RDoc parses `.c` file as ruby code if markup is set to markdown in the first 3 lines

[tompng]

This file is parsed as ruby.

/* file.c */
/* :markup: markdown */
/* ↑ deleting the above line will make this file parsed as c */

#include <stdio.h>

#define def void
def foobar() {
}

/* method comment */
VALUE rb_a_foo(VALUE self) {
}

int main(){
  /* class comment */
  klass = rb_define_class("A", rb_cObject);
  rb_define_method(klass, "f", rb_a_foo, 0);
}

rdoc/lib/rdoc/parser.rb

Lines 233 to 238 in 5b15418

	markup = content.lines.first(3).grep(/markup:\s+(\w+)/) { $1 }.first
	return unless markup
	# TODO Ruby should be returned only when the filename is correct
	return RDoc::Parser::Ruby if %w[tomdoc markdown].include? markup