[llvm] r314345 - Do not remove a target file in FileOutputBuffer::create().

[Rafael Avila de Espindola via llvm-commits]

Thanks!

Rui Ueyama via llvm-commits <llvm-commits at lists.llvm.org> writes:

> Author: ruiu
> Date: Wed Sep 27 14:19:24 2017
> New Revision: 314345
>
> URL: http://llvm.org/viewvc/llvm-project?rev=314345&view=rev
> Log:
> Do not remove a target file in FileOutputBuffer::create().
>
> FileOutputBuffer::create() attempts to remove a target file if the file
> is a regular one, which results in an unexpected result in a failure
> scenario.
>
> If something goes wrong and the user of FileOutputBuffer decides to not
> call commit(), it leaves nothing. An existing file is removed, and no
> new file is created.
>
> What we should do is to atomically replace an existing file with a new
> file using rename(), so that it wouldn't remove an existing file without
> creating a new one.
>
> Differential Revision: https://reviews.llvm.org/D38283
>
> Modified:
>     llvm/trunk/lib/Support/FileOutputBuffer.cpp
>
> Modified: llvm/trunk/lib/Support/FileOutputBuffer.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/FileOutputBuffer.cpp?rev=314345&r1=314344&r2=314345&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Support/FileOutputBuffer.cpp (original)
> +++ llvm/trunk/lib/Support/FileOutputBuffer.cpp Wed Sep 27 14:19:24 2017
> @@ -65,13 +65,6 @@ FileOutputBuffer::create(StringRef FileP
>        IsRegular = false;
>    }
>  
> -  if (IsRegular) {
> -    // Delete target file.
> -    EC = sys::fs::remove(FilePath);
> -    if (EC)
> -      return EC;
> -  }
> -
>    SmallString<128> TempFilePath;
>    int FD;
>    if (IsRegular) {
> @@ -125,7 +118,7 @@ std::error_code FileOutputBuffer::commit
>  
>    std::error_code EC;
>    if (IsRegular) {
> -    // Rename file to final name.
> +    // Atomically replace the existing file with the new one.
>      EC = sys::fs::rename(Twine(TempPath), Twine(FinalPath));
>      sys::DontRemoveFileOnSignal(TempPath);
>    } else {
>
>
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