libMultiMarkdown7 7.0.0-alpha.1
Lightweight markup processor to produce HTML, LaTeX, and more.
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libMultiMarkdown7

Title: libMultiMarkdown7
Author: Fletcher T. Penney
Date: 2025-09-08
Copyright: Copyright © 2024-2025 Fletcher T. Penney.
Version: 7.0.0-alpha.1

MultiMarkdown 7.0.0-alpha.1

Lightweight markup processor to produce HTML, LaTeX, and more.

About

Why a new version of MultiMarkdown? Briefly, I wanted to:

  • Improve performance – MMD v6 was a big improvement over prior versions, but time goes on and performance was no longer "up to snuff"
  • Clean up the code – v6 was a (almost) complete rewrite from v5, and there was a lot of "learning while building" during development that lead to sloppy code in some places
  • Improve the API – the v6 API made sense to me at the time during development, but didn't really fit with the way MMD would be called as a library
  • Simplify – simple code is almost always easier to maintain and offers better performance.... There was a lot of room to simplify!
  • Improve the syntax and output – during development and testing I was able to continue to make small fixes to various edge cases. But generally the syntax for MultiMarkdown 7 is the same as MultiMarkdown 6.

Current Status (2025-09-10)

  • HTML support should be complete. I've had to update the HTML test suite from v6, but all of the tests are passed. This should represent intentional changes to the HTML output, but some inadvertent changes may have snuck through. I will add support for other formats as time goes on and as I become more confident that the core engine is complete and correct.
  • HTML compatibility mode passes the test suite. Compatibility mode turns off functionality that is not part of the core Markdown syntax (e.g. footnotes, citations, fenced code blocks, etc.).
  • LaTeX support should be complete. The intent is that changes between v6 and v7 in HTML are mirrored in LaTeX as well. There are some other small adjustments that should not affect the rendered document but simplify the LaTeX source slightly.
  • I have included support for using vagrant to run fuzz testing using libFuzzer. I have used that to find (and fix) many bugs, making the parser more resilient against "unusually" formed input that I would not have thought to test. I did this with v6 as well, but now it is built directly into the development repository. This also tests for memory leaks in the core engine. In addition to "bugs", this can also identify pathologic input that needs to be handled.
  • Performance is good – depending on the test content, it is significantly faster than MMD v6. It is usually faster than CommonMark (v 0.31.1). And sometimes it is almost getting close to md4c. Things to remember:
    • MultiMarkdown has more features than CommonMark and md4c. Some of these will necessarily cause a performance hit when compared to not using those features (such as the more complex output for # Headers #). Compatibility mode turns off most of those features, but in a few cases there will still be a slight performance cost even in compatibility mode.
    • MultiMarkdown has to be capable of returning an AST in order to be used in some situations (e.g. as a syntax highlighter for MultiMarkdown Composer.) This means it will necessarily be slower than md4c in all but the most trivial of test cases. That said, I include md4c in the benchmark testing as something of a "lower bound" to shoot for.
    • The benchmark testing (in /dev) shows comparisons between MMD 6, MMD 7, CommonMark, and md4c (if you have those installed). Additionally, it compares HTML, Compatibility, and LaTeX output in MMD 7. (NOTE: md4c installed via homebrew chokes on the many-links test file. I don't know why. Building md4c yourself from source repo works fine.)
  • The API is cleaner. I still need some testing and feedback on this, but I am generally happy so far. I've tried to make libMultiMarkdown.h more self-explanatory and more complete. That said, I have not used MMD 7 inside a "real" project yet, so this may change.
  • The command line interface is different. The code is much cleaner, but I am likely to make some changes here as I get out of the development phase and more into the "using it" phase.
  • The code is much cleaner. Still room to improve, of course!
  • So far I have been happy with the changes to edge cases in the output. I started by trying to match v6 in the test suite, but a few instances arose where it was clear that the old "correct" could be improved upon. More testing will help find instances where I should make additional fixes.

Building

To build MultiMarkdown, use CMake:

make
cd build
make

Xcode users can use:

make xcode
open build-xcode/libMultiMarkdown7.xcodeproj

Testing

make
cd build
make
ctest

You can use ctest -V in order to see more information on failed tests.

Fuzz Testing

cd fuzz
make
cd build
make
./fuzz_mmd-7

This does not work on macOS. You can use Vagrant, if installed, in order to perform fuzz testing on macOS. Please ensure you know how to properly use Vagrant.

vagrant up
vagrant ssh
cd /vagrant
cd fuzz
make
cd build
make
./fuzz_mmd-7

Contributing

Feature requests, bug reports, etc. can be submitted via the Github repository.

License

MIT License

Copyright (c) 2024-2025 Fletcher T. Penney

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

uthash License 

Copyright (c) 2003-2022, Troy D. Hanson  https://troydhanson.github.io/uthash/
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

    * Redistributions of source code must retain the above copyright
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