diff options
Diffstat (limited to 'compiler/utils/Util.hs')
| -rw-r--r-- | compiler/utils/Util.hs | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/compiler/utils/Util.hs b/compiler/utils/Util.hs index 16864fe017..41f63f2246 100644 --- a/compiler/utils/Util.hs +++ b/compiler/utils/Util.hs @@ -99,6 +99,7 @@ module Util ( doesDirNameExist, getModificationUTCTime, modificationTimeIfExists, + withAtomicRename, global, consIORef, globalM, sharedGlobal, sharedGlobalM, @@ -145,9 +146,10 @@ import GHC.Stack (HasCallStack) import Control.Applicative ( liftA2 ) import Control.Monad ( liftM, guard ) +import Control.Monad.IO.Class ( MonadIO, liftIO ) import GHC.Conc.Sync ( sharedCAF ) import System.IO.Error as IO ( isDoesNotExistError ) -import System.Directory ( doesDirectoryExist, getModificationTime ) +import System.Directory ( doesDirectoryExist, getModificationTime, renameFile ) import System.FilePath import Data.Char ( isUpper, isAlphaNum, isSpace, chr, ord, isDigit, toUpper @@ -1304,6 +1306,26 @@ modificationTimeIfExists f = do else ioError e -- -------------------------------------------------------------- +-- atomic file writing by writing to a temporary file first (see #14533) +-- +-- This should be used in all cases where GHC writes files to disk +-- and uses their modification time to skip work later, +-- as otherwise a partially written file (e.g. due to crash or Ctrl+C) +-- also results in a skip. + +withAtomicRename :: (MonadIO m) => FilePath -> (FilePath -> m a) -> m a +withAtomicRename targetFile f = do + -- The temp file must be on the same file system (mount) as the target file + -- to result in an atomic move on most platforms. + -- The standard way to ensure that is to place it into the same directory. + -- This can still be fooled when somebody mounts a different file system + -- at just the right time, but that is not a case we aim to cover here. + let temp = targetFile <.> "tmp" + res <- f temp + liftIO $ renameFile temp targetFile + return res + +-- -------------------------------------------------------------- -- split a string at the last character where 'pred' is True, -- returning a pair of strings. The first component holds the string -- up (but not including) the last character for which 'pred' returned |