Merge pull request #14156 from NixOS/fix-ub

treewide: Squash some user-after-free bugs

Author: Ericson2314

src/libexpr/eval-profiler.cc

@@ -324,7 +324,7 @@ void SampleStack::saveProfile()
             std::visit([&](auto && info) { info.symbolize(state, os, posCache); }, pos);
         }
         os << " " << count;
-        writeLine(profileFd.get(), std::move(os).str());
+        writeLine(profileFd.get(), os.str());
         /* Clear ostringstream. */
         os.str("");
         os.clear();

src/libstore/build/derivation-goal.cc

@@ -272,9 +272,10 @@ Goal::Co DerivationGoal::repairClosure()
                 bmRepair));
     }
 
+    bool haveWaitees = !waitees.empty();
     co_await await(std::move(waitees));
 
-    if (!waitees.empty()) {
+    if (haveWaitees) {
         trace("closure repaired");
         if (nrFailed > 0)
             throw Error(