Make the fuchsia mojo/public repo the source of truth.

mojo/public/tools/bindings/generators/cpp_templates/validation_macros.tmpl

-{# TODO(vardhan): Fill out the remaining validation error strings. #}
-{%- macro validate_not_null_ptr(field_expr, field, object_name, err_string) %}
-if (!{{field_expr}}->offset) {
-  MOJO_INTERNAL_DEBUG_SET_ERROR_MSG({{err_string}})
-    << "null field '{{field.name}}' in '{{object_name}}'"; 
-  return mojo::internal::ValidationError::UNEXPECTED_NULL_POINTER;
-}
-{%- endmacro %}
-
-{%- macro validate_encoded_ptr(field_expr, err_string) %}
-if (!mojo::internal::ValidateEncodedPointer(&{{field_expr}}->offset)) {
-  MOJO_INTERNAL_DEBUG_SET_ERROR_MSG({{err_string}}) << "";
-  return mojo::internal::ValidationError::ILLEGAL_POINTER;
-}
-{%- endmacro %}
-
-{%- macro validate_array_or_string(field_expr, field, err_string) -%}
-const mojo::internal::ArrayValidateParams {{field.name}}_validate_params(
-    {{field.kind|get_array_validate_params_ctor_args|indent(4)}});
-auto validate_retval = {{field.kind|cpp_wrapper_type}}::Data_::Validate(
-        mojo::internal::DecodePointerRaw(&{{field_expr}}->offset),
-        bounds_checker, &{{field.name}}_validate_params,
-        {{err_string}});
-if (validate_retval != mojo::internal::ValidationError::NONE) {
-  return validate_retval;
-}
-{%- endmacro %}
-
-{%- macro validate_handle(field_expr, field, object_name, err_string) -%}
-  const mojo::Handle {{field.name}}_handle(object->data.f_{{field.name}});
-
-{%-   if not field.kind|is_nullable_kind %}
-  if ({{field.name}}_handle.value() == mojo::internal::kEncodedInvalidHandleValue) {
-    MOJO_INTERNAL_DEBUG_SET_ERROR_MSG({{err_string}})
-       << "invalid {{field.name}} field in {{object_name}}";
-    return mojo::internal::ValidationError::UNEXPECTED_INVALID_HANDLE;
-  }
-{%-   endif %}
-  if (!bounds_checker->ClaimHandle({{field.name}}_handle)) {
-    MOJO_INTERNAL_DEBUG_SET_ERROR_MSG({{err_string}}) << "";
-    return mojo::internal::ValidationError::ILLEGAL_HANDLE;
-  }
-{%- endmacro -%}
-
-{%- macro validate_union_field(field, union, err_string) %}
-{%-   set field_expr = "(reinterpret_cast<const "
-    ~ field.kind|cpp_union_field_type
-    ~ "*>(&object->data.f_"
-    ~ field.name
-    ~ "))" -%}
-{%-   if field.kind|is_object_kind -%}
-{%-     if not field.kind|is_nullable_kind -%}
-{{        validate_not_null_ptr(field_expr, field, union.name, err_string) }}
-{%-     endif %}
-{{      validate_encoded_ptr(field_expr, err_string) }}
-{%-   endif %}
-
-{%-   if field.kind|is_array_kind or field.kind|is_string_kind -%}
-{{      validate_array_or_string(field_expr, field, err_string) }}
-{%-   endif %}
-
-{%-   if field.kind|is_any_handle_kind -%}
-{{      validate_handle(field_expr, field, union.name, err_string) }}
-{%-   endif %}
-return mojo::internal::ValidationError::NONE;
-{%- endmacro %}