platform.h: Define OSL_DEPRECATED_EXTERNAL

src/doc/Doxyfile

@@ -2167,12 +2167,14 @@ PREDEFINED             = DOXYGEN_SHOULD_SKIP_THIS \
                          OSL_CONSTEXPR14=constexpr \
                          OSL_CONSTEXPR17=constexpr \
                          OSL_CONSTEXPR20=constexpr \
+                         OSL_CONSTEXPR23=constexpr \
                          OSL_INLINE_CONSTEXPR="inline constexpr" \
                          OSL_PURE_FUNC= \
                          OSL_CONST_FUNC= \
                          OSL_MAYBE_UNUSED= \
                          OSL_NODISCARD=[[nodiscard]] \
                          OSL_DEPRECATED:=[[deprecated]] \
+                         OSL_DEPRECATED_EXTERNAL:=[[deprecated]] \
                          OSL_FORMAT_DEPRECATED:= \
                          OSL_ERRORHANDLER_PRINTF_DEPRECATED:= \
                          OSL_FORCEINLINE=inline \

src/include/OSL/platform.h

@@ -427,6 +427,15 @@
 // [[deprecated(msg)]] instead.
 #define OSL_DEPRECATED(msg) [[deprecated(msg)]]
 
+// OSL_DEPRECATED_EXTERNAL marks things deprecated for downstream apps, but
+// still is allowed for internal use. Generally, this is used when we want to
+// deprecate for users but can't quite extract it internally yet.
+#ifndef OSL_INTERNAL
+#  define OSL_DEPRECATED_EXTERNAL(msg) [[deprecated(msg)]]
+#else
+#  define OSL_DEPRECATED_EXTERNAL(msg)
+#endif
+
 
 // OSL_FALLTHROUGH at the end of a `case` label's statements documents that
 // the switch statement case is intentionally falling through to the code for