Document link_section arbitrary bytes

Author: fmckeogh

src/librustc_typeck/check/mod.rs

@@ -1447,6 +1447,9 @@ fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: DefId, span: Span)
     // other executable formats. Namely we can only embed a list of bytes,
     // nothing with pointers to anything else or relocations. If any relocation
     // show up, reject them here.
+    // #[link_section] may contain arbitrary, or even undefined bytes, but it is
+    // the consumer's responsibility to ensure all bytes that have been read
+    // have defined values.
     let instance = ty::Instance::mono(tcx, id);
     let cid = GlobalId {
         instance,