Performance optimization in av::fixup - use buffered IO, not mapped file

Ryan Johnson
Wed Dec 12 16:02:00 GMT 2012

On 12/12/2012 4:32 AM, Corinna Vinschen wrote:
> On Dec 11 19:13, Daniel Colascione wrote:
>> On 12/11/2012 5:06 PM, Daniel Colascione wrote:
>>> On 12/10/2012 7:51 PM, Daniel Colascione wrote:
>>>> The key to generating a binary that repros the problem is to unexec emacs, then
>>>> try to repro with that generated binary, not a copy of it.
>>> The real explanation is a lot simpler: the binary is sparse. When you create a
>>> file mapping object for a sparse file, Windows discards all cached pages for
>>> that file. It makes sense that compilers (and Emacs unexec) would create sparse
>>> files as they seek around inside their outputs.
>> Anyway, the binary is sparse because our linker produces sparse files.
>> Would the Cygwin developers accept this patch?
> It's ok with me to remove this code, but there's a small problem.  On
> 2012-08-17, you wrote off-list, that you're going to send the signed
> copyright assignment form.  I never got the ok from my manager.  Did you
> miss to send the CA, or did my manager miss to inform me?
Honest question: can the deletion of someone else's code actually be 
copyrighted or claimed as IP? Or is the problem that the patch itself is 

I only wonder because---ignoring deletions---the patch changes precisely 
one line of code, which I would have thought was small enough not to 
need copyright assignment.


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