How do I install the Decomp Permuter skill?

Run npx skillmds add majiayu000/decomp-permuter-2 in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Decomp Permuter safe to use?

This skill has not completed SkillMD's automated safety review yet. Capability flags: docs only. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Decomp Permuter?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Decomp Permuter free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Decomp Permuter?

majiayu000 (@majiayu000) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Decomp Permuter by majiayu000 — Agent Skill

Name: Decomp Permuter
Rating: 4.2 (5 reviews)
Author: majiayu000

Decomp Permuter

Decomp-Permuter is a tool that automatically permutes C files to better match a target binary. Use this skill when you are decompiling a function and it is almost matching except for some register differences (i.e. 95%+). Or if you are otherwise unable to make progress on a function decompilation. Do not use it when there are control flow or functional differences; it's often easy to resolve those by hand, and neither the scorer nor the randomizer tends to play well with them.

majiayu000 044efb2 2 files · 2.8 KB Updated Sep 9, 2026 567 repo stars

File contents

Permute a Function

Instructions

These instructions assume you are in the root directory of the Github repo.

Step 1: Run the permuter

Run the permuter with the --source-file (or -s) flag pointing to your best matching attempt:

timeout 300s ./tools/permuter --source-file nonmatchings/<function-name>/base_N.c <function name>

This will automatically create a permuter environment and run the permuter for 300 seconds. You can tweak this number to an appropriate time. If you fail to use the timeout command the permuter will run forever.

Requirements for source file:

Must compile successfully
Should already be 95%+ match (permuter works on register allocation, not control flow)
Only one function body should be implemented (extern declarations for other functions are fine)
Include all necessary headers at the top

The permuter will report match improvements. These will be located in nonmatchings/function-name-<optional number>/output-<score>-<optional number>. The full C code will be in source.c. A diff.txt file is also available with the changes the permuter made.

Iterating on a Permuted Function

Look at the changes outputted by the permuter and use them to improve your own C code. Do not attempt to iterate directly on the base.c file. Create a new version of the function (e.g., base_N+1.c) and re-run the permuter with --source-file pointing to the new file.

Beware of permuter artefacts and noise

The permuter is dangerous. It can lead you to local optima. Only incorporate decomp-permuter changes that make logical sense within the context of the function you are matching.

For example, decomp-permuter may tell you to move or delete a line or statement that you know is necessary for the function to make logical sense. This may temporarily bump the match percentage but cannot ever be a path to 100% match.

---name: decomp-permuter-2description: Decomp-Permuter is a tool that automatically permutes C files to better match a target binary. Use this skill when you are decompiling a function and it is almost matching except for some register differences (i.e. 95%+). Or if you are otherwise unable to make progress on a function decompilation. Do not use it when there are control flow or functional differences; it's often easy to resolve those by hand, and neither the scorer nor the randomizer tends to play well with them.--- # Permute a Function ## Instructions These instructions assume you are in the root directory of the Github repo. ### Step 1: Run the permuter Run the permuter with the `--source-file` (or `-s`) flag pointing to your best matching attempt: ```bash timeout 300s ./tools/permuter --source-file nonmatchings/<function-name>/base_N.c <function name> ``` This will automatically create a permuter environment and run the permuter for 300 seconds. You can tweak this number to an appropriate time. If you fail to use the `timeout` command the permuter will run forever. **Requirements for source file:** - Must compile successfully - Should already be 95%+ match (permuter works on register allocation, not control flow) - Only one function body should be implemented (extern declarations for other functions are fine) - Include all necessary headers at the top The permuter will report match improvements. These will be located in `nonmatchings/function-name-<optional number>/output-<score>-<optional number>`. The full C code will be in `source.c`. A `diff.txt` file is also available with the changes the permuter made. ## Iterating on a Permuted Function Look at the changes outputted by the permuter and use them to improve your own C code. Do not attempt to iterate directly on the base.c file. Create a new version of the function (e.g., base_N+1.c) and re-run the permuter with `--source-file` pointing to the new file. ### Beware of permuter artefacts and noise The permuter is dangerous. It can lead you to local optima. Only incorporate decomp-permuter changes that make logical sense within the context of the function you are matching. For example, decomp-permuter may tell you to move or delete a line or statement that you know is necessary for the function to make logical sense. This may temporarily bump the match percentage but cannot ever be a path to 100% match.

Frequently asked questions