remove 'format' from Error constructor calls

23 files changed, 159 insertions, 151 deletions

diff --git a/src/libstore/binary-cache-store.cc b/src/libstore/binary-cache-store.cc
index 3a2d84861..4b7385c6b 100644
--- a/src/libstore/binary-cache-store.cc
+++ b/src/libstore/binary-cache-store.cc
@@ -40,14 +40,14 @@ void BinaryCacheStore::init()
         upsertFile(cacheInfoFile, "StoreDir: " + storeDir + "\n", "text/x-nix-cache-info");
     } else {
         for (auto & line : tokenizeString<Strings>(*cacheInfo, "\n")) {
-            size_t colon = line.find(':');
-            if (colon == std::string::npos) continue;
+            size_t colon= line.find(':');
+            if (colon ==std::string::npos) continue;
             auto name = line.substr(0, colon);
             auto value = trim(line.substr(colon + 1, std::string::npos));
             if (name == "StoreDir") {
                 if (value != storeDir)
-                    throw Error(format("binary cache '%s' is for Nix stores with prefix '%s', not '%s'")
-                        % getUri() % value % storeDir);
+                    throw Error("binary cache '%s' is for Nix stores with prefix '%s', not '%s'",
+                        getUri(), value, storeDir);
             } else if (name == "WantMassQuery") {
                 wantMassQuery.setDefault(value == "1" ? "true" : "false");
             } else if (name == "Priority") {
diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 527d7ac42..2301adb16 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -453,7 +453,7 @@ static void commonChildInit(Pipe & logPipe)
        that e.g. ssh cannot open /dev/tty) and it doesn't receive
        terminal signals. */
     if (setsid() == -1)
-        throw SysError(format("creating a new session"));
+        throw SysError("creating a new session");
 
     /* Dup the write side of the logger pipe into stderr. */
     if (dup2(logPipe.writeSide.get(), STDERR_FILENO) == -1)
@@ -466,7 +466,7 @@ static void commonChildInit(Pipe & logPipe)
     /* Reroute stdin to /dev/null. */
     int fdDevNull = open(pathNullDevice.c_str(), O_RDWR);
     if (fdDevNull == -1)
-        throw SysError(format("cannot open '%1%'") % pathNullDevice);
+        throw SysError("cannot open '%1%'", pathNullDevice);
     if (dup2(fdDevNull, STDIN_FILENO) == -1)
         throw SysError("cannot dup null device into stdin");
     close(fdDevNull);
@@ -488,7 +488,7 @@ void handleDiffHook(
 
             auto diffRes = runProgram(diffHookOptions);
             if (!statusOk(diffRes.first))
-                throw ExecError(diffRes.first, fmt("diff-hook program '%1%' %2%", diffHook, statusToString(diffRes.first)));
+                throw ExecError(diffRes.first, "diff-hook program '%1%' %2%", diffHook, statusToString(diffRes.first));
 
             if (diffRes.second != "")
                 printError(chomp(diffRes.second));
@@ -534,8 +534,8 @@ UserLock::UserLock()
     /* Get the members of the build-users-group. */
     struct group * gr = getgrnam(settings.buildUsersGroup.get().c_str());
     if (!gr)
-        throw Error(format("the group '%1%' specified in 'build-users-group' does not exist")
-            % settings.buildUsersGroup);
+        throw Error("the group '%1%' specified in 'build-users-group' does not exist",
+            settings.buildUsersGroup);
     gid = gr->gr_gid;
 
     /* Copy the result of getgrnam. */
@@ -546,8 +546,8 @@ UserLock::UserLock()
     }
 
     if (users.empty())
-        throw Error(format("the build users group '%1%' has no members")
-            % settings.buildUsersGroup);
+        throw Error("the build users group '%1%' has no members",
+            settings.buildUsersGroup);
 
     /* Find a user account that isn't currently in use for another
        build. */
@@ -556,8 +556,8 @@ UserLock::UserLock()
 
         struct passwd * pw = getpwnam(i.c_str());
         if (!pw)
-            throw Error(format("the user '%1%' in the group '%2%' does not exist")
-                % i % settings.buildUsersGroup);
+            throw Error("the user '%1%' in the group '%2%' does not exist",
+                i, settings.buildUsersGroup);
 
         createDirs(settings.nixStateDir + "/userpool");
 
@@ -565,7 +565,7 @@ UserLock::UserLock()
 
         AutoCloseFD fd = open(fnUserLock.c_str(), O_RDWR | O_CREAT | O_CLOEXEC, 0600);
         if (!fd)
-            throw SysError(format("opening user lock '%1%'") % fnUserLock);
+            throw SysError("opening user lock '%1%'", fnUserLock);
 
         if (lockFile(fd.get(), ltWrite, false)) {
             fdUserLock = std::move(fd);
@@ -574,8 +574,8 @@ UserLock::UserLock()
 
             /* Sanity check... */
             if (uid == getuid() || uid == geteuid())
-                throw Error(format("the Nix user should not be a member of '%1%'")
-                    % settings.buildUsersGroup);
+                throw Error("the Nix user should not be a member of '%1%'",
+                    settings.buildUsersGroup);
 
 #if __linux__
             /* Get the list of supplementary groups of this build user.  This
@@ -585,7 +585,7 @@ UserLock::UserLock()
             int err = getgrouplist(pw->pw_name, pw->pw_gid,
                 supplementaryGIDs.data(), &ngroups);
             if (err == -1)
-                throw Error(format("failed to get list of supplementary groups for '%1%'") % pw->pw_name);
+                throw Error("failed to get list of supplementary groups for '%1%'", pw->pw_name);
 
             supplementaryGIDs.resize(ngroups);
 #endif
@@ -594,9 +594,9 @@ UserLock::UserLock()
         }
     }
 
-    throw Error(format("all build users are currently in use; "
-        "consider creating additional users and adding them to the '%1%' group")
-        % settings.buildUsersGroup);
+    throw Error("all build users are currently in use; "
+        "consider creating additional users and adding them to the '%1%' group",
+        settings.buildUsersGroup);
 }
 
 
@@ -1985,7 +1985,7 @@ void DerivationGoal::startBuilder()
         string s = get(drv->env, "exportReferencesGraph").value_or("");
         Strings ss = tokenizeString<Strings>(s);
         if (ss.size() % 2 != 0)
-            throw BuildError(format("odd number of tokens in 'exportReferencesGraph': '%1%'") % s);
+            throw BuildError("odd number of tokens in 'exportReferencesGraph': '%1%'", s);
         for (Strings::iterator i = ss.begin(); i != ss.end(); ) {
             string fileName = *i++;
             static std::regex regex("[A-Za-z_][A-Za-z0-9_.-]*");
@@ -2034,7 +2034,7 @@ void DerivationGoal::startBuilder()
                     worker.store.computeFSClosure(worker.store.parseStorePath(worker.store.toStorePath(i.second.source)), closure);
             } catch (InvalidPath & e) {
             } catch (Error & e) {
-                throw Error(format("while processing 'sandbox-paths': %s") % e.what());
+                throw Error("while processing 'sandbox-paths': %s", e.what());
             }
         for (auto & i : closure) {
             auto p = worker.store.printStorePath(i);
@@ -2081,10 +2081,10 @@ void DerivationGoal::startBuilder()
         printMsg(lvlChatty, format("setting up chroot environment in '%1%'") % chrootRootDir);
 
         if (mkdir(chrootRootDir.c_str(), 0750) == -1)
-            throw SysError(format("cannot create '%1%'") % chrootRootDir);
+            throw SysError("cannot create '%1%'", chrootRootDir);
 
         if (buildUser && chown(chrootRootDir.c_str(), 0, buildUser->getGID()) == -1)
-            throw SysError(format("cannot change ownership of '%1%'") % chrootRootDir);
+            throw SysError("cannot change ownership of '%1%'", chrootRootDir);
 
         /* Create a writable /tmp in the chroot.  Many builders need
            this.  (Of course they should really respect $TMPDIR
@@ -2128,7 +2128,7 @@ void DerivationGoal::startBuilder()
         chmod_(chrootStoreDir, 01775);
 
         if (buildUser && chown(chrootStoreDir.c_str(), 0, buildUser->getGID()) == -1)
-            throw SysError(format("cannot change ownership of '%1%'") % chrootStoreDir);
+            throw SysError("cannot change ownership of '%1%'", chrootStoreDir);
 
         for (auto & i : inputPaths) {
             auto p = worker.store.printStorePath(i);
@@ -2161,7 +2161,7 @@ void DerivationGoal::startBuilder()
     if (needsHashRewrite()) {
 
         if (pathExists(homeDir))
-            throw Error(format("directory '%1%' exists; please remove it") % homeDir);
+            throw Error("directory '%1%' exists; please remove it", homeDir);
 
         /* We're not doing a chroot build, but we have some valid
            output paths.  Since we can't just overwrite or delete
@@ -2206,8 +2206,7 @@ void DerivationGoal::startBuilder()
                 if (line == "extra-sandbox-paths" || line == "extra-chroot-dirs") {
                     state = stExtraChrootDirs;
                 } else {
-                    throw Error(format("unknown pre-build hook command '%1%'")
-                        % line);
+                    throw Error("unknown pre-build hook command '%1%'", line);
                 }
             } else if (state == stExtraChrootDirs) {
                 if (line == "") {
@@ -2967,7 +2966,7 @@ void DerivationGoal::chownToBuilder(const Path & path)
 {
     if (!buildUser) return;
     if (chown(path.c_str(), buildUser->getUID(), buildUser->getGID()) == -1)
-        throw SysError(format("cannot change ownership of '%1%'") % path);
+        throw SysError("cannot change ownership of '%1%'", path);
 }
 
 
@@ -3104,7 +3103,7 @@ void DerivationGoal::runChild()
             /* Bind-mount chroot directory to itself, to treat it as a
                different filesystem from /, as needed for pivot_root. */
             if (mount(chrootRootDir.c_str(), chrootRootDir.c_str(), 0, MS_BIND, 0) == -1)
-                throw SysError(format("unable to bind mount '%1%'") % chrootRootDir);
+                throw SysError("unable to bind mount '%1%'", chrootRootDir);
 
             /* Bind-mount the sandbox's Nix store onto itself so that
                we can mark it as a "shared" subtree, allowing bind
@@ -3238,16 +3237,16 @@ void DerivationGoal::runChild()
 
             /* Do the chroot(). */
             if (chdir(chrootRootDir.c_str()) == -1)
-                throw SysError(format("cannot change directory to '%1%'") % chrootRootDir);
+                throw SysError("cannot change directory to '%1%'", chrootRootDir);
 
             if (mkdir("real-root", 0) == -1)
                 throw SysError("cannot create real-root directory");
 
             if (pivot_root(".", "real-root") == -1)
-                throw SysError(format("cannot pivot old root directory onto '%1%'") % (chrootRootDir + "/real-root"));
+                throw SysError("cannot pivot old root directory onto '%1%'", (chrootRootDir + "/real-root"));
 
             if (chroot(".") == -1)
-                throw SysError(format("cannot change root directory to '%1%'") % chrootRootDir);
+                throw SysError("cannot change root directory to '%1%'", chrootRootDir);
 
             if (umount2("real-root", MNT_DETACH) == -1)
                 throw SysError("cannot unmount real root filesystem");
@@ -3268,7 +3267,7 @@ void DerivationGoal::runChild()
 #endif
 
         if (chdir(tmpDirInSandbox.c_str()) == -1)
-            throw SysError(format("changing into '%1%'") % tmpDir);
+            throw SysError("changing into '%1%'", tmpDir);
 
         /* Close all other file descriptors. */
         closeMostFDs({STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO});
@@ -3407,9 +3406,9 @@ void DerivationGoal::runChild()
                 sandboxProfile += "(allow file-read* file-write* process-exec\n";
                 for (auto & i : dirsInChroot) {
                     if (i.first != i.second.source)
-                        throw Error(format(
-                            "can't map '%1%' to '%2%': mismatched impure paths not supported on Darwin")
-                            % i.first % i.second.source);
+                        throw Error(
+                            "can't map '%1%' to '%2%': mismatched impure paths not supported on Darwin",
+                            i.first, i.second.source);
 
                     string path = i.first;
                     struct stat st;
@@ -3500,7 +3499,7 @@ void DerivationGoal::runChild()
                 else if (drv->builder == "builtin:unpack-channel")
                     builtinUnpackChannel(drv2);
                 else
-                    throw Error(format("unsupported builtin function '%1%'") % string(drv->builder, 8));
+                    throw Error("unsupported builtin function '%1%'", string(drv->builder, 8));
                 _exit(0);
             } catch (std::exception & e) {
                 writeFull(STDERR_FILENO, "error: " + string(e.what()) + "\n");
@@ -3510,7 +3509,7 @@ void DerivationGoal::runChild()
 
         execve(builder, stringsToCharPtrs(args).data(), stringsToCharPtrs(envStrs).data());
 
-        throw SysError(format("executing '%1%'") % drv->builder);
+        throw SysError("executing '%1%'", drv->builder);
 
     } catch (std::exception & e) {
         writeFull(STDERR_FILENO, "\1while setting up the build environment: " + string(e.what()) + "\n");
@@ -3595,7 +3594,7 @@ void DerivationGoal::registerOutputs()
                     replaceValidPath(path, actualPath);
                 else
                     if (buildMode != bmCheck && rename(actualPath.c_str(), worker.store.toRealPath(path).c_str()) == -1)
-                        throw SysError(format("moving build output '%1%' from the sandbox to the Nix store") % path);
+                        throw SysError("moving build output '%1%' from the sandbox to the Nix store", path);
             }
             if (buildMode != bmCheck) actualPath = worker.store.toRealPath(path);
         }
@@ -3616,13 +3615,13 @@ void DerivationGoal::registerOutputs()
            user. */
         if ((!S_ISLNK(st.st_mode) && (st.st_mode & (S_IWGRP | S_IWOTH))) ||
             (buildUser && st.st_uid != buildUser->getUID()))
-            throw BuildError(format("suspicious ownership or permission on '%1%'; rejecting this build output") % path);
+            throw BuildError("suspicious ownership or permission on '%1%'; rejecting this build output", path);
 #endif
 
         /* Apply hash rewriting if necessary. */
         bool rewritten = false;
         if (!outputRewrites.empty()) {
-            printError(format("warning: rewriting hashes in '%1%'; cross fingers") % path);
+            printError("warning: rewriting hashes in '%1%'; cross fingers", path);
 
             /* Canonicalise first.  This ensures that the path we're
                rewriting doesn't contain a hard link to /etc/shadow or
@@ -3654,7 +3653,8 @@ void DerivationGoal::registerOutputs()
                 /* The output path should be a regular file without execute permission. */
                 if (!S_ISREG(st.st_mode) || (st.st_mode & S_IXUSR) != 0)
                     throw BuildError(
-                        format("output path '%1%' should be a non-executable regular file") % path);
+                        "output path '%1%' should be a non-executable regular file",
+                        path);
             }
 
             /* Check the hash. In hash mode, move the path produced by
@@ -3715,7 +3715,7 @@ void DerivationGoal::registerOutputs()
                     Path dst = worker.store.toRealPath(path + checkSuffix);
                     deletePath(dst);
                     if (rename(actualPath.c_str(), dst.c_str()))
-                        throw SysError(format("renaming '%1%' to '%2%'") % actualPath % dst);
+                        throw SysError("renaming '%1%' to '%2%'", actualPath, dst);
 
                     handleDiffHook(
                         buildUser ? buildUser->getUID() : getuid(),
@@ -4014,7 +4014,7 @@ Path DerivationGoal::openLogFile()
         settings.compressLog ? ".bz2" : "");
 
     fdLogFile = open(logFileName.c_str(), O_CREAT | O_WRONLY | O_TRUNC | O_CLOEXEC, 0666);
-    if (!fdLogFile) throw SysError(format("creating log file '%1%'") % logFileName);
+    if (!fdLogFile) throw SysError("creating log file '%1%'", logFileName);
 
     logFileSink = std::make_shared<FdSink>(fdLogFile.get());
 
@@ -4522,7 +4522,6 @@ void SubstitutionGoal::handleEOF(int fd)
     if (fd == outPipe.readSide.get()) worker.wakeUp(shared_from_this());
 }
 
-
 //////////////////////////////////////////////////////////////////////
 
 
@@ -4739,9 +4738,9 @@ void Worker::run(const Goals & _topGoals)
         if (!children.empty() || !waitingForAWhile.empty())
             waitForInput();
         else {
-            if (awake.empty() && 0 == settings.maxBuildJobs) throw Error(
-                "unable to start any build; either increase '--max-jobs' "
-                "or enable remote builds");
+            if (awake.empty() && 0 == settings.maxBuildJobs) 
+                throw Error("unable to start any build; either increase '--max-jobs' "
+                            "or enable remote builds");
             assert(!awake.empty());
         }
     }
@@ -4754,7 +4753,6 @@ void Worker::run(const Goals & _topGoals)
     assert(!settings.keepGoing || children.empty());
 }
 
-
 void Worker::waitForInput()
 {
     printMsg(lvlVomit, "waiting for children");
@@ -4895,6 +4893,9 @@ void Worker::waitForInput()
 }
 
 
+
+
+
 unsigned int Worker::exitStatus()
 {
     /*
@@ -4994,7 +4995,6 @@ void LocalStore::buildPaths(const std::vector<StorePathWithOutputs> & drvPaths,
         throw Error(worker.exitStatus(), "build of %s failed", showPaths(failed));
 }
 
-
 BuildResult LocalStore::buildDerivation(const StorePath & drvPath, const BasicDerivation & drv,
     BuildMode buildMode)
 {
@@ -5055,4 +5055,8 @@ void LocalStore::repairPath(const StorePath & path)
 }
 
 
+
 }
+
+
+
diff --git a/src/libstore/builtins/buildenv.cc b/src/libstore/builtins/buildenv.cc
index 1b802d908..000769094 100644
--- a/src/libstore/builtins/buildenv.cc
+++ b/src/libstore/builtins/buildenv.cc
@@ -72,15 +72,15 @@ static void createLinks(State & state, const Path & srcDir, const Path & dstDir,
                     if (!S_ISDIR(lstat(target).st_mode))
                         throw Error("collision between '%1%' and non-directory '%2%'", srcFile, target);
                     if (unlink(dstFile.c_str()) == -1)
-                        throw SysError(format("unlinking '%1%'") % dstFile);
+                        throw SysError("unlinking '%1%'", dstFile);
                     if (mkdir(dstFile.c_str(), 0755) == -1)
-                        throw SysError(format("creating directory '%1%'"));
+                        throw SysError("creating directory '%1%'", dstFile);
                     createLinks(state, target, dstFile, state.priorities[dstFile]);
                     createLinks(state, srcFile, dstFile, priority);
                     continue;
                 }
             } else if (errno != ENOENT)
-                throw SysError(format("getting status of '%1%'") % dstFile);
+                throw SysError("getting status of '%1%'", dstFile);
         }
 
         else {
@@ -99,11 +99,11 @@ static void createLinks(State & state, const Path & srcDir, const Path & dstDir,
                     if (prevPriority < priority)
                         continue;
                     if (unlink(dstFile.c_str()) == -1)
-                        throw SysError(format("unlinking '%1%'") % dstFile);
+                        throw SysError("unlinking '%1%'", dstFile);
                 } else if (S_ISDIR(dstSt.st_mode))
                     throw Error("collision between non-directory '%1%' and directory '%2%'", srcFile, dstFile);
             } else if (errno != ENOENT)
-                throw SysError(format("getting status of '%1%'") % dstFile);
+                throw SysError("getting status of '%1%'", dstFile);
         }
 
         createSymlink(srcFile, dstFile);
diff --git a/src/libstore/builtins/fetchurl.cc b/src/libstore/builtins/fetchurl.cc
index f6ae5d2e6..223ed1fba 100644
--- a/src/libstore/builtins/fetchurl.cc
+++ b/src/libstore/builtins/fetchurl.cc
@@ -18,7 +18,7 @@ void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData)
 
     auto getAttr = [&](const string & name) {
         auto i = drv.env.find(name);
-        if (i == drv.env.end()) throw Error(format("attribute '%s' missing") % name);
+        if (i == drv.env.end()) throw Error("attribute '%s' missing", name);
         return i->second;
     };
 
@@ -54,7 +54,7 @@ void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData)
         auto executable = drv.env.find("executable");
         if (executable != drv.env.end() && executable->second == "1") {
             if (chmod(storePath.c_str(), 0755) == -1)
-                throw SysError(format("making '%1%' executable") % storePath);
+                throw SysError("making '%1%' executable", storePath);
         }
     };
 
diff --git a/src/libstore/daemon.cc b/src/libstore/daemon.cc
index d985f151b..f8b449e5e 100644
--- a/src/libstore/daemon.cc
+++ b/src/libstore/daemon.cc
@@ -747,7 +747,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
     }
 
     default:
-        throw Error(format("invalid operation %1%") % op);
+        throw Error("invalid operation %1%", op);
     }
 }
 
diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index 973ddc86a..f35b8cc43 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -87,7 +87,7 @@ static void expect(std::istream & str, const string & s)
     char s2[s.size()];
     str.read(s2, s.size());
     if (string(s2, s.size()) != s)
-        throw FormatError(format("expected string '%1%'") % s);
+        throw FormatError("expected string '%1%'", s);
 }
 
 
@@ -114,7 +114,7 @@ static Path parsePath(std::istream & str)
 {
     string s = parseString(str);
     if (s.size() == 0 || s[0] != '/')
-        throw FormatError(format("bad path '%1%' in derivation") % s);
+        throw FormatError("bad path '%1%' in derivation", s);
     return s;
 }
 
@@ -196,7 +196,7 @@ Derivation readDerivation(const Store & store, const Path & drvPath)
     try {
         return parseDerivation(store, readFile(drvPath));
     } catch (FormatError & e) {
-        throw Error(format("error parsing derivation '%1%': %2%") % drvPath % e.msg());
+        throw Error("error parsing derivation '%1%': %2%", drvPath, e.msg());
     }
 }
 
diff --git a/src/libstore/download.cc b/src/libstore/download.cc
index 5967d0425..7d0cb449b 100644
--- a/src/libstore/download.cc
+++ b/src/libstore/download.cc
@@ -113,7 +113,7 @@ struct CurlDownloader : public Downloader
             if (requestHeaders) curl_slist_free_all(requestHeaders);
             try {
                 if (!done)
-                    fail(DownloadError(Interrupted, format("download of '%s' was interrupted") % request.uri));
+                    fail(DownloadError(Interrupted, "download of '%s' was interrupted", request.uri));
             } catch (...) {
                 ignoreException();
             }
@@ -518,7 +518,7 @@ struct CurlDownloader : public Downloader
             int running;
             CURLMcode mc = curl_multi_perform(curlm, &running);
             if (mc != CURLM_OK)
-                throw nix::Error(format("unexpected error from curl_multi_perform(): %s") % curl_multi_strerror(mc));
+                throw nix::Error("unexpected error from curl_multi_perform(): %s", curl_multi_strerror(mc));
 
             /* Set the promises of any finished requests. */
             CURLMsg * msg;
@@ -548,7 +548,7 @@ struct CurlDownloader : public Downloader
             vomit("download thread waiting for %d ms", sleepTimeMs);
             mc = curl_multi_wait(curlm, extraFDs, 1, sleepTimeMs, &numfds);
             if (mc != CURLM_OK)
-                throw nix::Error(format("unexpected error from curl_multi_wait(): %s") % curl_multi_strerror(mc));
+                throw nix::Error("unexpected error from curl_multi_wait(): %s", curl_multi_strerror(mc));
 
             nextWakeup = std::chrono::steady_clock::time_point();
 
diff --git a/src/libstore/download.hh b/src/libstore/download.hh
index 5a131c704..8141928d2 100644
--- a/src/libstore/download.hh
+++ b/src/libstore/download.hh
@@ -128,8 +128,10 @@ class DownloadError : public Error
 {
 public:
     Downloader::Error error;
-    DownloadError(Downloader::Error error, const FormatOrString & fs)
-        : Error(fs), error(error)
+
+    template<typename... Args>
+    DownloadError(Downloader::Error error, const Args & ... args)
+        : Error(args...), error(error)
     { }
 };
 
diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index 0c3d89611..27bd3f3e9 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -38,7 +38,7 @@ AutoCloseFD LocalStore::openGCLock(LockType lockType)
 
     AutoCloseFD fdGCLock = open(fnGCLock.c_str(), O_RDWR | O_CREAT | O_CLOEXEC, 0600);
     if (!fdGCLock)
-        throw SysError(format("opening global GC lock '%1%'") % fnGCLock);
+        throw SysError("opening global GC lock '%1%'", fnGCLock);
 
     if (!lockFile(fdGCLock.get(), lockType, false)) {
         printError(format("waiting for the big garbage collector lock..."));
@@ -65,8 +65,8 @@ static void makeSymlink(const Path & link, const Path & target)
 
     /* Atomically replace the old one. */
     if (rename(tempLink.c_str(), link.c_str()) == -1)
-        throw SysError(format("cannot rename '%1%' to '%2%'")
-            % tempLink % link);
+        throw SysError("cannot rename '%1%' to '%2%'",
+            tempLink , link);
 }
 
 
@@ -91,15 +91,15 @@ Path LocalFSStore::addPermRoot(const StorePath & storePath,
     Path gcRoot(canonPath(_gcRoot));
 
     if (isInStore(gcRoot))
-        throw Error(format(
+        throw Error(
                 "creating a garbage collector root (%1%) in the Nix store is forbidden "
-                "(are you running nix-build inside the store?)") % gcRoot);
+                "(are you running nix-build inside the store?)", gcRoot);
 
     if (indirect) {
         /* Don't clobber the link if it already exists and doesn't
            point to the Nix store. */
         if (pathExists(gcRoot) && (!isLink(gcRoot) || !isInStore(readLink(gcRoot))))
-            throw Error(format("cannot create symlink '%1%'; already exists") % gcRoot);
+            throw Error("cannot create symlink '%1%'; already exists", gcRoot);
         makeSymlink(gcRoot, printStorePath(storePath));
         addIndirectRoot(gcRoot);
     }
@@ -109,10 +109,10 @@ Path LocalFSStore::addPermRoot(const StorePath & storePath,
             Path rootsDir = canonPath((format("%1%/%2%") % stateDir % gcRootsDir).str());
 
             if (string(gcRoot, 0, rootsDir.size() + 1) != rootsDir + "/")
-                throw Error(format(
+                throw Error(
                     "path '%1%' is not a valid garbage collector root; "
-                    "it's not in the directory '%2%'")
-                    % gcRoot % rootsDir);
+                    "it's not in the directory '%2%'",
+                    gcRoot, rootsDir);
         }
 
         if (baseNameOf(gcRoot) == std::string(storePath.to_string()))
@@ -170,7 +170,7 @@ void LocalStore::addTempRoot(const StorePath & path)
                way. */
             struct stat st;
             if (fstat(state->fdTempRoots.get(), &st) == -1)
-                throw SysError(format("statting '%1%'") % fnTempRoots);
+                throw SysError("statting '%1%'", fnTempRoots);
             if (st.st_size == 0) break;
 
             /* The garbage collector deleted this file before we could
@@ -211,7 +211,7 @@ void LocalStore::findTempRoots(FDs & fds, Roots & tempRoots, bool censor)
         if (!*fd) {
             /* It's okay if the file has disappeared. */
             if (errno == ENOENT) continue;
-            throw SysError(format("opening temporary roots file '%1%'") % path);
+            throw SysError("opening temporary roots file '%1%'", path);
         }
 
         /* This should work, but doesn't, for some reason. */
@@ -222,7 +222,7 @@ void LocalStore::findTempRoots(FDs & fds, Roots & tempRoots, bool censor)
            only succeed if the owning process has died.  In that case
            we don't care about its temporary roots. */
         if (lockFile(fd->get(), ltWrite, false)) {
-            printError(format("removing stale temporary roots file '%1%'") % path);
+            printError("removing stale temporary roots file '%1%'", path);
             unlink(path.c_str());
             writeFull(fd->get(), "d");
             continue;
@@ -398,7 +398,7 @@ void LocalStore::findRuntimeRoots(Roots & roots, bool censor)
                 if (!fdDir) {
                     if (errno == ENOENT || errno == EACCES)
                         continue;
-                    throw SysError(format("opening %1%") % fdStr);
+                    throw SysError("opening %1%", fdStr);
                 }
                 struct dirent * fd_ent;
                 while (errno = 0, fd_ent = readdir(fdDir.get())) {
@@ -408,7 +408,7 @@ void LocalStore::findRuntimeRoots(Roots & roots, bool censor)
                 if (errno) {
                     if (errno == ESRCH)
                         continue;
-                    throw SysError(format("iterating /proc/%1%/fd") % ent->d_name);
+                    throw SysError("iterating /proc/%1%/fd", ent->d_name);
                 }
                 fdDir.reset();
 
@@ -536,7 +536,7 @@ void LocalStore::deletePathRecursive(GCState & state, const Path & path)
     struct stat st;
     if (lstat(realPath.c_str(), &st)) {
         if (errno == ENOENT) return;
-        throw SysError(format("getting status of %1%") % realPath);
+        throw SysError("getting status of %1%", realPath);
     }
 
     printInfo(format("deleting '%1%'") % path);
@@ -554,10 +554,10 @@ void LocalStore::deletePathRecursive(GCState & state, const Path & path)
         // size.
         try {
             if (chmod(realPath.c_str(), st.st_mode | S_IWUSR) == -1)
-                throw SysError(format("making '%1%' writable") % realPath);
+                throw SysError("making '%1%' writable", realPath);
             Path tmp = trashDir + "/" + std::string(baseNameOf(path));
             if (rename(realPath.c_str(), tmp.c_str()))
-                throw SysError(format("unable to rename '%1%' to '%2%'") % realPath % tmp);
+                throw SysError("unable to rename '%1%' to '%2%'", realPath, tmp);
             state.bytesInvalidated += size;
         } catch (SysError & e) {
             if (e.errNo == ENOSPC) {
@@ -676,7 +676,7 @@ void LocalStore::tryToDelete(GCState & state, const Path & path)
 void LocalStore::removeUnusedLinks(const GCState & state)
 {
     AutoCloseDir dir(opendir(linksDir.c_str()));
-    if (!dir) throw SysError(format("opening directory '%1%'") % linksDir);
+    if (!dir) throw SysError("opening directory '%1%'", linksDir);
 
     long long actualSize = 0, unsharedSize = 0;
 
@@ -689,7 +689,7 @@ void LocalStore::removeUnusedLinks(const GCState & state)
 
         struct stat st;
         if (lstat(path.c_str(), &st) == -1)
-            throw SysError(format("statting '%1%'") % path);
+            throw SysError("statting '%1%'", path);
 
         if (st.st_nlink != 1) {
             actualSize += st.st_size;
@@ -700,14 +700,14 @@ void LocalStore::removeUnusedLinks(const GCState & state)
         printMsg(lvlTalkative, format("deleting unused link '%1%'") % path);
 
         if (unlink(path.c_str()) == -1)
-            throw SysError(format("deleting '%1%'") % path);
+            throw SysError("deleting '%1%'", path);
 
         state.results.bytesFreed += st.st_size;
     }
 
     struct stat st;
     if (stat(linksDir.c_str(), &st) == -1)
-        throw SysError(format("statting '%1%'") % linksDir);
+        throw SysError("statting '%1%'", linksDir);
     long long overhead = st.st_blocks * 512ULL;
 
     printInfo(format("note: currently hard linking saves %.2f MiB")
@@ -801,7 +801,7 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
         try {
 
             AutoCloseDir dir(opendir(realStoreDir.c_str()));
-            if (!dir) throw SysError(format("opening directory '%1%'") % realStoreDir);
+            if (!dir) throw SysError("opening directory '%1%'", realStoreDir);
 
             /* Read the store and immediately delete all paths that
                aren't valid.  When using --max-freed etc., deleting
diff --git a/src/libstore/local-binary-cache-store.cc b/src/libstore/local-binary-cache-store.cc
index 363be1443..48aca478c 100644
--- a/src/libstore/local-binary-cache-store.cc
+++ b/src/libstore/local-binary-cache-store.cc
@@ -74,7 +74,7 @@ static void atomicWrite(const Path & path, const std::string & s)
     AutoDelete del(tmp, false);
     writeFile(tmp, s);
     if (rename(tmp.c_str(), path.c_str()))
-        throw SysError(format("renaming '%1%' to '%2%'") % tmp % path);
+        throw SysError("renaming '%1%' to '%2%'", tmp, path);
     del.cancel();
 }
 
diff --git a/src/libstore/local-fs-store.cc b/src/libstore/local-fs-store.cc
index aa5abd835..2d564a0d7 100644
--- a/src/libstore/local-fs-store.cc
+++ b/src/libstore/local-fs-store.cc
@@ -22,7 +22,7 @@ struct LocalStoreAccessor : public FSAccessor
     {
         Path storePath = store->toStorePath(path);
         if (!store->isValidPath(store->parseStorePath(storePath)))
-            throw InvalidPath(format("path '%1%' is not a valid store path") % storePath);
+            throw InvalidPath("path '%1%' is not a valid store path", storePath);
         return store->getRealStoreDir() + std::string(path, store->storeDir.size());
     }
 
@@ -33,11 +33,11 @@ struct LocalStoreAccessor : public FSAccessor
         struct stat st;
         if (lstat(realPath.c_str(), &st)) {
             if (errno == ENOENT || errno == ENOTDIR) return {Type::tMissing, 0, false};
-            throw SysError(format("getting status of '%1%'") % path);
+            throw SysError("getting status of '%1%'", path);
         }
 
         if (!S_ISREG(st.st_mode) && !S_ISDIR(st.st_mode) && !S_ISLNK(st.st_mode))
-            throw Error(format("file '%1%' has unsupported type") % path);
+            throw Error("file '%1%' has unsupported type", path);
 
         return {
             S_ISREG(st.st_mode) ? Type::tRegular :
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index ae7513ad8..db5a3b53c 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -92,13 +92,13 @@ LocalStore::LocalStore(const Params & params)
         else {
             struct stat st;
             if (stat(realStoreDir.c_str(), &st))
-                throw SysError(format("getting attributes of path '%1%'") % realStoreDir);
+                throw SysError("getting attributes of path '%1%'", realStoreDir);
 
             if (st.st_uid != 0 || st.st_gid != gr->gr_gid || (st.st_mode & ~S_IFMT) != perm) {
                 if (chown(realStoreDir.c_str(), 0, gr->gr_gid) == -1)
-                    throw SysError(format("changing ownership of path '%1%'") % realStoreDir);
+                    throw SysError("changing ownership of path '%1%'", realStoreDir);
                 if (chmod(realStoreDir.c_str(), perm) == -1)
-                    throw SysError(format("changing permissions on path '%1%'") % realStoreDir);
+                    throw SysError("changing permissions on path '%1%'", realStoreDir);
             }
         }
     }
@@ -109,12 +109,12 @@ LocalStore::LocalStore(const Params & params)
         struct stat st;
         while (path != "/") {
             if (lstat(path.c_str(), &st))
-                throw SysError(format("getting status of '%1%'") % path);
+                throw SysError("getting status of '%1%'", path);
             if (S_ISLNK(st.st_mode))
-                throw Error(format(
+                throw Error(
                         "the path '%1%' is a symlink; "
-                        "this is not allowed for the Nix store and its parent directories")
-                    % path);
+                        "this is not allowed for the Nix store and its parent directories",
+                        path);
             path = dirOf(path);
         }
     }
@@ -155,8 +155,8 @@ LocalStore::LocalStore(const Params & params)
        upgrade.  */
     int curSchema = getSchema();
     if (curSchema > nixSchemaVersion)
-        throw Error(format("current Nix store schema is version %1%, but I only support %2%")
-            % curSchema % nixSchemaVersion);
+        throw Error("current Nix store schema is version %1%, but I only support %2%",
+             curSchema, nixSchemaVersion);
 
     else if (curSchema == 0) { /* new store */
         curSchema = nixSchemaVersion;
@@ -284,7 +284,7 @@ int LocalStore::getSchema()
     if (pathExists(schemaPath)) {
         string s = readFile(schemaPath);
         if (!string2Int(s, curSchema))
-            throw Error(format("'%1%' is corrupt") % schemaPath);
+            throw Error("'%1%' is corrupt", schemaPath);
     }
     return curSchema;
 }
@@ -293,7 +293,7 @@ int LocalStore::getSchema()
 void LocalStore::openDB(State & state, bool create)
 {
     if (access(dbDir.c_str(), R_OK | W_OK))
-        throw SysError(format("Nix database directory '%1%' is not writable") % dbDir);
+        throw SysError("Nix database directory '%1%' is not writable", dbDir);
 
     /* Open the Nix database. */
     string dbPath = dbDir + "/db.sqlite";
@@ -367,7 +367,7 @@ void LocalStore::makeStoreWritable()
             throw SysError("setting up a private mount namespace");
 
         if (mount(0, realStoreDir.c_str(), "none", MS_REMOUNT | MS_BIND, 0) == -1)
-            throw SysError(format("remounting %1% writable") % realStoreDir);
+            throw SysError("remounting %1% writable", realStoreDir);
     }
 #endif
 }
@@ -388,7 +388,7 @@ static void canonicaliseTimestampAndPermissions(const Path & path, const struct
                  | 0444
                  | (st.st_mode & S_IXUSR ? 0111 : 0);
             if (chmod(path.c_str(), mode) == -1)
-                throw SysError(format("changing mode of '%1%' to %2$o") % path % mode);
+                throw SysError("changing mode of '%1%' to %2$o", path, mode);
         }
 
     }
@@ -406,7 +406,7 @@ static void canonicaliseTimestampAndPermissions(const Path & path, const struct
 #else
         if (!S_ISLNK(st.st_mode) && utimes(path.c_str(), times) == -1)
 #endif
-            throw SysError(format("changing modification time of '%1%'") % path);
+            throw SysError("changing modification time of '%1%'", path);
     }
 }
 
@@ -415,7 +415,7 @@ void canonicaliseTimestampAndPermissions(const Path & path)
 {
     struct stat st;
     if (lstat(path.c_str(), &st))
-        throw SysError(format("getting attributes of path '%1%'") % path);
+        throw SysError("getting attributes of path '%1%'", path);
     canonicaliseTimestampAndPermissions(path, st);
 }
 
@@ -430,17 +430,17 @@ static void canonicalisePathMetaData_(const Path & path, uid_t fromUid, InodesSe
        setattrlist() to remove other attributes as well. */
     if (lchflags(path.c_str(), 0)) {
         if (errno != ENOTSUP)
-            throw SysError(format("clearing flags of path '%1%'") % path);
+            throw SysError("clearing flags of path '%1%'", path);
     }
 #endif
 
     struct stat st;
     if (lstat(path.c_str(), &st))
-        throw SysError(format("getting attributes of path '%1%'") % path);
+        throw SysError("getting attributes of path '%1%'", path);
 
     /* Really make sure that the path is of a supported type. */
     if (!(S_ISREG(st.st_mode) || S_ISDIR(st.st_mode) || S_ISLNK(st.st_mode)))
-        throw Error(format("file '%1%' has an unsupported type") % path);
+        throw Error("file '%1%' has an unsupported type", path);
 
 #if __linux__
     /* Remove extended attributes / ACLs. */
@@ -474,7 +474,7 @@ static void canonicalisePathMetaData_(const Path & path, uid_t fromUid, InodesSe
     if (fromUid != (uid_t) -1 && st.st_uid != fromUid) {
         assert(!S_ISDIR(st.st_mode));
         if (inodesSeen.find(Inode(st.st_dev, st.st_ino)) == inodesSeen.end())
-            throw BuildError(format("invalid ownership on file '%1%'") % path);
+            throw BuildError("invalid ownership on file '%1%'", path);
         mode_t mode = st.st_mode & ~S_IFMT;
         assert(S_ISLNK(st.st_mode) || (st.st_uid == geteuid() && (mode == 0444 || mode == 0555) && st.st_mtime == mtimeStore));
         return;
@@ -498,8 +498,8 @@ static void canonicalisePathMetaData_(const Path & path, uid_t fromUid, InodesSe
         if (!S_ISLNK(st.st_mode) &&
             chown(path.c_str(), geteuid(), getegid()) == -1)
 #endif
-            throw SysError(format("changing owner of '%1%' to %2%")
-                % path % geteuid());
+            throw SysError("changing owner of '%1%' to %2%",
+                  path, geteuid());
     }
 
     if (S_ISDIR(st.st_mode)) {
@@ -518,11 +518,11 @@ void canonicalisePathMetaData(const Path & path, uid_t fromUid, InodesSeen & ino
        be a symlink, since we can't change its ownership. */
     struct stat st;
     if (lstat(path.c_str(), &st))
-        throw SysError(format("getting attributes of path '%1%'") % path);
+        throw SysError("getting attributes of path '%1%'", path);
 
     if (st.st_uid != geteuid()) {
         assert(S_ISLNK(st.st_mode));
-        throw Error(format("wrong ownership of top-level store path '%1%'") % path);
+        throw Error("wrong ownership of top-level store path '%1%'", path);
     }
 }
 
@@ -1392,7 +1392,7 @@ static void makeMutable(const Path & path)
     AutoCloseFD fd = open(path.c_str(), O_RDONLY | O_NOFOLLOW | O_CLOEXEC);
     if (fd == -1) {
         if (errno == ELOOP) return; // it's a symlink
-        throw SysError(format("opening file '%1%'") % path);
+        throw SysError("opening file '%1%'", path);
     }
 
     unsigned int flags = 0, old;
diff --git a/src/libstore/nar-accessor.cc b/src/libstore/nar-accessor.cc
index b74480684..ca663d837 100644
--- a/src/libstore/nar-accessor.cc
+++ b/src/libstore/nar-accessor.cc
@@ -184,7 +184,7 @@ struct NarAccessor : public FSAccessor
         auto i = get(path);
 
         if (i.type != FSAccessor::Type::tDirectory)
-            throw Error(format("path '%1%' inside NAR file is not a directory") % path);
+            throw Error("path '%1%' inside NAR file is not a directory", path);
 
         StringSet res;
         for (auto & child : i.children)
@@ -197,7 +197,7 @@ struct NarAccessor : public FSAccessor
     {
         auto i = get(path);
         if (i.type != FSAccessor::Type::tRegular)
-            throw Error(format("path '%1%' inside NAR file is not a regular file") % path);
+            throw Error("path '%1%' inside NAR file is not a regular file", path);
 
         if (getNarBytes) return getNarBytes(i.start, i.size);
 
@@ -209,7 +209,7 @@ struct NarAccessor : public FSAccessor
     {
         auto i = get(path);
         if (i.type != FSAccessor::Type::tSymlink)
-            throw Error(format("path '%1%' inside NAR file is not a symlink") % path);
+            throw Error("path '%1%' inside NAR file is not a symlink", path);
         return i.target;
     }
 };
diff --git a/src/libstore/nar-info.cc b/src/libstore/nar-info.cc
index 1375094b5..fbdcd7786 100644
--- a/src/libstore/nar-info.cc
+++ b/src/libstore/nar-info.cc
@@ -7,7 +7,7 @@ NarInfo::NarInfo(const Store & store, const std::string & s, const std::string &
     : ValidPathInfo(StorePath::dummy.clone()) // FIXME: hack
 {
     auto corrupt = [&]() {
-        throw Error(format("NAR info file '%1%' is corrupt") % whence);
+        throw Error("NAR info file '%1%' is corrupt", whence);
     };
 
     auto parseHashField = [&](const string & s) {
diff --git a/src/libstore/optimise-store.cc b/src/libstore/optimise-store.cc
index 8ac382e9d..f9cf2bb6b 100644
--- a/src/libstore/optimise-store.cc
+++ b/src/libstore/optimise-store.cc
@@ -19,9 +19,9 @@ static void makeWritable(const Path & path)
 {
     struct stat st;
     if (lstat(path.c_str(), &st))
-        throw SysError(format("getting attributes of path '%1%'") % path);
+        throw SysError("getting attributes of path '%1%'", path);
     if (chmod(path.c_str(), st.st_mode | S_IWUSR) == -1)
-        throw SysError(format("changing writability of '%1%'") % path);
+        throw SysError("changing writability of '%1%'", path);
 }
 
 
@@ -47,7 +47,7 @@ LocalStore::InodeHash LocalStore::loadInodeHash()
     InodeHash inodeHash;
 
     AutoCloseDir dir(opendir(linksDir.c_str()));
-    if (!dir) throw SysError(format("opening directory '%1%'") % linksDir);
+    if (!dir) throw SysError("opening directory '%1%'", linksDir);
 
     struct dirent * dirent;
     while (errno = 0, dirent = readdir(dir.get())) { /* sic */
@@ -55,7 +55,7 @@ LocalStore::InodeHash LocalStore::loadInodeHash()
         // We don't care if we hit non-hash files, anything goes
         inodeHash.insert(dirent->d_ino);
     }
-    if (errno) throw SysError(format("reading directory '%1%'") % linksDir);
+    if (errno) throw SysError("reading directory '%1%'", linksDir);
 
     printMsg(lvlTalkative, format("loaded %1% hash inodes") % inodeHash.size());
 
@@ -68,7 +68,7 @@ Strings LocalStore::readDirectoryIgnoringInodes(const Path & path, const InodeHa
     Strings names;
 
     AutoCloseDir dir(opendir(path.c_str()));
-    if (!dir) throw SysError(format("opening directory '%1%'") % path);
+    if (!dir) throw SysError("opening directory '%1%'", path);
 
     struct dirent * dirent;
     while (errno = 0, dirent = readdir(dir.get())) { /* sic */
@@ -83,7 +83,7 @@ Strings LocalStore::readDirectoryIgnoringInodes(const Path & path, const InodeHa
         if (name == "." || name == "..") continue;
         names.push_back(name);
     }
-    if (errno) throw SysError(format("reading directory '%1%'") % path);
+    if (errno) throw SysError("reading directory '%1%'", path);
 
     return names;
 }
@@ -96,7 +96,7 @@ void LocalStore::optimisePath_(Activity * act, OptimiseStats & stats,
 
     struct stat st;
     if (lstat(path.c_str(), &st))
-        throw SysError(format("getting attributes of path '%1%'") % path);
+        throw SysError("getting attributes of path '%1%'", path);
 
 #if __APPLE__
     /* HFS/macOS has some undocumented security feature disabling hardlinking for
@@ -130,7 +130,7 @@ void LocalStore::optimisePath_(Activity * act, OptimiseStats & stats,
        NixOS (example: $fontconfig/var/cache being modified).  Skip
        those files.  FIXME: check the modification time. */
     if (S_ISREG(st.st_mode) && (st.st_mode & S_IWUSR)) {
-        printError(format("skipping suspicious writable file '%1%'") % path);
+        printError("skipping suspicious writable file '%1%'", path);
         return;
     }
 
@@ -186,7 +186,7 @@ void LocalStore::optimisePath_(Activity * act, OptimiseStats & stats,
        current file with a hard link to that file. */
     struct stat stLink;
     if (lstat(linkPath.c_str(), &stLink))
-        throw SysError(format("getting attributes of path '%1%'") % linkPath);
+        throw SysError("getting attributes of path '%1%'", linkPath);
 
     if (st.st_ino == stLink.st_ino) {
         debug(format("'%1%' is already linked to '%2%'") % path % linkPath);
@@ -194,7 +194,7 @@ void LocalStore::optimisePath_(Activity * act, OptimiseStats & stats,
     }
 
     if (st.st_size != stLink.st_size) {
-        printError(format("removing corrupted link '%1%'") % linkPath);
+        printError("removing corrupted link '%1%'", linkPath);
         unlink(linkPath.c_str());
         goto retry;
     }
@@ -229,7 +229,7 @@ void LocalStore::optimisePath_(Activity * act, OptimiseStats & stats,
     /* Atomically replace the old file with the new hard link. */
     if (rename(tempLink.c_str(), path.c_str()) == -1) {
         if (unlink(tempLink.c_str()) == -1)
-            printError(format("unable to unlink '%1%'") % tempLink);
+            printError("unable to unlink '%1%'", tempLink);
         if (errno == EMLINK) {
             /* Some filesystems generate too many links on the rename,
                rather than on the original link.  (Probably it
@@ -238,7 +238,7 @@ void LocalStore::optimisePath_(Activity * act, OptimiseStats & stats,
             debug("'%s' has reached maximum number of links", linkPath);
             return;
         }
-        throw SysError(format("cannot rename '%1%' to '%2%'") % tempLink % path);
+        throw SysError("cannot rename '%1%' to '%2%'", tempLink, path);
     }
 
     stats.filesLinked++;
diff --git a/src/libstore/pathlocks.cc b/src/libstore/pathlocks.cc
index 2635e3940..52d430ffd 100644
--- a/src/libstore/pathlocks.cc
+++ b/src/libstore/pathlocks.cc
@@ -20,7 +20,7 @@ AutoCloseFD openLockFile(const Path & path, bool create)
 
     fd = open(path.c_str(), O_CLOEXEC | O_RDWR | (create ? O_CREAT : 0), 0600);
     if (!fd && (create || errno != ENOENT))
-        throw SysError(format("opening lock file '%1%'") % path);
+        throw SysError("opening lock file '%1%'", path);
 
     return fd;
 }
@@ -51,7 +51,7 @@ bool lockFile(int fd, LockType lockType, bool wait)
         while (flock(fd, type) != 0) {
             checkInterrupt();
             if (errno != EINTR)
-                throw SysError(format("acquiring/releasing lock"));
+                throw SysError("acquiring/releasing lock");
             else
                 return false;
         }
@@ -60,7 +60,7 @@ bool lockFile(int fd, LockType lockType, bool wait)
             checkInterrupt();
             if (errno == EWOULDBLOCK) return false;
             if (errno != EINTR)
-                throw SysError(format("acquiring/releasing lock"));
+                throw SysError("acquiring/releasing lock");
         }
     }
 
@@ -124,7 +124,7 @@ bool PathLocks::lockPaths(const PathSet & paths,
                hasn't been unlinked). */
             struct stat st;
             if (fstat(fd.get(), &st) == -1)
-                throw SysError(format("statting lock file '%1%'") % lockPath);
+                throw SysError("statting lock file '%1%'", lockPath);
             if (st.st_size != 0)
                 /* This lock file has been unlinked, so we're holding
                    a lock on a deleted file.  This means that other
diff --git a/src/libstore/profiles.cc b/src/libstore/profiles.cc
index 2bef51878..6cfe393a4 100644
--- a/src/libstore/profiles.cc
+++ b/src/libstore/profiles.cc
@@ -50,7 +50,7 @@ Generations findGenerations(Path profile, int & curGen)
             gen.number = n;
             struct stat st;
             if (lstat(gen.path.c_str(), &st) != 0)
-                throw SysError(format("statting '%1%'") % gen.path);
+                throw SysError("statting '%1%'", gen.path);
             gen.creationTime = st.st_mtime;
             gens.push_back(gen);
         }
@@ -117,7 +117,7 @@ Path createGeneration(ref<LocalFSStore> store, Path profile, Path outPath)
 static void removeFile(const Path & path)
 {
     if (remove(path.c_str()) == -1)
-        throw SysError(format("cannot unlink '%1%'") % path);
+        throw SysError("cannot unlink '%1%'", path);
 }
 
 
@@ -149,7 +149,7 @@ void deleteGenerations(const Path & profile, const std::set<unsigned int> & gens
     Generations gens = findGenerations(profile, curGen);
 
     if (gensToDelete.find(curGen) != gensToDelete.end())
-        throw Error(format("cannot delete current generation of profile %1%'") % profile);
+        throw Error("cannot delete current generation of profile %1%'", profile);
 
     for (auto & i : gens) {
         if (gensToDelete.find(i.number) == gensToDelete.end()) continue;
@@ -226,7 +226,7 @@ void deleteGenerationsOlderThan(const Path & profile, const string & timeSpec, b
     int days;
 
     if (!string2Int(strDays, days) || days < 1)
-        throw Error(format("invalid number of days specifier '%1%'") % timeSpec);
+        throw Error("invalid number of days specifier '%1%'", timeSpec);
 
     time_t oldTime = curTime - days * 24 * 3600;
 
diff --git a/src/libstore/references.cc b/src/libstore/references.cc
index 102e15921..a10d536a3 100644
--- a/src/libstore/references.cc
+++ b/src/libstore/references.cc
@@ -92,7 +92,7 @@ PathSet scanForReferences(const string & path,
         auto baseName = std::string(baseNameOf(i));
         string::size_type pos = baseName.find('-');
         if (pos == string::npos)
-            throw Error(format("bad reference '%1%'") % i);
+            throw Error("bad reference '%1%'", i);
         string s = string(baseName, 0, pos);
         assert(s.size() == refLength);
         assert(backMap.find(s) == backMap.end());
diff --git a/src/libstore/remote-fs-accessor.cc b/src/libstore/remote-fs-accessor.cc
index 5a2d103b9..9277a8e6b 100644
--- a/src/libstore/remote-fs-accessor.cc
+++ b/src/libstore/remote-fs-accessor.cc
@@ -51,7 +51,7 @@ std::pair<ref<FSAccessor>, Path> RemoteFSAccessor::fetch(const Path & path_)
     std::string restPath = std::string(path, storePath.size());
 
     if (!store->isValidPath(store->parseStorePath(storePath)))
-        throw InvalidPath(format("path '%1%' is not a valid store path") % storePath);
+        throw InvalidPath("path '%1%' is not a valid store path", storePath);
 
     auto i = nars.find(storePath);
     if (i != nars.end()) return {i->second, restPath};
diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
index 8c55da268..0f8126aee 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -116,11 +116,11 @@ ref<RemoteStore::Connection> UDSRemoteStore::openConnection()
     struct sockaddr_un addr;
     addr.sun_family = AF_UNIX;
     if (socketPath.size() + 1 >= sizeof(addr.sun_path))
-        throw Error(format("socket path '%1%' is too long") % socketPath);
+        throw Error("socket path '%1%' is too long", socketPath);
     strcpy(addr.sun_path, socketPath.c_str());
 
     if (::connect(conn->fd.get(), (struct sockaddr *) &addr, sizeof(addr)) == -1)
-        throw SysError(format("cannot connect to daemon at '%1%'") % socketPath);
+        throw SysError("cannot connect to daemon at '%1%'", socketPath);
 
     conn->from.fd = conn->fd.get();
     conn->to.fd = conn->fd.get();
diff --git a/src/libstore/s3-binary-cache-store.cc b/src/libstore/s3-binary-cache-store.cc
index f2e4b63e0..0326821f6 100644
--- a/src/libstore/s3-binary-cache-store.cc
+++ b/src/libstore/s3-binary-cache-store.cc
@@ -32,8 +32,10 @@ namespace nix {
 struct S3Error : public Error
 {
     Aws::S3::S3Errors err;
-    S3Error(Aws::S3::S3Errors err, const FormatOrString & fs)
-        : Error(fs), err(err) { };
+
+    template<typename... Args>
+    S3Error(Aws::S3::S3Errors err, const Args & ... args)
+        : Error(args...), err(err) { };
 };
 
 /* Helper: given an Outcome<R, E>, return R in case of success, or
@@ -249,7 +251,7 @@ struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore
                 // If bucket listing is disabled, 404s turn into 403s
                 || error.GetErrorType() == Aws::S3::S3Errors::ACCESS_DENIED)
                 return false;
-            throw Error(format("AWS error fetching '%s': %s") % path % error.GetMessage());
+            throw Error("AWS error fetching '%s': %s", path, error.GetMessage());
         }
 
         return true;
diff --git a/src/libstore/sqlite.cc b/src/libstore/sqlite.cc
index eb1daafc5..3407e5826 100644
--- a/src/libstore/sqlite.cc
+++ b/src/libstore/sqlite.cc
@@ -29,7 +29,7 @@ SQLite::SQLite(const Path & path, bool create)
 {
     if (sqlite3_open_v2(path.c_str(), &db,
             SQLITE_OPEN_READWRITE | (create ? SQLITE_OPEN_CREATE : 0), 0) != SQLITE_OK)
-        throw Error(format("cannot open SQLite database '%s'") % path);
+        throw Error("cannot open SQLite database '%s'", path);
 
     if (sqlite3_busy_timeout(db, 60 * 60 * 1000) != SQLITE_OK)
         throwSQLiteError(db, "setting timeout");
diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index b9e894a9a..a04d5013e 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -22,7 +22,7 @@ bool Store::isInStore(const Path & path) const
 Path Store::toStorePath(const Path & path) const
 {
     if (!isInStore(path))
-        throw Error(format("path '%1%' is not in the Nix store") % path);
+        throw Error("path '%1%' is not in the Nix store", path);
     Path::size_type slash = path.find('/', storeDir.size() + 1);
     if (slash == Path::npos)
         return path;
@@ -40,7 +40,7 @@ Path Store::followLinksToStore(std::string_view _path) const
         path = absPath(target, dirOf(path));
     }
     if (!isInStore(path))
-        throw Error(format("path '%1%' is not in the Nix store") % path);
+        throw Error("path '%1%' is not in the Nix store", path);
     return path;
 }