Fix review comments

Author: bjorn3

src/shims/foreign_items.rs

@@ -139,6 +139,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             Entry::Occupied(e) => e.into_mut(),
             Entry::Vacant(e) => {
                 // Find it if it was not cached.
+                // The is true in case of a weak definition.
                 let mut instance_and_crate: Option<(ty::Instance<'_>, CrateNum, bool)> = None;
                 helpers::iter_exported_symbols(tcx, |cnum, def_id| {
                     let attrs = tcx.codegen_fn_attrs(def_id);
@@ -161,6 +162,8 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                         if let Some((original_instance, original_cnum, original_is_weak)) =
                             instance_and_crate
                         {
+                            // There is more than one definition with this name. What we do now
+                            // depends on whether one or both definitions are weak.
                             match (is_weak, original_is_weak) {
                                 (false, true) => {
                                     // Original definition is a weak definition. Override it.
@@ -174,7 +177,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                                 (true, true) | (false, false) => {
                                     // Either both definitions are non-weak or both are weak. In
                                     // either case return an error. For weak definitions we error
-                                    // because it is undefined which definition would have been
+                                    // because it is unspecified which definition would have been
                                     // picked by the linker.
 
                                     // Make sure we are consistent wrt what is 'first' and 'second'.