compiler: Write .o files atomically. See #14533
authorNiklas Hambüchen <mail@nh2.me>
Sun, 17 Feb 2019 19:48:45 +0000 (20:48 +0100)
committerMarge Bot <ben+marge-bot@smart-cactus.org>
Sat, 9 Mar 2019 07:14:13 +0000 (02:14 -0500)
This issue was reproduced with, and the fix confirmed with,
the `hatrace` tool for syscall-based fault injection:

    https://github.com/nh2/hatrace

The concrete test case for GHC is at

    https://github.com/nh2/hatrace/blob/e23d35a2d2c79e8bf49e9e2266b3ff7094267f29/test/HatraceSpec.hs#L185

A previous, nondeterministic reproducer for the issue was provided by
Alexey Kuleshevich in

    https://github.com/lehins/exec-kill-loop

Signed-off-by: Niklas Hambüchen <niklas@fpcomplete.com>
Reviewed-by: Alexey Kuleshevich <alexey@fpcomplete.com>
compiler/main/DriverPipeline.hs

index 04576e7..70c2d7a 100644 (file)
@@ -1339,7 +1339,12 @@ runPhase (RealPhase (As with_cpp)) input_fn dflags
                           ])
 
         liftIO $ debugTraceMsg dflags 4 (text "Running the assembler")
-        runAssembler input_fn output_fn
+
+        -- Atomic write by writing to temp file and then renaming
+        let temp_output_fn = output_fn <.> "tmp"
+        runAssembler input_fn temp_output_fn
+        liftIO $ renameFile temp_output_fn output_fn
+
         return (RealPhase next_phase, output_fn)