Drop guessOrInventPathFromFD()

No need to do hacky stuff like that when we already know the original path.

src/libstore/unix/build/derivation-builder.cc

@@ -314,7 +314,7 @@ protected:
     /**
      * Make a file owned by the builder addressed by its file descriptor.
      */
-    void chownToBuilder(const AutoCloseFD & fd);
+    void chownToBuilder(int fd, const Path & path);
 
     /**
      * Run the builder's process.
@@ -730,7 +730,7 @@ void DerivationBuilderImpl::startBuilder()
     if (!tmpDirFd)
         throw SysError("failed to open the build temporary directory descriptor '%1%'", tmpDir);
 
-    chownToBuilder(tmpDirFd);
+    chownToBuilder(tmpDirFd.get(), tmpDir);
 
     for (auto & [outputName, status] : initialOutputs) {
         /* Set scratch path we'll actually use during the build.
@@ -1073,8 +1073,8 @@ void DerivationBuilderImpl::initEnv()
                 AutoCloseFD passAsFileFd{openat(tmpDirFd.get(), fn.c_str(), O_WRONLY | O_TRUNC | O_CREAT | O_CLOEXEC | O_EXCL | O_NOFOLLOW, 0666)};
                 if (!passAsFileFd)
                     throw SysError("opening `passAsFile` file in the sandbox '%1%'", p);
-                writeFile(passAsFileFd, rewriteStrings(i.second, inputRewrites));
-                chownToBuilder(passAsFileFd);
+                writeFile(passAsFileFd, p, rewriteStrings(i.second, inputRewrites));
+                chownToBuilder(passAsFileFd.get(), p);
                 env[i.first + "Path"] = tmpDirInSandbox() + "/" + fn;
             }
         }
@@ -1278,11 +1278,11 @@ void DerivationBuilderImpl::chownToBuilder(const Path & path)
         throw SysError("cannot change ownership of '%1%'", path);
 }
 
-void DerivationBuilderImpl::chownToBuilder(const AutoCloseFD & fd)
+void DerivationBuilderImpl::chownToBuilder(int fd, const Path & path)
 {
     if (!buildUser) return;
-    if (fchown(fd.get(), buildUser->getUID(), buildUser->getGID()) == -1)
-        throw SysError("cannot change ownership of file '%1%'", fd.guessOrInventPath());
+    if (fchown(fd, buildUser->getUID(), buildUser->getGID()) == -1)
+        throw SysError("cannot change ownership of file '%1%'", path);
 }
 
 void DerivationBuilderImpl::runChild()

src/libutil/file-descriptor.cc

@@ -1,8 +1,5 @@
 #include "nix/util/serialise.hh"
 #include "nix/util/util.hh"
-#include "nix/util/file-system.hh"
-
-#include "util-config-private.hh"
 
 #include <fcntl.h>
 #include <unistd.h>
@@ -77,29 +74,6 @@ Descriptor AutoCloseFD::get() const
     return fd;
 }
 
-std::string guessOrInventPathFromFD(Descriptor fd)
- {
-     assert(fd >= 0);
-     /* On Linux, there's no F_GETPATH available.
-      * But we can read /proc/ */
- #if defined(__linux__)
-     try {
-         return readLink(fmt("/proc/self/fd/%1%", fd));
-     } catch (...) {
-     }
- #elif defined (HAVE_F_GETPATH) && HAVE_F_GETPATH
-     std::string fdName(PATH_MAX, '\0');
-     if (fcntl(fd, F_GETPATH, fdName.data()) != -1) {
-         fdName.resize(strlen(fdName.c_str()));
-         return fdName;
-     }
- #else
- #error "No implementation for retrieving file descriptors path."
- #endif
-
-     return fmt("<fd %i>", fd);
- }
-
 
 void AutoCloseFD::close()
 {

src/libutil/file-system.cc

@@ -315,19 +315,19 @@ void writeFile(const Path & path, std::string_view s, mode_t mode)
     if (!fd)
         throw SysError("opening file '%1%'", path);
 
-    writeFile(fd, s, mode);
+    writeFile(fd, path, s, mode);
 
     /* Close explicitly to propagate the exceptions. */
     fd.close();
 }
 
-void writeFile(AutoCloseFD & fd, std::string_view s, mode_t mode)
+void writeFile(AutoCloseFD & fd, const Path & origPath, std::string_view s, mode_t mode)
 {
     assert(fd);
     try {
         writeFull(fd.get(), s);
     } catch (Error & e) {
-        e.addTrace({}, "writing file '%1%'", fd.guessOrInventPath());
+        e.addTrace({}, "writing file '%1%'", origPath);
         throw;
     }
 }
@@ -339,7 +339,7 @@ void writeFileAndSync(const Path & path, std::string_view s, mode_t mode)
         if (!fd)
             throw SysError("opening file '%1%'", path);
 
-        writeFile(fd, s, mode);
+        writeFile(fd, path, s, mode);
         fd.fsync();
         /* Close explicitly to ensure that exceptions are propagated. */
         fd.close();
@@ -444,8 +444,6 @@ 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
-    /* This ensures that `name` is an immediate child of `parentfd`. */
-    assert(!path.empty() && path.string().find('/') == std::string::npos && "`name` is an immediate child to `parentfd`");
     checkInterrupt();
 
 #ifdef __FreeBSD__
@@ -456,13 +454,14 @@ static void _deletePath(Descriptor parentfd, const std::filesystem::path & path,
     }
 #endif
 
-    std::string name(path.native());
+    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%' in directory '%2%'", name, guessOrInventPathFromFD(parentfd));
+        throw SysError("getting status of %1%", path);
     }
 
     if (!S_ISDIR(st.st_mode)) {
@@ -493,24 +492,23 @@ static void _deletePath(Descriptor parentfd, const std::filesystem::path & path,
         /* 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%' in directory '%2%'", name, guessOrInventPathFromFD(parentfd));
-            }
+            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%' in directory '%2%'", name, guessOrInventPathFromFD(parentfd));
+            throw SysError("opening directory %1%", path);
         AutoCloseDir dir(fdopendir(fd));
         if (!dir)
-            throw SysError("opening directory '%1%' in directory '%2%'", name, guessOrInventPathFromFD(parentfd));
+            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()), childName, bytesFreed, ex MOUNTEDPATHS_ARG);
+            _deletePath(dirfd(dir.get()), path / childName, bytesFreed, ex MOUNTEDPATHS_ARG);
         }
         if (errno) throw SysError("reading directory %1%", path);
     }
@@ -519,7 +517,7 @@ static void _deletePath(Descriptor parentfd, const std::filesystem::path & path,
     if (unlinkat(parentfd, name.c_str(), flags) == -1) {
         if (errno == ENOENT) return;
         try {
-            throw SysError("cannot unlink '%1%' in directory '%2%'", name, guessOrInventPathFromFD(parentfd));
+            throw SysError("cannot unlink %1%", path);
         } catch (...) {
             if (!ex)
                 ex = std::current_exception();
@@ -535,19 +533,18 @@ static void _deletePath(Descriptor parentfd, const std::filesystem::path & path,
 
 static void _deletePath(const std::filesystem::path & path, uint64_t & bytesFreed MOUNTEDPATHS_PARAM)
 {
-    Path dir = dirOf(path.string());
-    if (dir == "")
-        dir = "/";
+    assert(path.is_absolute());
+    assert(path.parent_path() != path);
 
-    AutoCloseFD dirfd = toDescriptor(open(dir.c_str(), O_RDONLY));
+    AutoCloseFD dirfd = toDescriptor(open(path.parent_path().string().c_str(), O_RDONLY));
     if (!dirfd) {
         if (errno == ENOENT) return;
-        throw SysError("opening directory '%1%'", path);
+        throw SysError("opening directory %s", path.parent_path());
     }
 
     std::exception_ptr ex;
 
-    _deletePath(dirfd.get(), path.filename(), bytesFreed, ex MOUNTEDPATHS_ARG);
+    _deletePath(dirfd.get(), path, bytesFreed, ex MOUNTEDPATHS_ARG);
 
     if (ex)
         std::rethrow_exception(ex);

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

@@ -106,14 +106,6 @@ void drainFD(
 #endif
     );
 
- /*
-  * Will attempt to guess *A* path associated that might lead to the same file as used by this
-  * file descriptor.
-  *
-  * The returned string should NEVER be used as a valid path.
-  */
- std::string guessOrInventPathFromFD(Descriptor fd);
-
 /**
  * Get [Standard Input](https://en.wikipedia.org/wiki/Standard_streams#Standard_input_(stdin))
  */
@@ -168,15 +160,6 @@ public:
     AutoCloseFD& operator =(const AutoCloseFD & fd) = delete;
     AutoCloseFD& operator =(AutoCloseFD&& fd);
     Descriptor get() const;
-
-    /**
-     * Will attempt to guess *A* path associated that might lead to the same file as used by this
-     * file descriptor.
-     *
-     * The returned string should NEVER be used as a valid path.
-     */
-    std::string guessOrInventPath() const { return guessOrInventPathFromFD(fd); }
-
     explicit operator bool() const;
     Descriptor release();
     void close();

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

@@ -173,18 +173,20 @@ void readFile(const Path & path, Sink & sink, bool memory_map = true);
  * Write a string to a file.
  */
 void writeFile(const Path & path, std::string_view s, mode_t mode = 0666);
+
 static inline void writeFile(const std::filesystem::path & path, std::string_view s, mode_t mode = 0666)
 {
     return writeFile(path.string(), s, mode);
 }
 
 void writeFile(const Path & path, Source & source, mode_t mode = 0666, bool sync = false);
+
 static inline void writeFile(const std::filesystem::path & path, Source & source, mode_t mode = 0666, bool sync = false)
 {
     return writeFile(path.string(), source, mode, sync);
 }
 
-void writeFile(AutoCloseFD & fd, std::string_view s, mode_t mode = 0666 );
+void writeFile(AutoCloseFD & fd, const Path & origPath, std::string_view s, mode_t mode = 0666);
 
 /**
  * Write a string to a file and flush the file and its parents direcotry to disk.

src/libutil/meson.build

@@ -37,8 +37,6 @@ foreach funcspec : check_funcs
   configdata.set(define_name, define_value, description: funcspec[1])
 endforeach
 
-configdata.set('HAVE_F_GETPATH', cxx.has_header_symbol('fcntl.h', 'F_GETPATH').to_int())
-
 subdir('nix-meson-build-support/libatomic')
 
 if host_machine.system() == 'windows'