Handle unclosed shortcodes

Hey,
Today I encountered an “issue” with a custom shortcode. So I’m doing basically just something like this:

function bartag_func( $atts ) {
	$atts = shortcode_atts( array(
		'foo' => 'no foo',
		'baz' => 'default baz'
	), $atts, 'bartag' );

	return "foo = {$atts['foo']}";
}
add_shortcode( 'bartag', 'bartag_func' );

The shortcode itself works fine, where I got a headache, was when I forgot in a long article just to close the shortcode. So I had

[bartag foo="test" 
// ... a lot of stuff ... 
[bartag foo="test2"]

It seems to work, because the other shortcode closed it? But it swallowed all my content in between without complaining about it. I think this should be handled somehow.

Can I e.g. check manually for content length of the shortcode?