LibRegex: Explicitly check if a character falls into a table-based range

Previously, for a regex such as /[a-sy-z]/i, we would incorrectly think
the character "u" fell into the range "a-s" because neither of the
conditions "u > s && U > s" or "u < a && U < a" would be true, resulting
in the lookup falling back to assuming the character is in the range.

Instead, first explicitly check if the character falls into the range,
rather than checking if it falls outside the range. If the explicit
checks fail, then we know the character is outside the range.

1 files changed, 7 insertions, 4 deletions

diff --git a/Userland/Libraries/LibRegex/RegexByteCode.cpp b/Userland/Libraries/LibRegex/RegexByteCode.cpp
index ace32620fc..e0c0ca4a27 100644
--- a/Userland/Libraries/LibRegex/RegexByteCode.cpp
+++ b/Userland/Libraries/LibRegex/RegexByteCode.cpp
@@ -557,11 +557,14 @@ ALWAYS_INLINE ExecutionResult OpCode_Compare::execute(MatchInput const& input, M
                     upper_case_needle = to_ascii_uppercase(needle);
                     lower_case_needle = to_ascii_lowercase(needle);
                 }
-                if (lower_case_needle > range.to && upper_case_needle > range.to)
+
+                if (lower_case_needle >= range.from && lower_case_needle <= range.to)
+                    return 0;
+                if (upper_case_needle >= range.from && upper_case_needle <= range.to)
+                    return 0;
+                if (lower_case_needle > range.to || upper_case_needle > range.to)
                     return 1;
-                if (lower_case_needle < range.from && upper_case_needle < range.from)
-                    return -1;
-                return 0;
+                return -1;
             });
 
             if (matching_range) {