[Support] NFC: Allow modifying access/modification times independently in sys::fs::setLastModificationAndAccessTime.

[rupprecht]

Summary

Add an overload to sys::fs::setLastModificationAndAccessTime that allows setting last access and modification times separately. This will allow tools to use this API when they want to preserve both the access and modification times from an input file, which may be different.

Also note that both the POSIX (futimens/futimes) and Windows (SetFileTime) APIs take the two timestamps in the order of (1) access (2) modification time, so this renames the method to "setLastAccessAndModificationTime" to make it clear which timestamp is which.

For existing callers, the 1-arg overload just sets both timestamps to the same thing.

include/llvm/Support/FileSystem.h

inline std::error_code file_size(const Twine &Path, uint64_t &Result) {
   return std::error_code();
 }
 
 /// Set the file modification and access time.
 ///
 /// @returns errc::success if the file times were successfully set, otherwise a
 ///          platform-specific error_code or errc::function_not_supported on
 ///          platforms where the functionality isn't available.
-std::error_code setLastModificationAndAccessTime(int FD, TimePoint<> Time);
+std::error_code setLastAccessAndModificationTime(int FD, TimePoint<> AccessTime,
+                                                 TimePoint<> ModificationTime);
+
+/// Simpler version that sets both file modification and access time to the same
+/// time.
+inline std::error_code setLastAccessAndModificationTime(int FD,
+                                                        TimePoint<> Time) {
+  return setLastAccessAndModificationTime(FD, Time, Time);
+}
 
 /// Is status available?
 ///
 /// @param s Input file status.
 /// @returns True if status() != status_error.
 bool status_known(const basic_file_status &s);
 
 /// Is status available?

lib/Support/Unix/Path.inc

std::error_code setPermissions(const Twine &Path, perms Permissions) {
   SmallString<128> PathStorage;
   StringRef P = Path.toNullTerminatedStringRef(PathStorage);
 
   if (::chmod(P.begin(), Permissions))
     return std::error_code(errno, std::generic_category());
   return std::error_code();
 }
 
-std::error_code setLastModificationAndAccessTime(int FD, TimePoint<> Time) {
+std::error_code setLastAccessAndModificationTime(int FD, TimePoint<> AccessTime,
+                                                 TimePoint<> ModificationTime) {
 #if defined(HAVE_FUTIMENS)
   timespec Times[2];
-  Times[0] = Times[1] = sys::toTimeSpec(Time);
+  Times[0] = sys::toTimeSpec(AccessTime);
+  Times[1] = sys::toTimeSpec(ModificationTime);
   if (::futimens(FD, Times))
     return std::error_code(errno, std::generic_category());
   return std::error_code();
 #elif defined(HAVE_FUTIMES)
   timeval Times[2];
-  Times[0] = Times[1] = sys::toTimeVal(
-      std::chrono::time_point_cast<std::chrono::microseconds>(Time));
+  Times[0] = sys::toTimeVal(
+      std::chrono::time_point_cast<std::chrono::microseconds>(AccessTime));
+  Times[1] =
+      sys::toTimeVal(std::chrono::time_point_cast<std::chrono::microseconds>(
+          ModificationTime));
   if (::futimes(FD, Times))
     return std::error_code(errno, std::generic_category());
   return std::error_code();
 #else
 #warning Missing futimes() and futimens()
   return make_error_code(errc::function_not_supported);
 #endif
 }

lib/Support/Windows/Path.inc

std::error_code setPermissions(const Twine &Path, perms Permissions) {
   }
 
   if (!::SetFileAttributesW(PathUTF16.begin(), Attributes))
     return mapWindowsError(GetLastError());
 
   return std::error_code();
 }
 
-std::error_code setLastModificationAndAccessTime(int FD, TimePoint<> Time) {
-  FILETIME FT = toFILETIME(Time);
+std::error_code setLastAccessAndModificationTime(int FD, TimePoint<> AccessTime,
+                                                 TimePoint<> ModificationTime) {
+  FILETIME AccessFT = toFILETIME(AccessTime);
+  FILETIME ModifyFT = toFILETIME(ModificationTime);
   HANDLE FileHandle = reinterpret_cast<HANDLE>(_get_osfhandle(FD));
-  if (!SetFileTime(FileHandle, NULL, &FT, &FT))
+  if (!SetFileTime(FileHandle, NULL, &AccessFT, &ModifyFT))
     return mapWindowsError(::GetLastError());
   return std::error_code();
 }
 
 std::error_code mapped_file_region::init(int FD, uint64_t Offset,
                                          mapmode Mode) {
   this->Mode = Mode;
   HANDLE OrigFileHandle = reinterpret_cast<HANDLE>(_get_osfhandle(FD));

tools/llvm-ar/llvm-ar.cpp

static void doExtract(StringRef Name, const object::Archive::Child &C) {
   }
 
   // If we're supposed to retain the original modification times, etc. do so
   // now.
   if (OriginalDates) {
     auto ModTimeOrErr = C.getLastModified();
     failIfError(ModTimeOrErr.takeError());
     failIfError(
-        sys::fs::setLastModificationAndAccessTime(FD, ModTimeOrErr.get()));
+        sys::fs::setLastAccessAndModificationTime(FD, ModTimeOrErr.get()));
   }
 
   if (close(FD))
     fail("Could not close the file");
 }
 
 static bool shouldCreateArchive(ArchiveOperation Op) {
   switch (Op) {

unittests/Support/Path.cpp

#ifdef _WIN32
   // https://blogs.technet.microsoft.com/filecab/2006/11/07/disabling-last-access-time-in-windows-vista-to-improve-ntfs-performance/
   // This part of the unit test is Windows specific as the updating of
   // access times can be disabled on Linux using /etc/fstab.
 
   // Set access time to UNIX epoch.
   ASSERT_NO_ERROR(sys::fs::openFileForWrite(Twine(TempPath), FileDescriptor,
                                             fs::CD_OpenExisting));
   TimePoint<> Epoch(std::chrono::milliseconds(0));
-  ASSERT_NO_ERROR(fs::setLastModificationAndAccessTime(FileDescriptor, Epoch));
+  ASSERT_NO_ERROR(fs::setLastAccessAndModificationTime(FileDescriptor, Epoch));
   ::close(FileDescriptor);
 
   // Open the file and ensure access time is updated, when forced.
   ASSERT_NO_ERROR(fs::openFileForRead(Twine(TempPath), FileDescriptor,
                                       fs::OF_UpdateAtime, &ResultPath));
 
   sys::fs::file_status Status;
   ASSERT_NO_ERROR(sys::fs::status(FileDescriptor, Status));