Assorted windows fixes for libutil, HANDLEs and path handling

src/libutil-tests/file-system.cc

@@ -388,14 +388,13 @@ TEST(openFileEnsureBeneathNoSymlinks, works)
 TEST(createAnonymousTempFile, works)
 {
     auto fd = createAnonymousTempFile();
-    auto fd_ = fromDescriptorReadOnly(fd.get());
     writeFull(fd.get(), "test");
-    lseek(fd_, 0, SEEK_SET);
+    lseek(fd.get(), 0, SEEK_SET);
     FdSource source{fd.get()};
     EXPECT_EQ(source.drain(), "test");
-    lseek(fd_, 0, SEEK_END);
+    lseek(fd.get(), 0, SEEK_END);
     writeFull(fd.get(), "test");
-    lseek(fd_, 0, SEEK_SET);
+    lseek(fd.get(), 0, SEEK_SET);
     EXPECT_EQ(source.drain(), "testtest");
 }
 
@@ -406,14 +405,20 @@ TEST(createAnonymousTempFile, works)
 TEST(FdSource, restartWorks)
 {
     auto fd = createAnonymousTempFile();
-    auto fd_ = fromDescriptorReadOnly(fd.get());
     writeFull(fd.get(), "hello world");
-    lseek(fd_, 0, SEEK_SET);
+    lseek(fd.get(), 0, SEEK_SET);
     FdSource source{fd.get()};
     EXPECT_EQ(source.drain(), "hello world");
     source.restart();
     EXPECT_EQ(source.drain(), "hello world");
     EXPECT_EQ(source.drain(), "");
 }
 
+TEST(createTempDir, works)
+{
+    auto tmpDir = createTempDir();
+    nix::AutoDelete delTmpDir(tmpDir, /*recursive=*/true);
+    ASSERT_TRUE(std::filesystem::is_directory(tmpDir));
+}
+
 } // namespace nix

src/libutil/file-system.cc

@@ -115,9 +115,6 @@ Path canonPath(PathView path, bool resolveSymlinks)
     if (!isAbsolute(path))
         throw Error("not an absolute path: '%1%'", path);
 
-    // For Windows
-    auto rootName = std::filesystem::path{path}.root_name();
-
     /* This just exists because we cannot set the target of `remaining`
        (the callback parameter) directly to a newly-constructed string,
        since it is `std::string_view`. */
@@ -147,8 +144,6 @@ Path canonPath(PathView path, bool resolveSymlinks)
             }
         });
 
-    if (!rootName.empty())
-        ret = rootName.string() + std::move(ret);
     return ret;
 }
 
@@ -380,14 +375,6 @@ void syncParent(const Path & path)
     fd.fsync();
 }
 
-#ifdef __FreeBSD__
-#  define MOUNTEDPATHS_PARAM , std::set<Path> & mountedPaths
-#  define MOUNTEDPATHS_ARG , mountedPaths
-#else
-#  define MOUNTEDPATHS_PARAM
-#  define MOUNTEDPATHS_ARG
-#endif
-
 void recursiveSync(const Path & path)
 {
     /* If it's a file or symlink, just fsync and return. */
@@ -432,129 +419,6 @@ void recursiveSync(const Path & path)
     }
 }
 
-static void _deletePath(
-    Descriptor parentfd,
-    const std::filesystem::path & path,
-    uint64_t & bytesFreed,
-    std::exception_ptr & ex MOUNTEDPATHS_PARAM)
-{
-#ifndef _WIN32
-    checkInterrupt();
-
-#  ifdef __FreeBSD__
-    // In case of emergency (unmount fails for some reason) not recurse into mountpoints.
-    // This prevents us from tearing up the nullfs-mounted nix store.
-    if (mountedPaths.find(path) != mountedPaths.end()) {
-        return;
-    }
-#  endif
-
-    std::string name(path.filename());
-    assert(name != "." && name != ".." && !name.empty());
-
-    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, name.c_str(), O_RDONLY | O_DIRECTORY | O_NOFOLLOW);
-        if (fd == -1)
-            throw SysError("opening directory %1%", path);
-        AutoCloseDir dir(fdopendir(fd));
-        if (!dir)
-            throw SysError("opening directory %1%", path);
-
-        struct dirent * dirent;
-        while (errno = 0, dirent = readdir(dir.get())) { /* sic */
-            checkInterrupt();
-            std::string childName = dirent->d_name;
-            if (childName == "." || childName == "..")
-                continue;
-            _deletePath(dirfd(dir.get()), path / childName, bytesFreed, ex MOUNTEDPATHS_ARG);
-        }
-        if (errno)
-            throw SysError("reading directory %1%", path);
-    }
-
-    int flags = S_ISDIR(st.st_mode) ? AT_REMOVEDIR : 0;
-    if (unlinkat(parentfd, name.c_str(), flags) == -1) {
-        if (errno == ENOENT)
-            return;
-        try {
-            throw SysError("cannot unlink %1%", path);
-        } catch (...) {
-            if (!ex)
-                ex = std::current_exception();
-            else
-                ignoreExceptionExceptInterrupt();
-        }
-    }
-#else
-    // TODO implement
-    throw UnimplementedError("_deletePath");
-#endif
-}
-
-static void _deletePath(const std::filesystem::path & path, uint64_t & bytesFreed MOUNTEDPATHS_PARAM)
-{
-    assert(path.is_absolute());
-    assert(path.parent_path() != path);
-
-    AutoCloseFD dirfd = toDescriptor(open(path.parent_path().string().c_str(), O_RDONLY));
-    if (!dirfd) {
-        if (errno == ENOENT)
-            return;
-        throw SysError("opening directory %s", path.parent_path());
-    }
-
-    std::exception_ptr ex;
-
-    _deletePath(dirfd.get(), path, bytesFreed, ex MOUNTEDPATHS_ARG);
-
-    if (ex)
-        std::rethrow_exception(ex);
-}
-
-void deletePath(const std::filesystem::path & path)
-{
-    uint64_t dummy;
-    deletePath(path, dummy);
-}
-
 void createDir(const Path & path, mode_t mode)
 {
     if (mkdir(
@@ -577,25 +441,6 @@ void createDirs(const std::filesystem::path & path)
     }
 }
 
-void deletePath(const std::filesystem::path & path, uint64_t & bytesFreed)
-{
-    // Activity act(*logger, lvlDebug, "recursively deleting path '%1%'", path);
-#ifdef __FreeBSD__
-    std::set<Path> mountedPaths;
-    struct statfs * mntbuf;
-    int count;
-    if ((count = getmntinfo(&mntbuf, MNT_WAIT)) < 0) {
-        throw SysError("getmntinfo");
-    }
-
-    for (int i = 0; i < count; i++) {
-        mountedPaths.emplace(mntbuf[i].f_mntonname);
-    }
-#endif
-    bytesFreed = 0;
-    _deletePath(path, bytesFreed MOUNTEDPATHS_ARG);
-}
-
 //////////////////////////////////////////////////////////////////////
 
 AutoDelete::AutoDelete()
@@ -672,11 +517,6 @@ void AutoUnmount::cancel()
 
 //////////////////////////////////////////////////////////////////////
 
-std::filesystem::path defaultTempDir()
-{
-    return getEnvNonEmpty("TMPDIR").value_or("/tmp");
-}
-
 std::filesystem::path createTempDir(const std::filesystem::path & tmpRoot, const std::string & prefix, mode_t mode)
 {
     while (1) {

src/libutil/include/nix/util/file-descriptor.hh

@@ -261,4 +261,14 @@ Descriptor openFileEnsureBeneathNoSymlinks(Descriptor dirFd, const CanonPath & p
 
 MakeError(EndOfFile, Error);
 
+#ifdef _WIN32
+
+/**
+ * Windows specific replacement for POSIX `lseek` that operates on a `HANDLE` and not
+ * a file descriptor.
+ */
+off_t lseek(Descriptor fd, off_t offset, int whence);
+
+#endif
+
 } // namespace nix

src/libutil/include/nix/util/file-path-impl.hh

@@ -40,6 +40,11 @@ struct UnixPathTrait
     {
         return path.rfind('/', from);
     }
+
+    static size_t rootNameLen(StringView)
+    {
+        return 0;
+    }
 };
 
 /**
@@ -83,6 +88,18 @@ struct WindowsPathTrait
         size_t p2 = path.rfind(preferredSep, from);
         return p1 == String::npos ? p2 : p2 == String::npos ? p1 : std::max(p1, p2);
     }
+
+    static size_t rootNameLen(StringView path)
+    {
+        if (path.size() >= 2 && path[1] == ':') {
+            char driveLetter = path[0];
+            if ((driveLetter >= 'A' && driveLetter <= 'Z') || (driveLetter >= 'a' && driveLetter <= 'z'))
+                return 2;
+        }
+        /* TODO: This needs to also handle UNC paths.
+         * https://learn.microsoft.com/en-us/dotnet/standard/io/file-path-formats#unc-paths */
+        return 0;
+    }
 };
 
 template<typename CharT>
@@ -116,6 +133,11 @@ typename PathDict::String canonPathInner(typename PathDict::StringView remaining
     typename PathDict::String result;
     result.reserve(256);
 
+    if (auto rootNameLength = PathDict::rootNameLen(remaining)) {
+        result += remaining.substr(0, rootNameLength); /* Copy drive letter verbatim. */
+        remaining.remove_prefix(rootNameLength);
+    }
+
     while (true) {
 
         /* Skip slashes. */

src/libutil/include/nix/util/file-system.hh

@@ -362,6 +362,8 @@ std::pair<AutoCloseFD, Path> createTempFile(const Path & prefix = "nix");
 
 /**
  * Return `TMPDIR`, or the default temporary directory if unset or empty.
+ * Uses GetTempPathW on windows which respects TMP, TEMP, USERPROFILE env variables.
+ * Does not resolve symlinks and the returned path might not be directory or exist at all.
  */
 std::filesystem::path defaultTempDir();
 

src/libutil/nar-accessor.cc

@@ -1,4 +1,5 @@
 #include "nix/util/nar-accessor.hh"
+#include "nix/util/file-descriptor.hh"
 #include "nix/util/archive.hh"
 
 #include <map>
@@ -281,7 +282,7 @@ GetNarBytes seekableGetNarBytes(const Path & path)
 GetNarBytes seekableGetNarBytes(Descriptor fd)
 {
     return [fd](uint64_t offset, uint64_t length) {
-        if (::lseek(fromDescriptorReadOnly(fd), offset, SEEK_SET) == -1)
+        if (lseek(fd, offset, SEEK_SET) == -1)
             throw SysError("seeking in file");
 
         std::string buf(length, 0);

src/libutil/serialise.cc

@@ -1,4 +1,5 @@
 #include "nix/util/serialise.hh"
+#include "nix/util/file-descriptor.hh"
 #include "nix/util/compression.hh"
 #include "nix/util/signals.hh"
 #include "nix/util/util.hh"
@@ -162,11 +163,11 @@ size_t FdSource::readUnbuffered(char * data, size_t len)
         _good = false;
         throw SysError("reading from file");
     }
+#endif
     if (n == 0) {
         _good = false;
         throw EndOfFile(std::string(*endOfFileError));
     }
-#endif
     read += n;
     return n;
 }
@@ -207,8 +208,7 @@ void FdSource::restart()
         throw Error("can't seek to the start of a file");
     buffer.reset();
     read = bufPosIn = bufPosOut = 0;
-    int fd_ = fromDescriptorReadOnly(fd);
-    if (lseek(fd_, 0, SEEK_SET) == -1)
+    if (lseek(fd, 0, SEEK_SET) == -1)
         throw SysError("seeking to the start of a file");
 }