================
@@ -6835,6 +6837,31 @@ the proper solution would be to create a different
function (possibly
an overload of ``baz()``) that accepts a safe container like ``bar()``,
and then use the attribute on the original ``baz()`` to help the users
update their code to use the new function.
+
+Attribute attached to fields:
+
+The attribute should only be attached to struct fields, if the fields can not
be
+updated to a safe type with bounds check, such as std::span. In other words,
the
+buffers prone to unsafe accesses should always be updated to use safe
containers/views
+and attaching the attribute must be last resort when such an update is
infeasible.
+
+The attribute can be placed on individual fields or a set of them as shown
below.
+.. code-block:: c++
+
+ struct A {
+ [[clang::unsafe_buffer_usage]]
+ int *ptr1;
+
+ [[clang::unsafe_buffer_usage]]
+ int *ptr2, buf[10];
+
+ [[clang::unsafe_buffer_usage]]
+ size_t sz;
+ };
+
+Here, every read/write to the fields ptr1, ptr2, buf and sz will trigger a
warning that the
+field has been explcitly marked as unsafe due to unsafe-buffer operations.
+
----------------
haoNoQ wrote:
I feel the need to add something constructive here, to give people a way to
eliminate the warning.
> "Together with adding the attribute, it is recommended to provide a safe way
> of accessing these structs. Under our assumption that the fields cannot be
> edited, or even made private, for compatibility reasons, one possible
> solution is to provide safe `span`-based accessor methods to these fields,
> then use the attribute to encourage users to use those methods, without
> breaking compatibility if they don't:
> ```
> struct A {
> [[clang::unsafe_buffer_usage]]
> int *ptr;
> [[clang::unsafe_buffer_usage]]
> size_t sz;
>
> std::span<int> getPtrAsSpan() {
> #pragma clang unsafe_buffer_usage begin
> return std::span{ptr, sz};
> #pragma clang unsafe_buffer_usage end
> }
>
> void setPtrFromSpan(std::span<int> sp) {
> #pragma clang unsafe_buffer_usage begin
> ptr = sp.data();
> sz = sp.size();
> #pragma clang unsafe_buffer_usage begin
> }
> }
> ```
> ".
https://github.com/llvm/llvm-project/pull/101585
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