stjordanis / fasm

F# -> ASM disassembler

fasm

A F# to Jitted ASM / IL disassembler as a dotnet tool

Getting Started

Install fasm as a global dotnet tool

dotnet tool install fasm -g

or as a dotnet local tool

dotnet new tool-manifest
dotnet tool install fasm

Quickstart

Create a demo.fsx F# interactive script:

let inc x = x+1

run fasm:

dotnet fasm ./demo.fsx

and open at the generated demo.asm file:

Demo.inc(Int32)
L0000: lea eax, [rcx+1]
L0003: ret

Watch mode

run fasm in watch mode:

dotnet fasm ./demo.fsx -w

Open the demo.fsx and demo.asm files side by side in your favorite editor, make changes to demo.fsx and save. The demo.asm file is updated on the fly.

Usage

USAGE: dotnet fasm [--help] [--console] [--output <string>] [--watch] [--platform <x86|x64>] [--language <asm|il>] <string>

SOURCE:

    <string>              the source fsx or dotnet assembly file

OPTIONS:

    --console, -c         output to console
    --output, -o <string> specifiy the output file
    --watch, -w           run in watch mode
    --platform, -p <x86|x64>
                          specify the platform for disassembly
    --language, -l <asm|il>
                          specify the output language (asm/il)
    --help                display this list of options.

Input

The input can be a fsx F# script file or any dotnet .dll assemlby file. F# scripts are compiled for net 5.0.

Using a dotnet assembly as an input, you can use fasm on any dotnet language.

Console

With the -c flag, the result is output to console rather than in a file.

Output

Use the -o flag to specifie the target file path and name.

Watch

The -w flags runs fasm in watch mode. The file is recompiled and disassembled automatically when saved.

Platform

Use the -p flag to force x64 or x86 platform for disassembly.

Language

Specify the target language with the -l flag:

• asm : disassemble the jit output as a x86/x86 .asm file
• il : disassemble the output as a MSIL .il file

Acknowledgment

This tool is based on Andrey Shchekin code for https://sharplab.io/.

Contributing

Help and feedback is always welcome and pull requests get accepted.

• First open an issue to discuss your changes
• After your change has been formally approved please submit your PR against the develop branch
• Please follow the code convention by examining existing code
• Add/modify the README.md as required
• Add/modify unit tests as required
• Please document your changes in the upcoming release notes in RELEASE_NOTES.md
• PRs can only be approved and merged when all checks succeed (builds on Windows, MacOs and Linux)

License

MIT