docs(aflpp): add opinionated environment variables guide#130
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GrosQuildu merged 3 commits intotrailofbits:mainfrom Mar 27, 2026
Merged
docs(aflpp): add opinionated environment variables guide#130GrosQuildu merged 3 commits intotrailofbits:mainfrom
GrosQuildu merged 3 commits intotrailofbits:mainfrom
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GrosQuildu
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Mar 23, 2026
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Thanks a lot! Some comments from me:
AFL_FAST_CAL - docs says to use it for slow targets
AFL_FINAL_SYNC - this is only important for cmin, unless I miss something? Current description sounds like the fuzzing itself could be harmed when this envvar is missing
AFL_TESTCACHE_SIZE - I would mention that default is 50 MB and the "good values" are in range 50-250
AFL_NO_ARITH - docs mention it may be useful for fuzzing test-based formats. Sounds about right, we shouldn't discourage people from using it without a note.
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Thanks for the thorough review @GrosQuildu! All points addressed:
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Friendly ping — this PR is ready for review. Happy to make any changes needed. 🙏 |
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Thanks for the review, @GrosQuildu! I've pushed a fix addressing all four points:
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Thanks |
Add a practical "Environment Variables That Matter" section covering: - Always-set variables (AFL_TMPDIR, AFL_FAST_CAL) for free perf wins - Multi-core campaign variables (AFL_FINAL_SYNC, AFL_TESTCACHE_SIZE) - CI/automated fuzzing variables (AFL_EXIT_ON_TIME, AFL_NO_UI) - Variables to avoid (AFL_NO_ARITH, AFL_SHUFFLE_QUEUE, AFL_DISABLE_TRIM) Follow-up from PR trailofbits#15 review feedback. Closes trailofbits#18
- AFL_FAST_CAL: clarify it's recommended for slow targets, not universal - AFL_FINAL_SYNC: correct scope to afl-cmin corpus minimization - AFL_TESTCACHE_SIZE: add default (50 MB) and recommended range (50-250) - AFL_NO_ARITH: note it may help for text-based formats
- AFL_FAST_CAL: move to its own "Slow Targets" section to clarify it's specifically recommended for slow targets, not always - AFL_FINAL_SYNC: clarify it only matters for afl-cmin corpus minimization, not for the fuzzing process itself - AFL_TESTCACHE_SIZE: mention default is 50 MB and good range is 50-250 MB - AFL_NO_ARITH: soften wording to note it may be useful for text-based targets Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>
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Summary
Closes #18
Adds a practical "Environment Variables That Matter" section to the AFL++ skill, based on real-world fuzzing experience. Rather than duplicating the official docs, this provides opinionated guidance on which variables to use and why.
Sections Added
AFL_TMPDIR,AFL_FAST_CALAFL_FINAL_SYNC,AFL_TESTCACHE_SIZEAFL_EXIT_ON_TIME,AFL_EXIT_WHEN_DONE,AFL_NO_UIAFL_NO_ARITH,AFL_SHUFFLE_QUEUE,AFL_DISABLE_TRIMPlacement
Inserted between "Running Campaigns" and "Multi-Core Fuzzing" sections — after the user knows how to run AFL++ but before they scale up.
Follow-up from PR #15 review feedback.