[php-src] Issue #8360: mbstring: UTF-8 sequences with out-of-bounds follow bytes are no longer substituted correctly

Issue: https://github.com/php/php-src/issues/8360 Comment Author: ausi > If we take \xDF\xC0 as an example, the byte \xDF is not illegal. But then \xC0 is. This is why > I made it emit a single error marker. Which totally makes sense ☺️ It took me quite some time to see how the specification ends up with two error markers here 🙈 > In general, we want mbstring to comply as closely as possible > with all relevant standards and to be compatible with as many legacy computing systems as possible. ❤️ > … I would like to ask if you have any other test cases which you can suggest should be added > to the test suite. These are the test cases I’ve written some time ago for an implementation of https://encoding.spec.whatwg.org/#utf-8-decoder (every first string is the source, second is the target) ```php ["\x80", "\u{FFFD}"], ["\xFF", "\u{FFFD}"], ["\xC2\x7F", "\u{FFFD}\x7F"], ["\xC2\x80", "\xC2\x80"], ["\xDF\xBF", "\xDF\xBF"], ["\xDF\xC0", "\u{FFFD}\u{FFFD}"], ["\xE0\xA0\x7F", "\u{FFFD}\x7F"], ["\xE0\xA0\x80", "\xE0\xA0\x80"], ["\xEF\xBF\xBF", "\xEF\xBF\xBF"], ["\xEF\xBF\xC0", "\u{FFFD}\u{FFFD}"], ["\xF0\x90\x80\x7F", "\u{FFFD}\x7F"], ["\xF0\x90\x80\x80", "\xF0\x90\x80\x80"], ["\xF4\x8F\xBF\xBF", "\xF4\x8F\xBF\xBF"], ["\xF4\x8F\xBF\xC0", "\u{FFFD}\u{FFFD}"], ["\xFA\x80\x80\x80\x80", "\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}"], ["\xFB\xBF\xBF\xBF\xBF", "\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}"], ["\xFD\x80\x80\x80\x80\x80", "\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}"], ["\xFD\xBF\xBF\xBF\xBF\xBF", "\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}"], ``` ```php return array_map(function($i) { return [chr($i), $i < 128 ? chr($i) : "\u{FFFD}"]; }, range(0, 255)); ``` There might be some test cases to borrow from libicu or the web-platform-tests but I couldn’t find them just now.