "target must be a reference type");
> +
> +  using T_no_R = typename std::remove_reference<T>::type;
> +  using T_P = typename std::add_pointer<T_no_R>::type;
> +
> +  using V_no_R = typename std::remove_reference<V>::type;
> +
> +  return *checked_static_cast<T_P, V_no_R> (&v);
> +}
> +
>  }
>  
>  #endif /* COMMON_GDB_CHECKED_DYNAMIC_CAST_H */
>
> base-commit: c96452ad168cf42ad42f0d57214dddb38d5fae88
> -- 
> 2.40.1