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Langston Barrett 2023-03-16 16:56:35 -04:00 committed by Michael Goulet
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src/fuzzing.md
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@ -26,9 +26,10 @@ project, please read this guide before reporting fuzzer-generated bugs!
*Please don't:*
- Report lots of bugs that use internal features, including but not limited to
`custom_mir`, `lang_items`, `no_core`, and `rustc_attrs`.
- Seed your fuzzer with inputs that are known to crash rustc (details below).
- Don't report lots of bugs that use internal features, including but not
limited to `custom_mir`, `lang_items`, `no_core`, and `rustc_attrs`.
- Don't seed your fuzzer with inputs that are known to crash rustc (details
below).
### Discussion
@ -107,16 +108,17 @@ these tools, post both the complete and minimized test cases. Generally,
## Effective fuzzing
When fuzzing rustc, you may want to avoid generating code, since this is mostly
done by LLVM. Try `--emit=mir` instead.
When fuzzing rustc, you may want to avoid generating machine code, since this
is mostly done by LLVM. Try `--emit=mir` instead.
A variety of compiler flags can uncover different issues. `-Zmir-opt-level=4`
will turn on MIR optimization passes that are not run by default, potentially
uncovering interesting bugs.
uncovering interesting bugs. `-Zvalidate-mir` can help uncover such bugs.
If you're fuzzing a compiler you built, you may want to build it with `-C
target-cpu=native` or even PGO/BOLT to squeeze out a few more executions per
second.
second. Of course, it's best to try multiple build configurations and see
what actually results in superior throughput.
## Existing projects