Don't copy in rethrow

src/libexpr/primops.cc

@@ -125,7 +125,7 @@ static void import(EvalState & state, const Pos & pos, Value & vPath, Value * vS
         });
     } catch (Error & e) {
         e.addTrace(pos, "while importing '%s'", path);
-        throw e;
+        throw;
     }
 
     Path realPath = state.checkSourcePath(state.toRealPath(path, context));
@@ -579,7 +579,7 @@ static Bindings::iterator getAttr(
             // Adding another trace for the function name to make it clear
             // which call received wrong arguments.
             e.addTrace(pos, hintfmt("while invoking '%s'", funcName));
-            throw e;
+            throw;
         }
     }
 
@@ -1717,7 +1717,7 @@ static void prim_fromJSON(EvalState & state, const Pos & pos, Value * * args, Va
         parseJSON(state, s, v);
     } catch (JSONParseError &e) {
         e.addTrace(pos, "while decoding a JSON string");
-        throw e;
+        throw;
     }
 }
 
@@ -2902,7 +2902,7 @@ static void prim_concatMap(EvalState & state, const Pos & pos, Value * * args, V
             state.forceList(lists[n], lists[n].determinePos(args[0]->determinePos(pos)));
         } catch (TypeError &e) {
             e.addTrace(pos, hintfmt("while invoking '%s'", "concatMap"));
-            throw e;
+            throw;
         }
         len += lists[n].listSize();
     }

src/libstore/build/derivation-goal.cc

@@ -1009,7 +1009,7 @@ HookReply DerivationGoal::tryBuildHook()
                     return readLine(worker.hook->fromHook.readSide.get());
                 } catch (Error & e) {
                     e.addTrace({}, "while reading the response from the build hook");
-                    throw e;
+                    throw;
                 }
             }();
             if (handleJSONLogMessage(s, worker.act, worker.hook->activities, true))
@@ -1055,7 +1055,7 @@ HookReply DerivationGoal::tryBuildHook()
         machineName = readLine(hook->fromHook.readSide.get());
     } catch (Error & e) {
         e.addTrace({}, "while reading the machine name from the build hook");
-        throw e;
+        throw;
     }
 
     /* Tell the hook all the inputs that have to be copied to the

src/libstore/build/local-derivation-goal.cc

@@ -943,7 +943,7 @@ void LocalDerivationGoal::startBuilder()
                     worker.store.printStorePath(drvPath),
                     statusToString(status),
                     concatStringsSep("|", msgs));
-                throw e;
+                throw;
             }
         }();
         if (string(msg, 0, 1) == "\2") break;
@@ -951,7 +951,7 @@ void LocalDerivationGoal::startBuilder()
             FdSource source(builderOut.readSide.get());
             auto ex = readError(source);
             ex.addTrace({}, "while setting up the build environment");
-            throw ex;
+            throw;
         }
         debug("sandbox setup: " + msg);
         msgs.push_back(std::move(msg));