opt-level = 3?

[emk]

By adding the following to fuzz/Cargo.toml:

+[profile.dev]
+opt-level = 3

…I improve fuzzer throughput from:

#524288 pulse  cov: 3738 corp: 80/10238b exec/s: 1420 rss: 574Mb

...to:

#1048576    pulse  cov: 1584 corp: 79/10254b exec/s: 6808 rss: 594Mb

What would the tradeoffs be for including this in the default Cargo.toml, or at least documenting it?

[emk]

Also note that coverage numbers drop drastically, probably because of the elimination of basic blocks by the optimizer. But the corpus remains the same size.

[whitequark]

This may not necessarily be desirable because building unsafe code with opt-level = 0 is likely to leave more (most, though not all) dynamically reachable UB as it is. But it should be fine with safe code only; so a commented-by-default line with an explanation in Cargo.toml would be harmless and instructive.

[whitequark]

Or perhaps we could leave profiles alone and just mention the cargo fuzz run foo --release invocation in README. Though it ought to be obvious to anyone with even little Rust experience.

[nagisa]

IIRC this issue predates the --release flag.