[PATCH] llvm-cov: Updated file checksum to be timestamp.

[Sean Silva]

On Mon, Nov 11, 2013 at 1:48 PM, Yuchen Wu <yuchenericwu at hotmail.com> wrote:

> The passes modified here are only used by llvm-cov, so they technically
> aren't part of the compiler. Is the timestamp still a problem in that case?
>

Yes. In general all tool output must be completely deterministic (a
timestamp is "nondeterministic" in the sense that it depends on the
(nondeterministic) time that the tool was built).

-- Sean Silva


>
> ----------------------------------------
> > Date: Sat, 9 Nov 2013 17:42:45 -0800
> > From: nicholas at mxc.ca
> > To: yuchenericwu at hotmail.com
> > CC: llvm-commits at cs.uiuc.edu
> > Subject: Re: [PATCH] llvm-cov: Updated file checksum to be timestamp.
> >
> > Yuchen Wu wrote:
> >> llvm-cov: Updated file checksum to be timestamp.
> >>
> >> Instead of permanently outputting "MVLL" as the file checksum, clang
> >> will stamp the gcno and gcda checksums with the time of compile.
> >
> > Absolutely not. The compiler must generate identical outputs when it is
> > run twice. Please find another way to pick a checksum.
> >
> > Nick
> >
> > This
> >> allows for llvm-cov to check if the two gcov files are synchronized.
> >>
> >> Regenerated the test files so they contain the timestamp. Also added
> >> negative test to ensure error when the checksums don't match.
> >>
> >>
> >>
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> >
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