Merge changes from topic "libutil-split" into main

* changes:
  util.hh: Delete remaining file and clean up headers
  util.hh: Move nativeSystem to local-derivation-goal.cc
  util.hh: Move stuff to types.hh
  util.cc: Delete remaining file
  util.{hh,cc}: Move ignoreException to error.{hh,cc}
  util.{hh,cc}: Split out namespaces.{hh,cc}
  util.{hh,cc}: Split out users.{hh,cc}
  util.{hh,cc}: Split out strings.{hh,cc}
  util.{hh,cc}: Split out unix-domain-socket.{hh,cc}
  util.{hh,cc}: Split out child.{hh,cc}
  util.{hh,cc}: Split out current-process.{hh,cc}
  util.{hh,cc}: Split out processes.{hh,cc}
  util.{hh,cc}: Split out file-descriptor.{hh,cc}
  util.{hh,cc}: Split out file-system.{hh,cc}
  util.{hh,cc}: Split out terminal.{hh,cc}
  util.{hh,cc}: Split out environment-variables.{hh,cc}

perl/lib/Nix/Store.xs

@@ -11,7 +11,6 @@
 #include "derivations.hh"
 #include "globals.hh"
 #include "store-api.hh"
-#include "util.hh"
 #include "crypto.hh"
 
 #include <sodium.h>

src/libcmd/common-eval-args.cc

@@ -2,7 +2,6 @@
 #include "common-eval-args.hh"
 #include "shared.hh"
 #include "filetransfer.hh"
-#include "util.hh"
 #include "eval.hh"
 #include "fetchers.hh"
 #include "registry.hh"

src/libcmd/editor-for.cc

@@ -1,5 +1,5 @@
-#include "util.hh"
 #include "editor-for.hh"
+#include "environment-variables.hh"
 #include "source-path.hh"
 
 namespace nix {

src/libcmd/installable-attr-path.cc

@@ -1,7 +1,6 @@
 #include "globals.hh"
 #include "installable-attr-path.hh"
 #include "outputs-spec.hh"
-#include "util.hh"
 #include "command.hh"
 #include "attr-path.hh"
 #include "common-eval-args.hh"

src/libcmd/installable-attr-path.hh

@@ -4,7 +4,6 @@
 #include "globals.hh"
 #include "installable-value.hh"
 #include "outputs-spec.hh"
-#include "util.hh"
 #include "command.hh"
 #include "attr-path.hh"
 #include "common-eval-args.hh"

src/libcmd/installable-flake.cc

@@ -2,7 +2,6 @@
 #include "installable-flake.hh"
 #include "installable-derived-path.hh"
 #include "outputs-spec.hh"
-#include "util.hh"
 #include "command.hh"
 #include "attr-path.hh"
 #include "common-eval-args.hh"

src/libcmd/installables.cc

@@ -3,26 +3,21 @@
 #include "installable-derived-path.hh"
 #include "installable-attr-path.hh"
 #include "installable-flake.hh"
+#include "logging.hh"
 #include "outputs-spec.hh"
-#include "util.hh"
 #include "command.hh"
 #include "attr-path.hh"
 #include "common-eval-args.hh"
 #include "derivations.hh"
-#include "eval-inline.hh"
 #include "eval.hh"
 #include "eval-settings.hh"
-#include "get-drvs.hh"
 #include "store-api.hh"
 #include "shared.hh"
 #include "flake/flake.hh"
 #include "eval-cache.hh"
-#include "url.hh"
 #include "registry.hh"
 #include "build-result.hh"
 
-#include <regex>
-#include <queue>
 
 #include <nlohmann/json.hpp>
 

src/libcmd/installables.hh

@@ -1,7 +1,6 @@
 #pragma once
 ///@file
 
-#include "util.hh"
 #include "path.hh"
 #include "outputs-spec.hh"
 #include "derived-path.hh"

src/libcmd/markdown.cc

@@ -1,6 +1,7 @@
 #include "markdown.hh"
-#include "util.hh"
+#include "error.hh"
 #include "finally.hh"
+#include "terminal.hh"
 
 #include <sys/queue.h>
 #include <lowdown.h>

src/libcmd/repl-interacter.cc

@@ -1,3 +1,7 @@
+#include "error.hh"
+#include "file-system.hh"
+#include "logging.hh"
+#include <csignal>
 #include <cstdio>
 #include <iostream>
 #include <string>
@@ -18,11 +22,8 @@ extern "C" {
 }
 #endif
 
-#include "signals.hh"
 #include "finally.hh"
 #include "repl-interacter.hh"
-#include "util.hh"
-#include "repl.hh"
 
 namespace nix {
 

src/libcmd/repl.cc

@@ -31,6 +31,7 @@
 #include "print.hh"
 #include "progress-bar.hh"
 #include "gc-small-vector.hh"
+#include "users.hh"
 
 #if HAVE_BOEHMGC
 #define GC_INCLUDE_NEW

src/libexpr/attr-path.cc

@@ -1,6 +1,5 @@
 #include "attr-path.hh"
 #include "eval-inline.hh"
-#include "util.hh"
 
 
 namespace nix {

src/libexpr/eval-cache.cc

@@ -1,8 +1,8 @@
 #include "eval-cache.hh"
 #include "sqlite.hh"
 #include "eval.hh"
-#include "eval-inline.hh"
 #include "store-api.hh"
+#include "users.hh"
 
 namespace nix::eval_cache {
 

src/libexpr/eval-settings.cc

@@ -1,6 +1,7 @@
+#include "file-system.hh"
 #include "globals.hh"
 #include "profiles.hh"
-#include "eval.hh"
+#include "users.hh"
 #include "eval-settings.hh"
 
 namespace nix {

src/libexpr/eval.cc

@@ -5,7 +5,6 @@
 #include "print-options.hh"
 #include "shared.hh"
 #include "types.hh"
-#include "util.hh"
 #include "store-api.hh"
 #include "derivations.hh"
 #include "downstream-placeholder.hh"

src/libexpr/flake/config.cc

@@ -1,5 +1,6 @@
 #include "flake.hh"
-#include "globals.hh"
+#include "logging.hh"
+#include "users.hh"
 #include "fetch-settings.hh"
 
 #include <nlohmann/json.hpp>

src/libexpr/flake/flake.cc

@@ -8,6 +8,7 @@
 #include "fetchers.hh"
 #include "finally.hh"
 #include "fetch-settings.hh"
+#include "terminal.hh"
 
 namespace nix {
 

src/libexpr/get-drvs.cc

@@ -1,5 +1,4 @@
 #include "get-drvs.hh"
-#include "util.hh"
 #include "eval-inline.hh"
 #include "derivations.hh"
 #include "store-api.hh"

src/libexpr/nixexpr.cc

@@ -2,7 +2,6 @@
 #include "derivations.hh"
 #include "eval.hh"
 #include "symbol-table.hh"
-#include "util.hh"
 #include "print.hh"
 #include "escape-string.hh"
 

src/libexpr/parser.y

@@ -19,7 +19,7 @@
 #include <variant>
 
 #include "finally.hh"
-#include "util.hh"
+#include "users.hh"
 
 #include "nixexpr.hh"
 #include "eval.hh"

src/libexpr/primops.cc

@@ -9,8 +9,8 @@
 #include "json-to-value.hh"
 #include "names.hh"
 #include "path-references.hh"
+#include "processes.hh"
 #include "store-api.hh"
-#include "util.hh"
 #include "value-to-json.hh"
 #include "value-to-xml.hh"
 #include "primops.hh"

src/libexpr/print-ambiguous.cc

@@ -1,6 +1,7 @@
 #include "print-ambiguous.hh"
+#include "attr-set.hh"
+#include "logging.hh"
 #include "print.hh"
-#include "eval.hh"
 #include "signals.hh"
 #include "escape-string.hh"
 

src/libexpr/print.cc

@@ -9,6 +9,7 @@
 #include "english.hh"
 #include "signals.hh"
 #include "eval.hh"
+#include "terminal.hh"
 
 namespace nix {
 

src/libexpr/search-path.cc

@@ -1,5 +1,4 @@
 #include "search-path.hh"
-#include "util.hh"
 
 namespace nix {
 

src/libexpr/value-to-json.cc

@@ -1,6 +1,5 @@
 #include "value-to-json.hh"
 #include "eval-inline.hh"
-#include "util.hh"
 #include "signals.hh"
 #include "store-api.hh"
 

src/libexpr/value-to-xml.cc

@@ -1,11 +1,7 @@
 #include "value-to-xml.hh"
 #include "xml-writer.hh"
-#include "eval-inline.hh"
-#include "util.hh"
 #include "signals.hh"
 
-#include <cstdlib>
-
 
 namespace nix {
 

src/libexpr/value/context.hh

@@ -1,7 +1,6 @@
 #pragma once
 ///@file
 
-#include "util.hh"
 #include "comparator.hh"
 #include "derived-path.hh"
 #include "variant-wrapper.hh"

src/libfetchers/cache.cc

@@ -2,6 +2,7 @@
 #include "sqlite.hh"
 #include "sync.hh"
 #include "store-api.hh"
+#include "users.hh"
 
 #include <nlohmann/json.hpp>
 

src/libfetchers/fetch-settings.hh

@@ -3,7 +3,6 @@
 
 #include "types.hh"
 #include "config.hh"
-#include "util.hh"
 
 #include <map>
 #include <limits>

src/libfetchers/fetch-to-store.hh

@@ -3,7 +3,6 @@
 
 #include "source-path.hh"
 #include "store-api.hh"
-#include "util.hh"
 #include "repair-flag.hh"
 #include "content-address.hh"
 

src/libfetchers/git.cc

@@ -1,11 +1,12 @@
 #include "fetchers.hh"
 #include "cache.hh"
 #include "globals.hh"
+#include "processes.hh"
 #include "tarfile.hh"
 #include "store-api.hh"
 #include "url-parts.hh"
 #include "pathlocks.hh"
-#include "util.hh"
+#include "users.hh"
 #include "git.hh"
 #include "logging.hh"
 #include "finally.hh"

src/libfetchers/mercurial.cc

@@ -1,9 +1,9 @@
 #include "fetchers.hh"
 #include "cache.hh"
-#include "globals.hh"
+#include "processes.hh"
-#include "tarfile.hh"
 #include "store-api.hh"
 #include "url-parts.hh"
+#include "users.hh"
 
 #include "fetch-settings.hh"
 

src/libfetchers/registry.cc

@@ -1,6 +1,6 @@
 #include "registry.hh"
 #include "fetchers.hh"
-#include "util.hh"
+#include "users.hh"
 #include "globals.hh"
 #include "store-api.hh"
 #include "local-fs-store.hh"

src/libmain/common-args.cc

@@ -2,6 +2,7 @@
 #include "args/root.hh"
 #include "globals.hh"
 #include "loggers.hh"
+#include "logging.hh"
 
 namespace nix {
 

src/libmain/loggers.cc

@@ -1,6 +1,6 @@
+#include "environment-variables.hh"
 #include "loggers.hh"
 #include "progress-bar.hh"
-#include "util.hh"
 
 namespace nix {
 

src/libmain/progress-bar.cc

@@ -1,8 +1,8 @@
 #include "progress-bar.hh"
-#include "util.hh"
 #include "sync.hh"
 #include "store-api.hh"
 #include "names.hh"
+#include "terminal.hh"
 
 #include <atomic>
 #include <map>

src/libmain/shared.cc

@@ -2,10 +2,10 @@
 #include "shared.hh"
 #include "store-api.hh"
 #include "gc-store.hh"
-#include "util.hh"
 #include "signals.hh"
 #include "loggers.hh"
 #include "progress-bar.hh"
+#include "current-process.hh"
 
 #include <algorithm>
 #include <cctype>

src/libmain/shared.hh

@@ -1,12 +1,12 @@
 #pragma once
 ///@file
 
-#include "util.hh"
 #include "args.hh"
 #include "args/root.hh"
 #include "common-args.hh"
 #include "path.hh"
 #include "derived-path.hh"
+#include "processes.hh"
 #include "exit.hh"
 
 #include <signal.h>

src/libstore/build/child.cc

@@ -0,0 +1,33 @@
+#include "current-process.hh"
+#include "logging.hh"
+
+namespace nix {
+
+void commonChildInit()
+{
+    logger = makeSimpleLogger();
+
+    const static std::string pathNullDevice = "/dev/null";
+    restoreProcessContext(false);
+
+    /* Put the child in a separate session (and thus a separate
+       process group) so that it has no controlling terminal (meaning
+       that e.g. ssh cannot open /dev/tty) and it doesn't receive
+       terminal signals. */
+    if (setsid() == -1)
+        throw SysError("creating a new session");
+
+    /* Dup stderr to stdout. */
+    if (dup2(STDERR_FILENO, STDOUT_FILENO) == -1)
+        throw SysError("cannot dup stderr into stdout");
+
+    /* Reroute stdin to /dev/null. */
+    int fdDevNull = open(pathNullDevice.c_str(), O_RDWR);
+    if (fdDevNull == -1)
+        throw SysError("cannot open '%1%'", pathNullDevice);
+    if (dup2(fdDevNull, STDIN_FILENO) == -1)
+        throw SysError("cannot dup null device into stdin");
+    close(fdDevNull);
+}
+
+}

src/libstore/build/child.hh

@@ -0,0 +1,11 @@
+#pragma once
+///@file
+
+namespace nix {
+
+/**
+ * Common initialisation performed in child processes.
+ */
+void commonChildInit();
+
+}

src/libstore/build/derivation-goal.cc

@@ -5,7 +5,6 @@
 #include "builtins/buildenv.hh"
 #include "references.hh"
 #include "finally.hh"
-#include "util.hh"
 #include "archive.hh"
 #include "compression.hh"
 #include "common-protocol.hh"

src/libstore/build/hook-instance.cc

@@ -1,3 +1,5 @@
+#include "child.hh"
+#include "file-system.hh"
 #include "globals.hh"
 #include "hook-instance.hh"
 

src/libstore/build/hook-instance.hh

@@ -2,6 +2,7 @@
 ///@file
 
 #include "logging.hh"
+#include "processes.hh"
 #include "serialise.hh"
 
 namespace nix {

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

@@ -6,7 +6,6 @@
 #include "builtins/buildenv.hh"
 #include "path-references.hh"
 #include "finally.hh"
-#include "util.hh"
 #include "archive.hh"
 #include "compression.hh"
 #include "daemon.hh"
@@ -15,6 +14,8 @@
 #include "cgroup.hh"
 #include "personality.hh"
 #include "namespaces.hh"
+#include "child.hh"
+#include "unix-domain-socket.hh"
 
 #include <regex>
 #include <queue>
@@ -63,6 +64,11 @@ extern "C" int sandbox_init_with_parameters(const char *profile, uint64_t flags,
 
 namespace nix {
 
+/**
+ * The system for which Nix is compiled.
+ */
+constexpr std::string_view nativeSystem = SYSTEM;
+
 void handleDiffHook(
     uid_t uid, uid_t gid,
     const Path & tryA, const Path & tryB,

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

@@ -3,6 +3,7 @@
 
 #include "derivation-goal.hh"
 #include "local-store.hh"
+#include "processes.hh"
 
 namespace nix {
 

src/libstore/common-protocol.cc

@@ -1,11 +1,8 @@
 #include "serialise.hh"
-#include "util.hh"
 #include "path-with-outputs.hh"
 #include "store-api.hh"
-#include "build-result.hh"
 #include "common-protocol.hh"
 #include "common-protocol-impl.hh"
-#include "archive.hh"
 #include "derivations.hh"
 
 #include <nlohmann/json.hpp>

src/libstore/crypto.cc

@@ -1,6 +1,7 @@
 #include "crypto.hh"
-#include "util.hh"
+#include "file-system.hh"
 #include "globals.hh"
+#include "strings.hh"
 
 #include <sodium.h>
 

src/libstore/crypto.hh

@@ -1,9 +1,9 @@
 #pragma once
 ///@file
 
-#include "types.hh"
 
 #include <map>
+#include <string>
 
 namespace nix {
 

src/libstore/derivations.cc

@@ -3,7 +3,6 @@
 #include "store-api.hh"
 #include "globals.hh"
 #include "types.hh"
-#include "util.hh"
 #include "split.hh"
 #include "common-protocol.hh"
 #include "common-protocol-impl.hh"

src/libstore/derived-path.hh

@@ -1,7 +1,7 @@
 #pragma once
 ///@file
 
-#include "util.hh"
+#include "config.hh"
 #include "path.hh"
 #include "outputs-spec.hh"
 #include "comparator.hh"

src/libstore/filetransfer.cc

@@ -1,5 +1,5 @@
 #include "filetransfer.hh"
-#include "util.hh"
+#include "namespaces.hh"
 #include "globals.hh"
 #include "store-api.hh"
 #include "s3.hh"
@@ -19,7 +19,6 @@
 #include <algorithm>
 #include <cmath>
 #include <cstring>
-#include <iostream>
 #include <queue>
 #include <random>
 #include <thread>

src/libstore/filetransfer.hh

@@ -1,8 +1,9 @@
 #pragma once
 ///@file
 
+#include "logging.hh"
+#include "serialise.hh"
 #include "types.hh"
-#include "hash.hh"
 #include "config.hh"
 
 #include <string>

src/libstore/gc.cc

@@ -1,16 +1,14 @@
-#include "derivations.hh"
 #include "globals.hh"
 #include "local-store.hh"
+#include "pathlocks.hh"
+#include "processes.hh"
 #include "signals.hh"
 #include "finally.hh"
+#include "unix-domain-socket.hh"
 
-#include <functional>
 #include <queue>
-#include <algorithm>
 #include <regex>
-#include <random>
 
-#include <climits>
 #include <errno.h>
 #include <fcntl.h>
 #include <poll.h>

src/libstore/globals.cc

@@ -1,12 +1,15 @@
+#include "environment-variables.hh"
 #include "globals.hh"
-#include "util.hh"
+#include "file-system.hh"
-#include "archive.hh"
+#include "logging.hh"
+#include "strings.hh"
+#include "users.hh"
 #include "args.hh"
 #include "abstract-setting-to-json.hh"
 #include "compute-levels.hh"
+#include "current-process.hh"
 
 #include <algorithm>
-#include <map>
 #include <mutex>
 #include <thread>
 #include <dlfcn.h>
@@ -25,6 +28,7 @@
 #include "config-impl.hh"
 
 #ifdef __APPLE__
+#include "processes.hh"
 #include <curl/curl.h>
 #include <sys/sysctl.h>
 #endif

src/libstore/globals.hh

@@ -1,9 +1,9 @@
 #pragma once
 ///@file
 
+#include "environment-variables.hh"
 #include "types.hh"
 #include "config.hh"
-#include "util.hh"
 
 #include <map>
 #include <limits>

src/libstore/local-store.hh

@@ -3,11 +3,9 @@
 
 #include "sqlite.hh"
 
-#include "pathlocks.hh"
 #include "store-api.hh"
 #include "indirect-root-store.hh"
 #include "sync.hh"
-#include "util.hh"
 
 #include <chrono>
 #include <future>

src/libstore/lock.cc

@@ -1,4 +1,6 @@
 #include "lock.hh"
+#include "logging.hh"
+#include "file-system.hh"
 #include "globals.hh"
 #include "pathlocks.hh"
 

src/libstore/machines.cc

@@ -1,7 +1,7 @@
 #include "machines.hh"
-#include "util.hh"
 #include "globals.hh"
 #include "store-api.hh"
+#include "strings.hh"
 
 #include <algorithm>
 

src/libstore/meson.build

@@ -79,6 +79,7 @@ libstore_sources = files(
   'store-api.cc',
   'uds-remote-store.cc',
   'worker-protocol.cc',
+  'build/child.cc',
   'build/derivation-goal.cc',
   'build/drv-output-substitution-goal.cc',
   'build/entry-points.cc',
@@ -96,6 +97,7 @@ libstore_sources = files(
 
 libstore_headers = files(
   'binary-cache-store.hh',
+  'build/child.hh',
   'build/derivation-goal.hh',
   'build/drv-output-substitution-goal.hh',
   'build/goal.hh',

src/libstore/names.cc

@@ -1,5 +1,5 @@
 #include "names.hh"
-#include "util.hh"
+#include "strings.hh"
 
 #include <regex>
 

src/libstore/nar-info-disk-cache.cc

@@ -1,7 +1,9 @@
 #include "nar-info-disk-cache.hh"
+#include "logging.hh"
 #include "sync.hh"
 #include "sqlite.hh"
 #include "globals.hh"
+#include "users.hh"
 
 #include <sqlite3.h>
 #include <nlohmann/json.hpp>

src/libstore/optimise-store.cc

@@ -1,4 +1,3 @@
-#include "util.hh"
 #include "local-store.hh"
 #include "globals.hh"
 #include "signals.hh"

src/libstore/outputs-spec.cc

@@ -1,10 +1,10 @@
 #include <regex>
 #include <nlohmann/json.hpp>
 
-#include "util.hh"
 #include "regex-combinators.hh"
 #include "outputs-spec.hh"
 #include "path-regex.hh"
+#include "strings.hh"
 
 namespace nix {
 

src/libstore/path-references.cc

@@ -1,12 +1,8 @@
 #include "path-references.hh"
 #include "hash.hh"
-#include "util.hh"
 #include "archive.hh"
 
 #include <map>
-#include <cstdlib>
-#include <mutex>
-#include <algorithm>
 
 
 namespace nix {

src/libstore/pathlocks.cc

@@ -1,10 +1,8 @@
 #include "pathlocks.hh"
-#include "util.hh"
+#include "logging.hh"
 #include "signals.hh"
-#include "sync.hh"
 
 #include <cerrno>
-#include <cstdlib>
 
 #include <fcntl.h>
 #include <sys/types.h>

src/libstore/pathlocks.hh

@@ -1,7 +1,7 @@
 #pragma once
 ///@file
 
-#include "util.hh"
+#include "file-descriptor.hh"
 
 namespace nix {
 

src/libstore/profiles.cc

@@ -1,7 +1,7 @@
 #include "profiles.hh"
 #include "store-api.hh"
 #include "local-fs-store.hh"
-#include "util.hh"
+#include "users.hh"
 
 #include <sys/types.h>
 #include <sys/stat.h>

src/libstore/remote-store.cc

@@ -1,5 +1,4 @@
 #include "serialise.hh"
-#include "util.hh"
 #include "signals.hh"
 #include "path-with-outputs.hh"
 #include "gc-store.hh"

src/libstore/serve-protocol.cc

@@ -1,11 +1,9 @@
 #include "serialise.hh"
-#include "util.hh"
 #include "path-with-outputs.hh"
 #include "store-api.hh"
 #include "build-result.hh"
 #include "serve-protocol.hh"
 #include "serve-protocol-impl.hh"
-#include "archive.hh"
 #include "path-info.hh"
 
 #include <nlohmann/json.hpp>

src/libstore/sqlite.cc

@@ -1,12 +1,11 @@
 #include "sqlite.hh"
 #include "globals.hh"
-#include "util.hh"
+#include "logging.hh"
 #include "signals.hh"
 #include "url.hh"
 
 #include <sqlite3.h>
 
-#include <atomic>
 
 namespace nix {
 

src/libstore/ssh.cc

@@ -1,5 +1,9 @@
+#include "current-process.hh"
+#include "environment-variables.hh"
 #include "ssh.hh"
 #include "finally.hh"
+#include "logging.hh"
+#include "strings.hh"
 
 namespace nix {
 

src/libstore/ssh.hh

@@ -1,7 +1,8 @@
 #pragma once
 ///@file
 
-#include "util.hh"
+#include "file-system.hh"
+#include "processes.hh"
 #include "sync.hh"
 
 namespace nix {

src/libstore/store-api.cc

@@ -1,9 +1,7 @@
-#include "crypto.hh"
 #include "fs-accessor.hh"
 #include "globals.hh"
 #include "derivations.hh"
 #include "store-api.hh"
-#include "util.hh"
 #include "nar-info-disk-cache.hh"
 #include "thread-pool.hh"
 #include "url.hh"
@@ -14,6 +12,7 @@
 // FIXME this should not be here, see TODO below on
 // `addMultipleToStore`.
 #include "worker-protocol.hh"
+#include "users.hh"
 
 #include <nlohmann/json.hpp>
 #include <regex>

src/libstore/store-api.hh

@@ -1,6 +1,7 @@
 #pragma once
 ///@file
 
+#include "logging.hh"
 #include "nar-info.hh"
 #include "realisation.hh"
 #include "path.hh"

src/libstore/uds-remote-store.cc

@@ -1,4 +1,5 @@
 #include "uds-remote-store.hh"
+#include "unix-domain-socket.hh"
 #include "worker-protocol.hh"
 
 #include <sys/types.h>

src/libstore/worker-protocol.cc

@@ -1,5 +1,4 @@
 #include "serialise.hh"
-#include "util.hh"
 #include "path-with-outputs.hh"
 #include "store-api.hh"
 #include "build-result.hh"

src/libutil/archive.cc

@@ -12,8 +12,9 @@
 #include <fcntl.h>
 
 #include "archive.hh"
-#include "util.hh"
+#include "file-system.hh"
 #include "config.hh"
+#include "logging.hh"
 #include "signals.hh"
 
 namespace nix {

src/libutil/archive.hh

@@ -3,6 +3,7 @@
 
 #include "types.hh"
 #include "serialise.hh"
+#include "file-system.hh"
 
 
 namespace nix {

src/libutil/args.cc

@@ -2,7 +2,10 @@
 #include "args/root.hh"
 #include "hash.hh"
 #include "json-utils.hh"
+#include "environment-variables.hh"
+
 #include "experimental-features-json.hh"
+#include "logging.hh"
 
 #include <glob.h>
 

src/libutil/args.hh

@@ -1,13 +1,17 @@
 #pragma once
 ///@file
 
-#include <iostream>
+#include "experimental-features.hh"
+#include "types.hh"
+#include <functional>
 #include <map>
 #include <memory>
+#include <limits>
 
 #include <nlohmann/json_fwd.hpp>
+#include <optional>
+#include <set>
 
-#include "util.hh"
 
 namespace nix {
 

src/libutil/canon-path.cc

@@ -1,5 +1,5 @@
 #include "canon-path.hh"
-#include "util.hh"
+#include "file-system.hh"
 
 namespace nix {
 

src/libutil/cgroup.cc

@@ -1,14 +1,17 @@
+#include "logging.hh"
 #if __linux__
 
 #include "cgroup.hh"
-#include "util.hh"
+#include "file-system.hh"
 #include "finally.hh"
+#include "strings.hh"
 
 #include <chrono>
 #include <cmath>
 #include <regex>
 #include <unordered_set>
 #include <thread>
+#include <signal.h>
 
 #include <dirent.h>
 #include <mntent.h>

src/libutil/comparator.hh

@@ -1,6 +1,8 @@
 #pragma once
 ///@file
 
+#include <tuple>
+
 #define DECLARE_ONE_CMP(PRE, QUAL, COMPARATOR, MY_TYPE) \
     PRE bool QUAL operator COMPARATOR(const MY_TYPE & other) const;
 #define DECLARE_EQUAL(prefix, qualification, my_type) \

src/libutil/compression.cc

@@ -1,7 +1,5 @@
 #include "compression.hh"
 #include "tarfile.hh"
-#include "util.hh"
-#include "finally.hh"
 #include "signals.hh"
 #include "logging.hh"
 
@@ -13,7 +11,6 @@
 #include <brotli/decode.h>
 #include <brotli/encode.h>
 
-#include <iostream>
 
 namespace nix {
 

src/libutil/config-impl.hh

@@ -12,7 +12,9 @@
  * instantiation.
  */
 
+#include "args.hh"
 #include "config.hh"
+#include "logging.hh"
 
 namespace nix {
 

src/libutil/config.cc

@@ -2,6 +2,9 @@
 #include "args.hh"
 #include "abstract-setting-to-json.hh"
 #include "experimental-features.hh"
+#include "file-system.hh"
+#include "logging.hh"
+#include "strings.hh"
 
 #include "config-impl.hh"
 

src/libutil/current-process.cc

@@ -0,0 +1,111 @@
+#include "current-process.hh"
+#include "error.hh"
+#include "file-system.hh"
+#include "logging.hh"
+#include "namespaces.hh"
+#include "signals.hh"
+#include "strings.hh"
+
+#ifdef __APPLE__
+# include <mach-o/dyld.h>
+#endif
+
+#if __linux__
+# include <sys/resource.h>
+#endif
+
+#include <sys/mount.h>
+#include <cgroup.hh>
+
+namespace nix {
+
+unsigned int getMaxCPU()
+{
+    #if __linux__
+    try {
+        auto cgroupFS = getCgroupFS();
+        if (!cgroupFS) return 0;
+
+        auto cgroups = getCgroups("/proc/self/cgroup");
+        auto cgroup = cgroups[""];
+        if (cgroup == "") return 0;
+
+        auto cpuFile = *cgroupFS + "/" + cgroup + "/cpu.max";
+
+        auto cpuMax = readFile(cpuFile);
+        auto cpuMaxParts = tokenizeString<std::vector<std::string>>(cpuMax, " \n");
+
+        if (cpuMaxParts.size() != 2) {
+            return 0;
+        }
+
+        auto quota = cpuMaxParts[0];
+        auto period = cpuMaxParts[1];
+        if (quota != "max")
+                return std::ceil(std::stoi(quota) / std::stof(period));
+    } catch (Error &) { ignoreException(lvlDebug); }
+    #endif
+
+    return 0;
+}
+
+rlim_t savedStackSize = 0;
+
+void setStackSize(rlim_t stackSize)
+{
+    struct rlimit limit;
+    if (getrlimit(RLIMIT_STACK, &limit) == 0 && limit.rlim_cur < stackSize) {
+        savedStackSize = limit.rlim_cur;
+        limit.rlim_cur = std::min(stackSize, limit.rlim_max);
+        if (setrlimit(RLIMIT_STACK, &limit) != 0) {
+            logger->log(
+                lvlError,
+                HintFmt(
+                    "Failed to increase stack size from %1% to %2% (maximum allowed stack size: %3%): %4%",
+                    savedStackSize,
+                    stackSize,
+                    limit.rlim_max,
+                    std::strerror(errno)
+                ).str()
+            );
+        }
+    }
+}
+
+void restoreProcessContext(bool restoreMounts)
+{
+    restoreSignals();
+    if (restoreMounts) {
+        restoreMountNamespace();
+    }
+
+    if (savedStackSize) {
+        struct rlimit limit;
+        if (getrlimit(RLIMIT_STACK, &limit) == 0) {
+            limit.rlim_cur = savedStackSize;
+            setrlimit(RLIMIT_STACK, &limit);
+        }
+    }
+}
+
+std::optional<Path> getSelfExe()
+{
+    static auto cached = []() -> std::optional<Path>
+    {
+        #if __linux__
+        return readLink("/proc/self/exe");
+        #elif __APPLE__
+        char buf[1024];
+        uint32_t size = sizeof(buf);
+        if (_NSGetExecutablePath(buf, &size) == 0)
+            return buf;
+        else
+            return std::nullopt;
+        #else
+        return std::nullopt;
+        #endif
+    }();
+    return cached;
+}
+
+}

src/libutil/current-process.hh

@@ -0,0 +1,37 @@
+#pragma once
+///@file
+
+#include <optional>
+#include <sys/resource.h>
+
+#include "types.hh"
+
+namespace nix {
+
+/**
+ * If cgroups are active, attempt to calculate the number of CPUs available.
+ * If cgroups are unavailable or if cpu.max is set to "max", return 0.
+ */
+unsigned int getMaxCPU();
+
+
+/**
+ * Change the stack size.
+ */
+void setStackSize(rlim_t stackSize);
+
+
+/**
+ * Restore the original inherited Unix process context (such as signal
+ * masks, stack size).
+
+ * See startSignalHandlerThread(), saveSignalMask().
+ */
+void restoreProcessContext(bool restoreMounts = true);
+
+/**
+ * @return the path of the current executable.
+ */
+std::optional<Path> getSelfExe();
+
+}

src/libutil/environment-variables.cc

@@ -0,0 +1,51 @@
+#include <cstring>
+#include <map>
+#include <optional>
+#include <string>
+
+extern char * * environ __attribute__((weak));
+
+namespace nix {
+
+std::optional<std::string> getEnv(const std::string & key)
+{
+    char * value = getenv(key.c_str());
+    if (!value) return {};
+    return std::string(value);
+}
+
+std::optional<std::string> getEnvNonEmpty(const std::string & key) {
+    auto value = getEnv(key);
+    if (value == "") return {};
+    return value;
+}
+
+std::map<std::string, std::string> getEnv()
+{
+    std::map<std::string, std::string> env;
+    for (size_t i = 0; environ[i]; ++i) {
+        auto s = environ[i];
+        auto eq = strchr(s, '=');
+        if (!eq)
+            // invalid env, just keep going
+            continue;
+        env.emplace(std::string(s, eq), std::string(eq + 1));
+    }
+    return env;
+}
+
+
+void clearEnv()
+{
+    for (auto & name : getEnv())
+        unsetenv(name.first.c_str());
+}
+
+void replaceEnv(const std::map<std::string, std::string> & newEnv)
+{
+    clearEnv();
+    for (auto & newEnvVar : newEnv)
+        setenv(newEnvVar.first.c_str(), newEnvVar.second.c_str(), 1);
+}
+
+}

src/libutil/environment-variables.hh

@@ -0,0 +1,42 @@
+#pragma once
+/**
+ * @file
+ *
+ * Utilities for working with the current process's environment
+ * variables.
+ */
+
+#include <map>
+#include <optional>
+#include <string>
+
+
+namespace nix {
+
+/**
+ * @return an environment variable.
+ */
+std::optional<std::string> getEnv(const std::string & key);
+
+/**
+ * @return a non empty environment variable. Returns nullopt if the env
+ * variable is set to ""
+ */
+std::optional<std::string> getEnvNonEmpty(const std::string & key);
+
+/**
+ * Get the entire environment.
+ */
+std::map<std::string, std::string> getEnv();
+
+/**
+ * Clear the environment.
+ */
+void clearEnv();
+
+/**
+ * Replace the entire environment with the given one.
+ */
+void replaceEnv(const std::map<std::string, std::string> & newEnv);
+
+}

src/libutil/error.cc

@@ -1,15 +1,15 @@
+#include "environment-variables.hh"
 #include "error.hh"
+#include "logging.hh"
 #include "position.hh"
+#include "terminal.hh"
 
 #include <iostream>
 #include <optional>
-#include "serialise.hh"
 #include <sstream>
 
 namespace nix {
 
-const std::string nativeSystem = SYSTEM;
-
 void BaseError::addTrace(std::shared_ptr<Pos> && e, HintFmt hint)
 {
     err.traces.push_front(Trace { .pos = std::move(e), .hint = hint });
@@ -415,4 +415,17 @@ std::ostream & showErrorInfo(std::ostream & out, const ErrorInfo & einfo, bool s
     return out;
 }
 
+void ignoreException(Verbosity lvl)
+{
+    /* Make sure no exceptions leave this function.
+       printError() also throws when remote is closed. */
+    try {
+        try {
+            throw;
+        } catch (std::exception & e) {
+            printMsg(lvl, "error (ignored): %1%", e.what());
+        }
+    } catch (...) { }
+}
+
 }

src/libutil/error.hh

@@ -202,4 +202,10 @@ public:
     }
 };
 
+/**
+ * Exception handling in destructors: print an error message, then
+ * ignore the exception.
+ */
+void ignoreException(Verbosity lvl = lvlError);
+
 }

src/libutil/experimental-features.cc

@@ -1,7 +1,7 @@
 #include "experimental-features.hh"
 // Required for instances of to_json and from_json for ExperimentalFeature
 #include "experimental-features-json.hh"
-#include "util.hh"
+#include "strings.hh"
 
 #include "nlohmann/json.hpp"
 

src/libutil/file-descriptor.cc

@@ -0,0 +1,252 @@
+#include "file-system.hh"
+#include "finally.hh"
+#include "logging.hh"
+#include "serialise.hh"
+#include "signals.hh"
+
+#include <fcntl.h>
+#include <unistd.h>
+
+namespace nix {
+
+std::string readFile(int fd)
+{
+    struct stat st;
+    if (fstat(fd, &st) == -1)
+        throw SysError("statting file");
+
+    return drainFD(fd, true, st.st_size);
+}
+
+
+std::string readLine(int fd)
+{
+    std::string s;
+    while (1) {
+        checkInterrupt();
+        char ch;
+        // FIXME: inefficient
+        ssize_t rd = read(fd, &ch, 1);
+        if (rd == -1) {
+            if (errno != EINTR)
+                throw SysError("reading a line");
+        } else if (rd == 0)
+            throw EndOfFile("unexpected EOF reading a line");
+        else {
+            if (ch == '\n') return s;
+            s += ch;
+        }
+    }
+}
+
+
+void writeLine(int fd, std::string s)
+{
+    s += '\n';
+    writeFull(fd, s);
+}
+
+
+void readFull(int fd, char * buf, size_t count)
+{
+    while (count) {
+        checkInterrupt();
+        ssize_t res = read(fd, buf, count);
+        if (res == -1) {
+            if (errno == EINTR) continue;
+            throw SysError("reading from file");
+        }
+        if (res == 0) throw EndOfFile("unexpected end-of-file");
+        count -= res;
+        buf += res;
+    }
+}
+
+
+void writeFull(int fd, std::string_view s, bool allowInterrupts)
+{
+    while (!s.empty()) {
+        if (allowInterrupts) checkInterrupt();
+        ssize_t res = write(fd, s.data(), s.size());
+        if (res == -1 && errno != EINTR)
+            throw SysError("writing to file");
+        if (res > 0)
+            s.remove_prefix(res);
+    }
+}
+
+
+std::string drainFD(int fd, bool block, const size_t reserveSize)
+{
+    // the parser needs two extra bytes to append terminating characters, other users will
+    // not care very much about the extra memory.
+    StringSink sink(reserveSize + 2);
+    drainFD(fd, sink, block);
+    return std::move(sink.s);
+}
+
+
+void drainFD(int fd, Sink & sink, bool block)
+{
+    // silence GCC maybe-uninitialized warning in finally
+    int saved = 0;
+
+    if (!block) {
+        saved = fcntl(fd, F_GETFL);
+        if (fcntl(fd, F_SETFL, saved | O_NONBLOCK) == -1)
+            throw SysError("making file descriptor non-blocking");
+    }
+
+    Finally finally([&]() {
+        if (!block) {
+            if (fcntl(fd, F_SETFL, saved) == -1)
+                throw SysError("making file descriptor blocking");
+        }
+    });
+
+    std::array<unsigned char, 64 * 1024> buf;
+    while (1) {
+        checkInterrupt();
+        ssize_t rd = read(fd, buf.data(), buf.size());
+        if (rd == -1) {
+            if (!block && (errno == EAGAIN || errno == EWOULDBLOCK))
+                break;
+            if (errno != EINTR)
+                throw SysError("reading from file");
+        }
+        else if (rd == 0) break;
+        else sink({(char *) buf.data(), (size_t) rd});
+    }
+}
+
+AutoCloseFD::AutoCloseFD() : fd{-1} {}
+
+
+AutoCloseFD::AutoCloseFD(int fd) : fd{fd} {}
+
+
+AutoCloseFD::AutoCloseFD(AutoCloseFD && that) : fd{that.fd}
+{
+    that.fd = -1;
+}
+
+
+AutoCloseFD & AutoCloseFD::operator =(AutoCloseFD && that)
+{
+    close();
+    fd = that.fd;
+    that.fd = -1;
+    return *this;
+}
+
+
+AutoCloseFD::~AutoCloseFD()
+{
+    try {
+        close();
+    } catch (...) {
+        ignoreException();
+    }
+}
+
+
+int AutoCloseFD::get() const
+{
+    return fd;
+}
+
+
+void AutoCloseFD::close()
+{
+    if (fd != -1) {
+        if (::close(fd) == -1)
+            /* This should never happen. */
+            throw SysError("closing file descriptor %1%", fd);
+        fd = -1;
+    }
+}
+
+void AutoCloseFD::fsync()
+{
+  if (fd != -1) {
+      int result;
+#if __APPLE__
+      result = ::fcntl(fd, F_FULLFSYNC);
+#else
+      result = ::fsync(fd);
+#endif
+      if (result == -1)
+          throw SysError("fsync file descriptor %1%", fd);
+  }
+}
+
+
+AutoCloseFD::operator bool() const
+{
+    return fd != -1;
+}
+
+
+int AutoCloseFD::release()
+{
+    int oldFD = fd;
+    fd = -1;
+    return oldFD;
+}
+
+
+void Pipe::create()
+{
+    int fds[2];
+#if HAVE_PIPE2
+    if (pipe2(fds, O_CLOEXEC) != 0) throw SysError("creating pipe");
+#else
+    if (pipe(fds) != 0) throw SysError("creating pipe");
+    closeOnExec(fds[0]);
+    closeOnExec(fds[1]);
+#endif
+    readSide = AutoCloseFD{fds[0]};
+    writeSide = AutoCloseFD{fds[1]};
+}
+
+
+void Pipe::close()
+{
+    readSide.close();
+    writeSide.close();
+}
+
+
+void closeMostFDs(const std::set<int> & exceptions)
+{
+#if __linux__
+    try {
+        for (auto & s : readDirectory("/proc/self/fd")) {
+            auto fd = std::stoi(s.name);
+            if (!exceptions.count(fd)) {
+                debug("closing leaked FD %d", fd);
+                close(fd);
+            }
+        }
+        return;
+    } catch (SysError &) {
+    }
+#endif
+
+    int maxFD = 0;
+    maxFD = sysconf(_SC_OPEN_MAX);
+    for (int fd = 0; fd < maxFD; ++fd)
+        if (!exceptions.count(fd))
+            close(fd); /* ignore result */
+}
+
+
+void closeOnExec(int fd)
+{
+    int prev;
+    if ((prev = fcntl(fd, F_GETFD, 0)) == -1 ||
+        fcntl(fd, F_SETFD, prev | FD_CLOEXEC) == -1)
+        throw SysError("setting close-on-exec flag");
+}
+
+}

src/libutil/file-descriptor.hh

@@ -0,0 +1,80 @@
+#pragma once
+///@file
+
+#include "error.hh"
+
+namespace nix {
+
+struct Sink;
+struct Source;
+
+/**
+ * Read a line from a file descriptor.
+ */
+std::string readLine(int fd);
+
+/**
+ * Write a line to a file descriptor.
+ */
+void writeLine(int fd, std::string s);
+
+/**
+ * Read the contents of a file into a string.
+ */
+std::string readFile(int fd);
+
+/**
+ * Wrappers arount read()/write() that read/write exactly the
+ * requested number of bytes.
+ */
+void readFull(int fd, char * buf, size_t count);
+void writeFull(int fd, std::string_view s, bool allowInterrupts = true);
+
+/**
+ * Read a file descriptor until EOF occurs.
+ */
+std::string drainFD(int fd, bool block = true, const size_t reserveSize=0);
+
+void drainFD(int fd, Sink & sink, bool block = true);
+
+class AutoCloseFD
+{
+    int fd;
+public:
+    AutoCloseFD();
+    explicit AutoCloseFD(int fd);
+    AutoCloseFD(const AutoCloseFD & fd) = delete;
+    AutoCloseFD(AutoCloseFD&& fd);
+    ~AutoCloseFD();
+    AutoCloseFD& operator =(const AutoCloseFD & fd) = delete;
+    AutoCloseFD& operator =(AutoCloseFD&& fd) noexcept(false);
+    int get() const;
+    explicit operator bool() const;
+    int release();
+    void close();
+    void fsync();
+    void reset() { *this = {}; }
+};
+
+class Pipe
+{
+public:
+    AutoCloseFD readSide, writeSide;
+    void create();
+    void close();
+};
+
+/**
+ * Close all file descriptors except those listed in the given set.
+ * Good practice in child processes.
+ */
+void closeMostFDs(const std::set<int> & exceptions);
+
+/**
+ * Set the close-on-exec flag for the given file descriptor.
+ */
+void closeOnExec(int fd);
+
+MakeError(EndOfFile, Error);
+
+}

src/libutil/file-system.cc

@@ -0,0 +1,670 @@
+#include <sys/time.h>
+#include <filesystem>
+#include <atomic>
+
+#include "environment-variables.hh"
+#include "file-descriptor.hh"
+#include "file-system.hh"
+#include "finally.hh"
+#include "logging.hh"
+#include "serialise.hh"
+#include "signals.hh"
+#include "types.hh"
+#include "users.hh"
+
+namespace fs = std::filesystem;
+
+namespace nix {
+
+Path absPath(Path path, std::optional<PathView> dir, bool resolveSymlinks)
+{
+    if (path.empty() || path[0] != '/') {
+        if (!dir) {
+#ifdef __GNU__
+            /* GNU (aka. GNU/Hurd) doesn't have any limitation on path
+               lengths and doesn't define `PATH_MAX'.  */
+            char *buf = getcwd(NULL, 0);
+            if (buf == NULL)
+#else
+            char buf[PATH_MAX];
+            if (!getcwd(buf, sizeof(buf)))
+#endif
+                throw SysError("cannot get cwd");
+            path = concatStrings(buf, "/", path);
+#ifdef __GNU__
+            free(buf);
+#endif
+        } else
+            path = concatStrings(*dir, "/", path);
+    }
+    return canonPath(path, resolveSymlinks);
+}
+
+
+Path canonPath(PathView path, bool resolveSymlinks)
+{
+    assert(path != "");
+
+    std::string s;
+    s.reserve(256);
+
+    if (path[0] != '/')
+        throw Error("not an absolute path: '%1%'", path);
+
+    std::string temp;
+
+    /* Count the number of times we follow a symlink and stop at some
+       arbitrary (but high) limit to prevent infinite loops. */
+    unsigned int followCount = 0, maxFollow = 1024;
+
+    while (1) {
+
+        /* Skip slashes. */
+        while (!path.empty() && path[0] == '/') path.remove_prefix(1);
+        if (path.empty()) break;
+
+        /* Ignore `.'. */
+        if (path == "." || path.substr(0, 2) == "./")
+            path.remove_prefix(1);
+
+        /* If `..', delete the last component. */
+        else if (path == ".." || path.substr(0, 3) == "../")
+        {
+            if (!s.empty()) s.erase(s.rfind('/'));
+            path.remove_prefix(2);
+        }
+
+        /* Normal component; copy it. */
+        else {
+            s += '/';
+            if (const auto slash = path.find('/'); slash == std::string::npos) {
+                s += path;
+                path = {};
+            } else {
+                s += path.substr(0, slash);
+                path = path.substr(slash);
+            }
+
+            /* If s points to a symlink, resolve it and continue from there */
+            if (resolveSymlinks && isLink(s)) {
+                if (++followCount >= maxFollow)
+                    throw Error("infinite symlink recursion in path '%1%'", path);
+                temp = concatStrings(readLink(s), path);
+                path = temp;
+                if (!temp.empty() && temp[0] == '/') {
+                    s.clear();  /* restart for symlinks pointing to absolute path */
+                } else {
+                    s = dirOf(s);
+                    if (s == "/") {  // we don’t want trailing slashes here, which dirOf only produces if s = /
+                        s.clear();
+                    }
+                }
+            }
+        }
+    }
+
+    return s.empty() ? "/" : std::move(s);
+}
+
+void chmodPath(const Path & path, mode_t mode)
+{
+    if (chmod(path.c_str(), mode) == -1)
+        throw SysError("setting permissions on '%s'", path);
+}
+
+Path dirOf(const PathView path)
+{
+    Path::size_type pos = path.rfind('/');
+    if (pos == std::string::npos)
+        return ".";
+    return pos == 0 ? "/" : Path(path, 0, pos);
+}
+
+
+std::string_view baseNameOf(std::string_view path)
+{
+    if (path.empty())
+        return "";
+
+    auto last = path.size() - 1;
+    if (path[last] == '/' && last > 0)
+        last -= 1;
+
+    auto pos = path.rfind('/', last);
+    if (pos == std::string::npos)
+        pos = 0;
+    else
+        pos += 1;
+
+    return path.substr(pos, last - pos + 1);
+}
+
+
+std::string expandTilde(std::string_view path)
+{
+    // TODO: expand ~user ?
+    auto tilde = path.substr(0, 2);
+    if (tilde == "~/" || tilde == "~")
+        return getHome() + std::string(path.substr(1));
+    else
+        return std::string(path);
+}
+
+
+bool isInDir(std::string_view path, std::string_view dir)
+{
+    return path.substr(0, 1) == "/"
+        && path.substr(0, dir.size()) == dir
+        && path.size() >= dir.size() + 2
+        && path[dir.size()] == '/';
+}
+
+
+bool isDirOrInDir(std::string_view path, std::string_view dir)
+{
+    return path == dir || isInDir(path, dir);
+}
+
+
+struct stat stat(const Path & path)
+{
+    struct stat st;
+    if (stat(path.c_str(), &st))
+        throw SysError("getting status of '%1%'", path);
+    return st;
+}
+
+
+struct stat lstat(const Path & path)
+{
+    struct stat st;
+    if (lstat(path.c_str(), &st))
+        throw SysError("getting status of '%1%'", path);
+    return st;
+}
+
+std::optional<struct stat> maybeLstat(const Path & path)
+{
+    std::optional<struct stat> st{std::in_place};
+    if (lstat(path.c_str(), &*st))
+    {
+        if (errno == ENOENT || errno == ENOTDIR)
+            st.reset();
+        else
+            throw SysError("getting status of '%s'", path);
+    }
+    return st;
+}
+
+bool pathExists(const Path & path)
+{
+    return maybeLstat(path).has_value();
+}
+
+bool pathAccessible(const Path & path)
+{
+    try {
+        return pathExists(path);
+    } catch (SysError & e) {
+        // swallow EPERM
+        if (e.errNo == EPERM) return false;
+        throw;
+    }
+}
+
+
+Path readLink(const Path & path)
+{
+    checkInterrupt();
+    std::vector<char> buf;
+    for (ssize_t bufSize = PATH_MAX/4; true; bufSize += bufSize/2) {
+        buf.resize(bufSize);
+        ssize_t rlSize = readlink(path.c_str(), buf.data(), bufSize);
+        if (rlSize == -1)
+            if (errno == EINVAL)
+                throw Error("'%1%' is not a symlink", path);
+            else
+                throw SysError("reading symbolic link '%1%'", path);
+        else if (rlSize < bufSize)
+            return std::string(buf.data(), rlSize);
+    }
+}
+
+
+bool isLink(const Path & path)
+{
+    struct stat st = lstat(path);
+    return S_ISLNK(st.st_mode);
+}
+
+
+DirEntries readDirectory(DIR *dir, const Path & path)
+{
+    DirEntries entries;
+    entries.reserve(64);
+
+    struct dirent * dirent;
+    while (errno = 0, dirent = readdir(dir)) { /* sic */
+        checkInterrupt();
+        std::string name = dirent->d_name;
+        if (name == "." || name == "..") continue;
+        entries.emplace_back(name, dirent->d_ino,
+#ifdef HAVE_STRUCT_DIRENT_D_TYPE
+            dirent->d_type
+#else
+            DT_UNKNOWN
+#endif
+        );
+    }
+    if (errno) throw SysError("reading directory '%1%'", path);
+
+    return entries;
+}
+
+DirEntries readDirectory(const Path & path)
+{
+    AutoCloseDir dir(opendir(path.c_str()));
+    if (!dir) throw SysError("opening directory '%1%'", path);
+
+    return readDirectory(dir.get(), path);
+}
+
+
+unsigned char getFileType(const Path & path)
+{
+    struct stat st = lstat(path);
+    if (S_ISDIR(st.st_mode)) return DT_DIR;
+    if (S_ISLNK(st.st_mode)) return DT_LNK;
+    if (S_ISREG(st.st_mode)) return DT_REG;
+    return DT_UNKNOWN;
+}
+
+
+std::string readFile(const Path & path)
+{
+    AutoCloseFD fd{open(path.c_str(), O_RDONLY | O_CLOEXEC)};
+    if (!fd)
+        throw SysError("opening file '%1%'", path);
+    return readFile(fd.get());
+}
+
+
+void readFile(const Path & path, Sink & sink)
+{
+    AutoCloseFD fd{open(path.c_str(), O_RDONLY | O_CLOEXEC)};
+    if (!fd)
+        throw SysError("opening file '%s'", path);
+    drainFD(fd.get(), sink);
+}
+
+
+void writeFile(const Path & path, std::string_view s, mode_t mode, bool sync)
+{
+    AutoCloseFD fd{open(path.c_str(), O_WRONLY | O_TRUNC | O_CREAT | O_CLOEXEC, mode)};
+    if (!fd)
+        throw SysError("opening file '%1%'", path);
+    try {
+        writeFull(fd.get(), s);
+    } catch (Error & e) {
+        e.addTrace({}, "writing file '%1%'", path);
+        throw;
+    }
+    if (sync)
+        fd.fsync();
+    // Explicitly close to make sure exceptions are propagated.
+    fd.close();
+    if (sync)
+        syncParent(path);
+}
+
+
+void writeFile(const Path & path, Source & source, mode_t mode, bool sync)
+{
+    AutoCloseFD fd{open(path.c_str(), O_WRONLY | O_TRUNC | O_CREAT | O_CLOEXEC, mode)};
+    if (!fd)
+        throw SysError("opening file '%1%'", path);
+
+    std::vector<char> buf(64 * 1024);
+
+    try {
+        while (true) {
+            try {
+                auto n = source.read(buf.data(), buf.size());
+                writeFull(fd.get(), {buf.data(), n});
+            } catch (EndOfFile &) { break; }
+        }
+    } catch (Error & e) {
+        e.addTrace({}, "writing file '%1%'", path);
+        throw;
+    }
+    if (sync)
+        fd.fsync();
+    // Explicitly close to make sure exceptions are propagated.
+    fd.close();
+    if (sync)
+        syncParent(path);
+}
+
+void syncParent(const Path & path)
+{
+    AutoCloseFD fd{open(dirOf(path).c_str(), O_RDONLY, 0)};
+    if (!fd)
+        throw SysError("opening file '%1%'", path);
+    fd.fsync();
+}
+
+static void _deletePath(int parentfd, const Path & path, uint64_t & bytesFreed)
+{
+    checkInterrupt();
+
+    std::string name(baseNameOf(path));
+
+    struct stat st;
+    if (fstatat(parentfd, name.c_str(), &st, AT_SYMLINK_NOFOLLOW) == -1) {
+        if (errno == ENOENT) return;
+        throw SysError("getting status of '%1%'", path);
+    }
+
+    if (!S_ISDIR(st.st_mode)) {
+        /* We are about to delete a file. Will it likely free space? */
+
+        switch (st.st_nlink) {
+            /* Yes: last link. */
+            case 1:
+                bytesFreed += st.st_size;
+                break;
+            /* Maybe: yes, if 'auto-optimise-store' or manual optimisation
+               was performed. Instead of checking for real let's assume
+               it's an optimised file and space will be freed.
+
+               In worst case we will double count on freed space for files
+               with exactly two hardlinks for unoptimised packages.
+             */
+            case 2:
+                bytesFreed += st.st_size;
+                break;
+            /* No: 3+ links. */
+            default:
+                break;
+        }
+    }
+
+    if (S_ISDIR(st.st_mode)) {
+        /* Make the directory accessible. */
+        const auto PERM_MASK = S_IRUSR | S_IWUSR | S_IXUSR;
+        if ((st.st_mode & PERM_MASK) != PERM_MASK) {
+            if (fchmodat(parentfd, name.c_str(), st.st_mode | PERM_MASK, 0) == -1)
+                throw SysError("chmod '%1%'", path);
+        }
+
+        int fd = openat(parentfd, path.c_str(), O_RDONLY);
+        if (fd == -1)
+            throw SysError("opening directory '%1%'", path);
+        AutoCloseDir dir(fdopendir(fd));
+        if (!dir)
+            throw SysError("opening directory '%1%'", path);
+        for (auto & i : readDirectory(dir.get(), path))
+            _deletePath(dirfd(dir.get()), path + "/" + i.name, bytesFreed);
+    }
+
+    int flags = S_ISDIR(st.st_mode) ? AT_REMOVEDIR : 0;
+    if (unlinkat(parentfd, name.c_str(), flags) == -1) {
+        if (errno == ENOENT) return;
+        throw SysError("cannot unlink '%1%'", path);
+    }
+}
+
+static void _deletePath(const Path & path, uint64_t & bytesFreed)
+{
+    Path dir = dirOf(path);
+    if (dir == "")
+        dir = "/";
+
+    AutoCloseFD dirfd{open(dir.c_str(), O_RDONLY)};
+    if (!dirfd) {
+        if (errno == ENOENT) return;
+        throw SysError("opening directory '%1%'", path);
+    }
+
+    _deletePath(dirfd.get(), path, bytesFreed);
+}
+
+
+void deletePath(const Path & path)
+{
+    uint64_t dummy;
+    deletePath(path, dummy);
+}
+
+
+void deletePath(const Path & path, uint64_t & bytesFreed)
+{
+    //Activity act(*logger, lvlDebug, "recursively deleting path '%1%'", path);
+    bytesFreed = 0;
+    _deletePath(path, bytesFreed);
+}
+
+Paths createDirs(const Path & path)
+{
+    Paths created;
+    if (path == "/") return created;
+
+    struct stat st;
+    if (lstat(path.c_str(), &st) == -1) {
+        created = createDirs(dirOf(path));
+        if (mkdir(path.c_str(), 0777) == -1 && errno != EEXIST)
+            throw SysError("creating directory '%1%'", path);
+        st = lstat(path);
+        created.push_back(path);
+    }
+
+    if (S_ISLNK(st.st_mode) && stat(path.c_str(), &st) == -1)
+        throw SysError("statting symlink '%1%'", path);
+
+    if (!S_ISDIR(st.st_mode)) throw Error("'%1%' is not a directory", path);
+
+    return created;
+}
+
+
+//////////////////////////////////////////////////////////////////////
+
+AutoDelete::AutoDelete() : del{false} {}
+
+AutoDelete::AutoDelete(const std::string & p, bool recursive) : path(p)
+{
+    del = true;
+    this->recursive = recursive;
+}
+
+AutoDelete::~AutoDelete()
+{
+    try {
+        if (del) {
+            if (recursive)
+                deletePath(path);
+            else {
+                if (remove(path.c_str()) == -1)
+                    throw SysError("cannot unlink '%1%'", path);
+            }
+        }
+    } catch (...) {
+        ignoreException();
+    }
+}
+
+void AutoDelete::cancel()
+{
+    del = false;
+}
+
+void AutoDelete::reset(const Path & p, bool recursive) {
+    path = p;
+    this->recursive = recursive;
+    del = true;
+}
+
+//////////////////////////////////////////////////////////////////////
+
+static Path tempName(Path tmpRoot, const Path & prefix, bool includePid,
+    std::atomic<unsigned int> & counter)
+{
+    tmpRoot = canonPath(tmpRoot.empty() ? getEnv("TMPDIR").value_or("/tmp") : tmpRoot, true);
+    if (includePid)
+        return fmt("%1%/%2%-%3%-%4%", tmpRoot, prefix, getpid(), counter++);
+    else
+        return fmt("%1%/%2%-%3%", tmpRoot, prefix, counter++);
+}
+
+Path createTempDir(const Path & tmpRoot, const Path & prefix,
+    bool includePid, bool useGlobalCounter, mode_t mode)
+{
+    static std::atomic<unsigned int> globalCounter = 0;
+    std::atomic<unsigned int> localCounter = 0;
+    auto & counter(useGlobalCounter ? globalCounter : localCounter);
+
+    while (1) {
+        checkInterrupt();
+        Path tmpDir = tempName(tmpRoot, prefix, includePid, counter);
+        if (mkdir(tmpDir.c_str(), mode) == 0) {
+#if __FreeBSD__
+            /* Explicitly set the group of the directory.  This is to
+               work around around problems caused by BSD's group
+               ownership semantics (directories inherit the group of
+               the parent).  For instance, the group of /tmp on
+               FreeBSD is "wheel", so all directories created in /tmp
+               will be owned by "wheel"; but if the user is not in
+               "wheel", then "tar" will fail to unpack archives that
+               have the setgid bit set on directories. */
+            if (chown(tmpDir.c_str(), (uid_t) -1, getegid()) != 0)
+                throw SysError("setting group of directory '%1%'", tmpDir);
+#endif
+            return tmpDir;
+        }
+        if (errno != EEXIST)
+            throw SysError("creating directory '%1%'", tmpDir);
+    }
+}
+
+
+std::pair<AutoCloseFD, Path> createTempFile(const Path & prefix)
+{
+    Path tmpl(getEnv("TMPDIR").value_or("/tmp") + "/" + prefix + ".XXXXXX");
+    // Strictly speaking, this is UB, but who cares...
+    // FIXME: use O_TMPFILE.
+    AutoCloseFD fd(mkstemp((char *) tmpl.c_str()));
+    if (!fd)
+        throw SysError("creating temporary file '%s'", tmpl);
+    closeOnExec(fd.get());
+    return {std::move(fd), tmpl};
+}
+
+void createSymlink(const Path & target, const Path & link)
+{
+    if (symlink(target.c_str(), link.c_str()))
+        throw SysError("creating symlink from '%1%' to '%2%'", link, target);
+}
+
+void replaceSymlink(const Path & target, const Path & link)
+{
+    for (unsigned int n = 0; true; n++) {
+        Path tmp = canonPath(fmt("%s/.%d_%s", dirOf(link), n, baseNameOf(link)));
+
+        try {
+            createSymlink(target, tmp);
+        } catch (SysError & e) {
+            if (e.errNo == EEXIST) continue;
+            throw;
+        }
+
+        renameFile(tmp, link);
+
+        break;
+    }
+}
+
+void setWriteTime(const fs::path & p, const struct stat & st)
+{
+    struct timeval times[2];
+    times[0] = {
+        .tv_sec = st.st_atime,
+        .tv_usec = 0,
+    };
+    times[1] = {
+        .tv_sec = st.st_mtime,
+        .tv_usec = 0,
+    };
+    if (lutimes(p.c_str(), times) != 0)
+        throw SysError("changing modification time of '%s'", p);
+}
+
+void copy(const fs::directory_entry & from, const fs::path & to, CopyFileFlags flags)
+{
+    // TODO: Rewrite the `is_*` to use `symlink_status()`
+    auto statOfFrom = lstat(from.path().c_str());
+    auto fromStatus = from.symlink_status();
+
+    // Mark the directory as writable so that we can delete its children
+    if (flags.deleteAfter && fs::is_directory(fromStatus)) {
+        fs::permissions(from.path(), fs::perms::owner_write, fs::perm_options::add | fs::perm_options::nofollow);
+    }
+
+
+    if (fs::is_symlink(fromStatus) || fs::is_regular_file(fromStatus)) {
+        auto opts = fs::copy_options::overwrite_existing;
+
+        if (!flags.followSymlinks) {
+            opts |= fs::copy_options::copy_symlinks;
+        }
+
+        fs::copy(from.path(), to, opts);
+    } else if (fs::is_directory(fromStatus)) {
+        fs::create_directory(to);
+        for (auto & entry : fs::directory_iterator(from.path())) {
+            copy(entry, to / entry.path().filename(), flags);
+        }
+    } else {
+        throw Error("file '%s' has an unsupported type", from.path());
+    }
+
+    setWriteTime(to, statOfFrom);
+    if (flags.deleteAfter) {
+        if (!fs::is_symlink(fromStatus))
+            fs::permissions(from.path(), fs::perms::owner_write, fs::perm_options::add | fs::perm_options::nofollow);
+        fs::remove(from.path());
+    }
+}
+
+
+void copyFile(const Path & oldPath, const Path & newPath, CopyFileFlags flags)
+{
+    return copy(fs::directory_entry(fs::path(oldPath)), fs::path(newPath), flags);
+}
+
+void renameFile(const Path & oldName, const Path & newName)
+{
+    fs::rename(oldName, newName);
+}
+
+void moveFile(const Path & oldName, const Path & newName)
+{
+    try {
+        renameFile(oldName, newName);
+    } catch (fs::filesystem_error & e) {
+        auto oldPath = fs::path(oldName);
+        auto newPath = fs::path(newName);
+        // For the move to be as atomic as possible, copy to a temporary
+        // directory
+        fs::path temp = createTempDir(newPath.parent_path(), "rename-tmp");
+        Finally removeTemp = [&]() { fs::remove(temp); };
+        auto tempCopyTarget = temp / "copy-target";
+        if (e.code().value() == EXDEV) {
+            fs::remove(newPath);
+            warn("Can’t rename %s as %s, copying instead", oldName, newName);
+            copy(fs::directory_entry(oldPath), tempCopyTarget, { .deleteAfter = true });
+            renameFile(tempCopyTarget, newPath);
+        }
+    }
+}
+
+}

src/libutil/file-system.hh

@@ -0,0 +1,269 @@
+#pragma once
+/**
+ * @file
+ *
+ * Utiltities for working with the file sytem and file paths.
+ */
+
+#include "types.hh"
+#include "file-descriptor.hh"
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <dirent.h>
+#include <unistd.h>
+
+#include <boost/lexical_cast.hpp>
+
+#include <functional>
+#include <optional>
+
+#ifndef HAVE_STRUCT_DIRENT_D_TYPE
+#define DT_UNKNOWN 0
+#define DT_REG 1
+#define DT_LNK 2
+#define DT_DIR 3
+#endif
+
+namespace nix {
+
+struct Sink;
+struct Source;
+
+/**
+ * @return An absolutized path, resolving paths relative to the
+ * specified directory, or the current directory otherwise.  The path
+ * is also canonicalised.
+ */
+Path absPath(Path path,
+    std::optional<PathView> dir = {},
+    bool resolveSymlinks = false);
+
+/**
+ * Canonicalise a path by removing all `.` or `..` components and
+ * double or trailing slashes.  Optionally resolves all symlink
+ * components such that each component of the resulting path is *not*
+ * a symbolic link.
+ */
+Path canonPath(PathView path, bool resolveSymlinks = false);
+
+/**
+ * Change the permissions of a path
+ * Not called `chmod` as it shadows and could be confused with
+ * `int chmod(char *, mode_t)`, which does not handle errors
+ */
+void chmodPath(const Path & path, mode_t mode);
+
+/**
+ * @return The directory part of the given canonical path, i.e.,
+ * everything before the final `/`.  If the path is the root or an
+ * immediate child thereof (e.g., `/foo`), this means `/`
+ * is returned.
+ */
+Path dirOf(const PathView path);
+
+/**
+ * @return the base name of the given canonical path, i.e., everything
+ * following the final `/` (trailing slashes are removed).
+ */
+std::string_view baseNameOf(std::string_view path);
+
+/**
+ * Perform tilde expansion on a path.
+ */
+std::string expandTilde(std::string_view path);
+
+/**
+ * Check whether 'path' is a descendant of 'dir'. Both paths must be
+ * canonicalized.
+ */
+bool isInDir(std::string_view path, std::string_view dir);
+
+/**
+ * Check whether 'path' is equal to 'dir' or a descendant of
+ * 'dir'. Both paths must be canonicalized.
+ */
+bool isDirOrInDir(std::string_view path, std::string_view dir);
+
+/**
+ * Get status of `path`.
+ */
+struct stat stat(const Path & path);
+struct stat lstat(const Path & path);
+
+/**
+ * `lstat` the given path if it exists.
+ * @return std::nullopt if the path doesn't exist, or an optional containing the result of `lstat` otherwise
+ */
+std::optional<struct stat> maybeLstat(const Path & path);
+
+/**
+ * @return true iff the given path exists.
+ */
+bool pathExists(const Path & path);
+
+/**
+ * A version of pathExists that returns false on a permission error.
+ * Useful for inferring default paths across directories that might not
+ * be readable.
+ * @return true iff the given path can be accessed and exists
+ */
+bool pathAccessible(const Path & path);
+
+/**
+ * Read the contents (target) of a symbolic link.  The result is not
+ * in any way canonicalised.
+ */
+Path readLink(const Path & path);
+
+bool isLink(const Path & path);
+
+/**
+ * Read the contents of a directory.  The entries `.` and `..` are
+ * removed.
+ */
+struct DirEntry
+{
+    std::string name;
+    ino_t ino;
+    /**
+     * one of DT_*
+     */
+    unsigned char type;
+    DirEntry(std::string name, ino_t ino, unsigned char type)
+        : name(std::move(name)), ino(ino), type(type) { }
+};
+
+typedef std::vector<DirEntry> DirEntries;
+
+DirEntries readDirectory(const Path & path);
+
+unsigned char getFileType(const Path & path);
+
+/**
+ * Read the contents of a file into a string.
+ */
+std::string readFile(const Path & path);
+void readFile(const Path & path, Sink & sink);
+
+/**
+ * Write a string to a file.
+ */
+void writeFile(const Path & path, std::string_view s, mode_t mode = 0666, bool sync = false);
+
+void writeFile(const Path & path, Source & source, mode_t mode = 0666, bool sync = false);
+
+/**
+ * Flush a file's parent directory to disk
+ */
+void syncParent(const Path & path);
+
+/**
+ * Delete a path; i.e., in the case of a directory, it is deleted
+ * recursively. It's not an error if the path does not exist. The
+ * second variant returns the number of bytes and blocks freed.
+ */
+void deletePath(const Path & path);
+
+void deletePath(const Path & path, uint64_t & bytesFreed);
+
+/**
+ * Create a directory and all its parents, if necessary.  Returns the
+ * list of created directories, in order of creation.
+ */
+Paths createDirs(const Path & path);
+inline Paths createDirs(PathView path)
+{
+    return createDirs(Path(path));
+}
+
+/**
+ * Create a symlink.
+ */
+void createSymlink(const Path & target, const Path & link);
+
+/**
+ * Atomically create or replace a symlink.
+ */
+void replaceSymlink(const Path & target, const Path & link);
+
+void renameFile(const Path & src, const Path & dst);
+
+/**
+ * Similar to 'renameFile', but fallback to a copy+remove if `src` and `dst`
+ * are on a different filesystem.
+ *
+ * Beware that this might not be atomic because of the copy that happens behind
+ * the scenes
+ */
+void moveFile(const Path & src, const Path & dst);
+
+struct CopyFileFlags
+{
+    /**
+     * Delete the file after copying.
+     */
+    bool deleteAfter = false;
+
+    /**
+     * Follow symlinks and copy the eventual target.
+     */
+    bool followSymlinks = false;
+};
+
+/**
+ * Recursively copy the content of `oldPath` to `newPath`. If `andDelete` is
+ * `true`, then also remove `oldPath` (making this equivalent to `moveFile`, but
+ * with the guaranty that the destination will be “fresh”, with no stale inode
+ * or file descriptor pointing to it).
+ */
+void copyFile(const Path & oldPath, const Path & newPath, CopyFileFlags flags);
+
+/**
+ * Automatic cleanup of resources.
+ */
+
+
+class AutoDelete
+{
+    Path path;
+    bool del;
+    bool recursive;
+public:
+    AutoDelete();
+    AutoDelete(const Path & p, bool recursive = true);
+    ~AutoDelete();
+    void cancel();
+    void reset(const Path & p, bool recursive = true);
+    operator Path() const { return path; }
+    operator PathView() const { return path; }
+};
+
+struct DIRDeleter
+{
+    void operator()(DIR * dir) const {
+        closedir(dir);
+    }
+};
+
+typedef std::unique_ptr<DIR, DIRDeleter> AutoCloseDir;
+
+/**
+ * Create a temporary directory.
+ */
+Path createTempDir(const Path & tmpRoot = "", const Path & prefix = "nix",
+    bool includePid = true, bool useGlobalCounter = true, mode_t mode = 0755);
+
+/**
+ * Create a temporary file, returning a file handle and its path.
+ */
+std::pair<AutoCloseFD, Path> createTempFile(const Path & prefix = "nix");
+
+/**
+ * Used in various places.
+ */
+typedef std::function<bool(const Path & path)> PathFilter;
+
+extern PathFilter defaultPathFilter;
+
+}

src/libutil/filesystem.cc

@@ -1,175 +0,0 @@
-#include <sys/time.h>
-#include <filesystem>
-#include <atomic>
-
-#include "finally.hh"
-#include "util.hh"
-#include "signals.hh"
-#include "types.hh"
-
-namespace fs = std::filesystem;
-
-namespace nix {
-
-static Path tempName(Path tmpRoot, const Path & prefix, bool includePid,
-    std::atomic<unsigned int> & counter)
-{
-    tmpRoot = canonPath(tmpRoot.empty() ? getEnv("TMPDIR").value_or("/tmp") : tmpRoot, true);
-    if (includePid)
-        return fmt("%1%/%2%-%3%-%4%", tmpRoot, prefix, getpid(), counter++);
-    else
-        return fmt("%1%/%2%-%3%", tmpRoot, prefix, counter++);
-}
-
-Path createTempDir(const Path & tmpRoot, const Path & prefix,
-    bool includePid, bool useGlobalCounter, mode_t mode)
-{
-    static std::atomic<unsigned int> globalCounter = 0;
-    std::atomic<unsigned int> localCounter = 0;
-    auto & counter(useGlobalCounter ? globalCounter : localCounter);
-
-    while (1) {
-        checkInterrupt();
-        Path tmpDir = tempName(tmpRoot, prefix, includePid, counter);
-        if (mkdir(tmpDir.c_str(), mode) == 0) {
-#if __FreeBSD__
-            /* Explicitly set the group of the directory.  This is to
-               work around around problems caused by BSD's group
-               ownership semantics (directories inherit the group of
-               the parent).  For instance, the group of /tmp on
-               FreeBSD is "wheel", so all directories created in /tmp
-               will be owned by "wheel"; but if the user is not in
-               "wheel", then "tar" will fail to unpack archives that
-               have the setgid bit set on directories. */
-            if (chown(tmpDir.c_str(), (uid_t) -1, getegid()) != 0)
-                throw SysError("setting group of directory '%1%'", tmpDir);
-#endif
-            return tmpDir;
-        }
-        if (errno != EEXIST)
-            throw SysError("creating directory '%1%'", tmpDir);
-    }
-}
-
-
-std::pair<AutoCloseFD, Path> createTempFile(const Path & prefix)
-{
-    Path tmpl(getEnv("TMPDIR").value_or("/tmp") + "/" + prefix + ".XXXXXX");
-    // Strictly speaking, this is UB, but who cares...
-    // FIXME: use O_TMPFILE.
-    AutoCloseFD fd(mkstemp((char *) tmpl.c_str()));
-    if (!fd)
-        throw SysError("creating temporary file '%s'", tmpl);
-    closeOnExec(fd.get());
-    return {std::move(fd), tmpl};
-}
-
-void createSymlink(const Path & target, const Path & link)
-{
-    if (symlink(target.c_str(), link.c_str()))
-        throw SysError("creating symlink from '%1%' to '%2%'", link, target);
-}
-
-void replaceSymlink(const Path & target, const Path & link)
-{
-    for (unsigned int n = 0; true; n++) {
-        Path tmp = canonPath(fmt("%s/.%d_%s", dirOf(link), n, baseNameOf(link)));
-
-        try {
-            createSymlink(target, tmp);
-        } catch (SysError & e) {
-            if (e.errNo == EEXIST) continue;
-            throw;
-        }
-
-        renameFile(tmp, link);
-
-        break;
-    }
-}
-
-void setWriteTime(const fs::path & p, const struct stat & st)
-{
-    struct timeval times[2];
-    times[0] = {
-        .tv_sec = st.st_atime,
-        .tv_usec = 0,
-    };
-    times[1] = {
-        .tv_sec = st.st_mtime,
-        .tv_usec = 0,
-    };
-    if (lutimes(p.c_str(), times) != 0)
-        throw SysError("changing modification time of '%s'", p);
-}
-
-void copy(const fs::directory_entry & from, const fs::path & to, CopyFileFlags flags)
-{
-    // TODO: Rewrite the `is_*` to use `symlink_status()`
-    auto statOfFrom = lstat(from.path().c_str());
-    auto fromStatus = from.symlink_status();
-
-    // Mark the directory as writable so that we can delete its children
-    if (flags.deleteAfter && fs::is_directory(fromStatus)) {
-        fs::permissions(from.path(), fs::perms::owner_write, fs::perm_options::add | fs::perm_options::nofollow);
-    }
-
-
-    if (fs::is_symlink(fromStatus) || fs::is_regular_file(fromStatus)) {
-        auto opts = fs::copy_options::overwrite_existing;
-
-        if (!flags.followSymlinks) {
-            opts |= fs::copy_options::copy_symlinks;
-        }
-
-        fs::copy(from.path(), to, opts);
-    } else if (fs::is_directory(fromStatus)) {
-        fs::create_directory(to);
-        for (auto & entry : fs::directory_iterator(from.path())) {
-            copy(entry, to / entry.path().filename(), flags);
-        }
-    } else {
-        throw Error("file '%s' has an unsupported type", from.path());
-    }
-
-    setWriteTime(to, statOfFrom);
-    if (flags.deleteAfter) {
-        if (!fs::is_symlink(fromStatus))
-            fs::permissions(from.path(), fs::perms::owner_write, fs::perm_options::add | fs::perm_options::nofollow);
-        fs::remove(from.path());
-    }
-}
-
-
-void copyFile(const Path & oldPath, const Path & newPath, CopyFileFlags flags)
-{
-    return copy(fs::directory_entry(fs::path(oldPath)), fs::path(newPath), flags);
-}
-
-void renameFile(const Path & oldName, const Path & newName)
-{
-    fs::rename(oldName, newName);
-}
-
-void moveFile(const Path & oldName, const Path & newName)
-{
-    try {
-        renameFile(oldName, newName);
-    } catch (fs::filesystem_error & e) {
-        auto oldPath = fs::path(oldName);
-        auto newPath = fs::path(newName);
-        // For the move to be as atomic as possible, copy to a temporary
-        // directory
-        fs::path temp = createTempDir(newPath.parent_path(), "rename-tmp");
-        Finally removeTemp = [&]() { fs::remove(temp); };
-        auto tempCopyTarget = temp / "copy-target";
-        if (e.code().value() == EXDEV) {
-            fs::remove(newPath);
-            warn("Can’t rename %s as %s, copying instead", oldName, newName);
-            copy(fs::directory_entry(oldPath), tempCopyTarget, { .deleteAfter = true });
-            renameFile(tempCopyTarget, newPath);
-        }
-    }
-}
-
-}

src/libutil/hash.cc

@@ -1,4 +1,3 @@
-#include <iostream>
 #include <cstring>
 
 #include <openssl/crypto.h>
@@ -8,8 +7,8 @@
 #include "args.hh"
 #include "hash.hh"
 #include "archive.hh"
+#include "logging.hh"
 #include "split.hh"
-#include "util.hh"
 
 #include <sys/types.h>
 #include <sys/stat.h>

src/libutil/hash.hh

@@ -3,6 +3,7 @@
 
 #include "types.hh"
 #include "serialise.hh"
+#include "file-system.hh"
 
 
 namespace nix {