[LWG motions 2--5] Consolidates P2867R2, P2869R4, P2872R3, and P2875R4

source/compatibility.tex

@@ -155,6 +155,23 @@
                                                                         // OK in \CppXXVI{}
 \end{codeblock}
 
+\nodiffref
+\change
+Removal of atomic access API for \tcode{shared_ptr} objects.
+\rationale
+The old behavior was brittle. \tcode{shared_ptr} objects using the old API were
+not protected by the type system, and certain interactions with code not using
+this API would, in some cases, silently produce undefined behavior. A complete
+type-safe replacement is provided in the form of \tcode{atomic<shared_ptr<T>>}.
+\effect
+Deletion of an old feature where a superior replacement exists within the
+standard.
+\difficulty
+Violations will be diagnosed by the \Cpp{} translator, as there are no
+remaining overloads that would match such calls. Violations are addressed by
+replacing affected \tcode{shared_ptr<T>} objects with
+\tcode{atomic<shared_ptr<T>>}.
+
 \nodiffref
 \change
 Remove the \tcode{basic_string::reserve()} overload with no parameters.
@@ -190,6 +207,36 @@
 \item \tcode{little_endian}.
 \end{itemize}
 
+\nodiffref
+\change
+Remove header \libnoheader{strstream} and all its contents.
+\rationale
+The header has been deprecated since the original \Cpp{} standard; the
+\libheader{spanstream} header provides an updated, safer facility.
+Ongoing support is at implementer's discretion,
+exercising freedoms granted by \ref{zombie.names}.
+\effect
+A valid \CppXXIII{} program \tcode{\#include}-ing the header or importing the
+header unit may become ill-formed. Code that uses any of the following classes
+by importing one of the standard library modules may become ill-formed:
+\begin{itemize}
+\item \tcode{istrstream}
+\item \tcode{ostrstream}
+\item \tcode{strstream}
+\item \tcode{strstreambuf}
+\end{itemize}
+
+\change
+Remove convenience interfaces \tcode{wstring_convert} and
+\tcode{wbuffer_convert}.
+\rationale
+These features were underspecified with no clear error reporting mechanism and
+were deprecated for the last three editions of this standard.  Ongoing support
+is at implementer's discretion, exercising freedoms granted by
+\ref{zombie.names}.
+\effect
+A valid \CppXXIII{} program using these interfaces may become ill-formed.
+
 \rSec1[diff.cpp20]{\Cpp{} and ISO \CppXX{}}
 
 \rSec2[diff.cpp20.general]{General}