[llvm-commits] [llvm] r82434 - /llvm/trunk/include/llvm/Support/FormattedStream.h

Dan Gohman gohman at apple.com
Mon Sep 21 18:21:04 CDT 2009


Hi Daniel,

With this change, errs() is now becoming buffered, which is
very inconvenient.

Dan

On Sep 20, 2009, at 8:56 PM, Daniel Dunbar wrote:

> Author: ddunbar
> Date: Sun Sep 20 22:56:00 2009
> New Revision: 82434
>
> URL: http://llvm.org/viewvc/llvm-project?rev=82434&view=rev
> Log:
> Don't allow formatted_ostream to be unbuffered, even if its  
> underlying buffer
> is.
> - The problem is that formatted_ostream forces its underlying buffer  
> to be
>   unbuffered, so if some client happens to wrap a formatted_ostream  
> around
>   something, but still use the underlying stream, then we can end up  
> writing on
>   a fully unbuffered output (which was never intended to be  
> unbuffered).
>
> - This makes clang (and presumably llvm-gcc) -emit-llvm -S a mere  
> 10x faster.
>
> Modified:
>    llvm/trunk/include/llvm/Support/FormattedStream.h
>
> Modified: llvm/trunk/include/llvm/Support/FormattedStream.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/FormattedStream.h?rev=82434&r1=82433&r2=82434&view=diff
>
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> ======================================================================
> --- llvm/trunk/include/llvm/Support/FormattedStream.h (original)
> +++ llvm/trunk/include/llvm/Support/FormattedStream.h Sun Sep 20  
> 22:56:00 2009
> @@ -105,10 +105,15 @@
>       // own buffering, and it doesn't need or want TheStream to do  
> another
>       // layer of buffering underneath. Resize the buffer to what  
> TheStream
>       // had been using, and tell TheStream not to do its own  
> buffering.
> +      //
> +      // If the underlying stream is unbuffered, just use its  
> preferred buffer
> +      // size. We can't treat this as an honest wish for unbuffered  
> output,
> +      // because it could very well be a stream we previously  
> forced to be
> +      // unbuffered.
>       if (size_t BufferSize = TheStream->GetBufferSize())
>         SetBufferSize(BufferSize);
>       else
> -        SetUnbuffered();
> +        SetBuffered();
>       TheStream->SetUnbuffered();
>
>       Scanned = 0;
>
>
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