[PATCH] D66107: [libFuzzer] Improve -merge= process to account for REDUCED corpus units.

[Max Moroz via Phabricator via llvm-commits]

Dor1s added a comment.

In D66107#1633546 <https://reviews.llvm.org/D66107#1633546>, @kcc wrote:

> I would prefer to not introduce this complexity. 
>  For periodic pruning we can use an empty dir, like you describe. 
>  For stats, we can use the overal corpus size (in bytes and in files)


Sorry, i didn't get a chance to re-write this in a better way yet.

The problem with an empty dir is that we don't have stats for the existing corpus. In order to get those, we'd need to do an extra `./fuzzer -runs=0 ...` execution for the current working corpus. And of course parse the logs yet again, calculate the difference, etc.

It is not necessary in some cases, but whenever we use corpus subset strategy or an arbitrary `-max_len` value, we do not get the correct information about the current coverage. Value profiling strategy is another trouble maker if we continue to calculate coverage on the user side.


Repository:
  rCRT Compiler Runtime

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  https://reviews.llvm.org/D66107/new/

https://reviews.llvm.org/D66107