cmark `cmark/`

Type: Markdown Parser Library
License: BSD-2-Clause (+ MIT for some components)
Fork Origin: GitHub
Status: Detached Fork (independently maintained)
Specification: CommonMark Latest Version: 0.0.5-1

Overview

cmark is the C reference implementation of CommonMark, a strongly specified, highly compatible version of Markdown. It provides both a shared library (libcmark) and a standalone program for parsing and rendering CommonMark documents.

ProjT Launcher maintains a fork of cmark for controlled integration, CI validation, and monorepo compatibility.

Usage in ProjT Launcher

cmark is used for:

Mod descriptions — Rendering mod README files
News display — Formatting launcher news and announcements
Instance notes — User-created markdown notes
Wiki integration — Processing documentation

Features

Feature	Status
CommonMark 0.31 compliant	✅
Streaming/iterating parser	✅
Safe HTML rendering	✅
UTF-8 support	✅
Multiple output formats	✅
Extensible architecture	✅

Output Formats

HTML
Groff man pages
CommonMark (normalized)
XML
LaTeX

Build Instructions

Prerequisites

CMake 3.12+
C99 compiler (GCC, Clang, MSVC)
Python 3.6+ (for tests)

Quick Build

cd cmark
mkdir build && cd build
cmake .. -DCMAKE_BUILD_TYPE=Release
cmake --build .
ctest -V

Build Options

Option	Description	Default
`CMARK_TESTS`	Build test suite	`ON`
`CMARK_SHARED`	Build shared library	`ON`
`CMARK_STATIC`	Build static library	`OFF`
`CMARK_LIB_FUZZER`	Build libFuzzer harness	`OFF`

API Usage

Basic Example

#include <cmark.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main() {
    const char *markdown = "# Hello World\n\nThis is **CommonMark**!";
    char *html = cmark_markdown_to_html(markdown, strlen(markdown), CMARK_OPT_DEFAULT);
    printf("%s", html);
    free(html);
    return 0;
}

Streaming Parser

#include <cmark.h>

cmark_parser *parser = cmark_parser_new(CMARK_OPT_DEFAULT);
cmark_parser_feed(parser, chunk1, strlen(chunk1));
cmark_parser_feed(parser, chunk2, strlen(chunk2));
cmark_node *document = cmark_parser_finish(parser);

char *html = cmark_render_html(document, CMARK_OPT_DEFAULT);

cmark_node_free(document);
cmark_parser_free(parser);
free(html);

Safety Features

cmark is designed to be safe by default:

✅ No buffer overflows — Extensively fuzzed
✅ HTML sanitization — Safe mode available
✅ Memory safety — No use-after-free bugs
✅ Predictable output — Spec-compliant behavior

Safe Rendering Options

// Use CMARK_OPT_SAFE to prevent raw HTML passthrough
char *html = cmark_markdown_to_html(md, len, CMARK_OPT_SAFE);

Documentation

Resource	Location
API Reference	`cmark/src/cmark.h`
Man Page	`cmark/man/man3/cmark.3`
Changelog	Upstream change history
CommonMark Spec	spec.commonmark.org

Copyright & Licensing

Copyright (c) 2014, John MacFarlane

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

1. Redistributions of source code must retain the above copyright notice.
2. Redistributions in binary form must reproduce the above copyright notice.

THIS SOFTWARE IS PROVIDED "AS IS" WITHOUT WARRANTY.

Full license: cmark/COPYING

External Links

cmark GitHub
CommonMark Specification
CommonMark Dingus — Online tester
cmark-gfm — GitHub's extended fork