LibRegex: Treat pattern string characters as unsigned

For example, consider the following pattern:

    new RegExp('\ud834\udf06', 'u')

With this pattern, the regex parser should insert the UTF-8 encoded
bytes 0xf0, 0x9d, 0x8c, and 0x86. However, because these characters are
currently treated as normal char types, they have a negative value since
they are all > 0x7f. Then, due to sign extension, when these characters
are cast to u64, the sign bit is preserved. The result is that these
bytes are inserted as 0xfffffffffffffff0, 0xffffffffffffff9d, etc.

Fortunately, there are only a few places where we insert bytecode with
the raw characters. In these places, be sure to treat the bytes as u8
before they are cast to u64.

1 files changed, 2 insertions, 0 deletions

diff --git a/Tests/LibRegex/Regex.cpp b/Tests/LibRegex/Regex.cpp
index 7a14f30eb9..d7630fb25d 100644
--- a/Tests/LibRegex/Regex.cpp
+++ b/Tests/LibRegex/Regex.cpp
@@ -687,6 +687,8 @@ TEST_CASE(ECMA262_unicode_match)
         ECMAScriptFlags options {};
     };
     _test tests[] {
+        { "\xf0\x9d\x8c\x86"sv, "abcdef"sv, false, ECMAScriptFlags::Unicode },
+        { "[\xf0\x9d\x8c\x86]"sv, "abcdef"sv, false, ECMAScriptFlags::Unicode },
         { "\\ud83d"sv, "😀"sv, true },
         { "\\ud83d"sv, "😀"sv, false, ECMAScriptFlags::Unicode },
         { "\\ude00"sv, "😀"sv, true },