LibRegex: Take ownership of pattern string and fix move operations

The Regex object created a copy of the pattern string anyways, so tweak
the constructor to allow callers to move() pattern strings into the
regex.

The Regex move constructor and assignment operator currently result in
memory corruption. The Regex object stores a Matcher object, which holds
a reference to the Regex object. So when the Regex object is moved, that
reference is no longer valid. To fix this, the reference stored in the
Matcher must be updated when the Regex is moved.

2 files changed, 50 insertions, 22 deletions

diff --git a/Userland/Libraries/LibRegex/RegexMatcher.cpp b/Userland/Libraries/LibRegex/RegexMatcher.cpp
index f4a848741a..bd9680d41a 100644
--- a/Userland/Libraries/LibRegex/RegexMatcher.cpp
+++ b/Userland/Libraries/LibRegex/RegexMatcher.cpp
@@ -19,22 +19,45 @@ static RegexDebug s_regex_dbg(stderr);
 #endif
 
 template<class Parser>
-Regex<Parser>::Regex(StringView pattern, typename ParserTraits<Parser>::OptionsType regex_options)
+Regex<Parser>::Regex(String pattern, typename ParserTraits<Parser>::OptionsType regex_options)
+    : pattern_value(move(pattern))
 {
-    pattern_value = pattern.to_string();
-    regex::Lexer lexer(pattern);
+    regex::Lexer lexer(pattern_value);
 
     Parser parser(lexer, regex_options);
     parser_result = parser.parse();
 
     if (parser_result.error == regex::Error::NoError)
-        matcher = make<Matcher<Parser>>(*this, regex_options);
+        matcher = make<Matcher<Parser>>(this, regex_options);
+}
+
+template<class Parser>
+Regex<Parser>::Regex(Regex&& regex)
+    : pattern_value(move(regex.pattern_value))
+    , parser_result(move(regex.parser_result))
+    , matcher(move(regex.matcher))
+    , start_offset(regex.start_offset)
+{
+    if (matcher)
+        matcher->reset_pattern({}, this);
+}
+
+template<class Parser>
+Regex<Parser>& Regex<Parser>::operator=(Regex&& regex)
+{
+    pattern_value = move(regex.pattern_value);
+    parser_result = move(regex.parser_result);
+    matcher = move(regex.matcher);
+    if (matcher)
+        matcher->reset_pattern({}, this);
+    start_offset = regex.start_offset;
+    return *this;
 }
 
 template<class Parser>
 typename ParserTraits<Parser>::OptionsType Regex<Parser>::options() const
 {
-    if (parser_result.error != Error::NoError)
+    if (!matcher || parser_result.error != Error::NoError)
         return {};
 
     return matcher->options();
@@ -71,7 +94,7 @@ RegexResult Matcher<Parser>::match(Vector<RegexStringView> const views, Optional
 {
     // If the pattern *itself* isn't stateful, reset any changes to start_offset.
     if (!((AllFlags)m_regex_options.value() & AllFlags::Internal_Stateful))
-        m_pattern.start_offset = 0;
+        m_pattern->start_offset = 0;
 
     size_t match_count { 0 };
 
@@ -80,7 +103,7 @@ RegexResult Matcher<Parser>::match(Vector<RegexStringView> const views, Optional
     MatchOutput output;
 
     input.regex_options = m_regex_options | regex_options.value_or({}).value();
-    input.start_offset = m_pattern.start_offset;
+    input.start_offset = m_pattern->start_offset;
     output.operations = 0;
     size_t lines_to_skip = 0;
 
@@ -107,8 +130,8 @@ RegexResult Matcher<Parser>::match(Vector<RegexStringView> const views, Optional
         state.capture_group_matches.ensure_capacity(c_match_preallocation_count);
         state.named_capture_group_matches.ensure_capacity(c_match_preallocation_count);
 
-        auto& capture_groups_count = m_pattern.parser_result.capture_groups_count;
-        auto& named_capture_groups_count = m_pattern.parser_result.named_capture_groups_count;
+        auto& capture_groups_count = m_pattern->parser_result.capture_groups_count;
+        auto& named_capture_groups_count = m_pattern->parser_result.named_capture_groups_count;
 
         for (size_t j = 0; j < c_match_preallocation_count; ++j) {
             state.matches.empend();
@@ -152,11 +175,11 @@ RegexResult Matcher<Parser>::match(Vector<RegexStringView> const views, Optional
         dbgln_if(REGEX_DEBUG, "[match] Starting match with view ({}): _{}_", view.length(), view);
 
         auto view_length = view.length();
-        size_t view_index = m_pattern.start_offset;
+        size_t view_index = m_pattern->start_offset;
         state.string_position = view_index;
         bool succeeded = false;
 
-        if (view_index == view_length && m_pattern.parser_result.match_length_minimum == 0) {
+        if (view_index == view_length && m_pattern->parser_result.match_length_minimum == 0) {
             // Run the code until it tries to consume something.
             // This allows non-consuming code to run on empty strings, for instance
             // e.g. "Exit"
@@ -183,7 +206,7 @@ RegexResult Matcher<Parser>::match(Vector<RegexStringView> const views, Optional
         }
 
         for (; view_index < view_length; ++view_index) {
-            auto& match_length_minimum = m_pattern.parser_result.match_length_minimum;
+            auto& match_length_minimum = m_pattern->parser_result.match_length_minimum;
             // FIXME: More performant would be to know the remaining minimum string
             //        length needed to match from the current position onwards within
             //        the vm. Add new OpCode for MinMatchLengthFromSp with the value of
@@ -249,7 +272,7 @@ RegexResult Matcher<Parser>::match(Vector<RegexStringView> const views, Optional
         input.global_offset += view.length() + 1; // +1 includes the line break character
 
         if (input.regex_options.has_flag_set(AllFlags::Internal_Stateful))
-            m_pattern.start_offset = state.string_position;
+            m_pattern->start_offset = state.string_position;
 
         if (succeeded && !continue_search)
             break;
@@ -262,7 +285,7 @@ RegexResult Matcher<Parser>::match(Vector<RegexStringView> const views, Optional
         if (output_copy.capture_group_matches.size() < match_count)
             output_copy.capture_group_matches.resize(match_count);
         for (auto& matches : output_copy.capture_group_matches)
-            matches.resize(m_pattern.parser_result.capture_groups_count + 1);
+            matches.resize(m_pattern->parser_result.capture_groups_count + 1);
         if (!input.regex_options.has_flag_set(AllFlags::SkipTrimEmptyMatches)) {
             for (auto& matches : output_copy.capture_group_matches)
                 matches.template remove_all_matching([](auto& match) { return match.view.is_null(); });
@@ -286,8 +309,8 @@ RegexResult Matcher<Parser>::match(Vector<RegexStringView> const views, Optional
         move(output_copy.capture_group_matches),
         move(output_copy.named_capture_group_matches),
         output.operations,
-        m_pattern.parser_result.capture_groups_count,
-        m_pattern.parser_result.named_capture_groups_count,
+        m_pattern->parser_result.capture_groups_count,
+        m_pattern->parser_result.named_capture_groups_count,
     };
 }
 
@@ -301,7 +324,7 @@ Optional<bool> Matcher<Parser>::execute(MatchInput const& input, MatchState& sta
     MatchState fork_high_prio_state;
     Optional<bool> success;
 
-    auto& bytecode = m_pattern.parser_result.bytecode;
+    auto& bytecode = m_pattern->parser_result.bytecode;
 
     for (;;) {
         ++output.operations;
diff --git a/Userland/Libraries/LibRegex/RegexMatcher.h b/Userland/Libraries/LibRegex/RegexMatcher.h
index 965fb02695..35e72962ce 100644
--- a/Userland/Libraries/LibRegex/RegexMatcher.h
+++ b/Userland/Libraries/LibRegex/RegexMatcher.h
@@ -44,7 +44,7 @@ template<class Parser>
 class Matcher final {
 
 public:
-    Matcher(Regex<Parser> const& pattern, Optional<typename ParserTraits<Parser>::OptionsType> regex_options = {})
+    Matcher(Regex<Parser> const* pattern, Optional<typename ParserTraits<Parser>::OptionsType> regex_options = {})
         : m_pattern(pattern)
         , m_regex_options(regex_options.value_or({}))
     {
@@ -59,11 +59,16 @@ public:
         return m_regex_options;
     }
 
+    void reset_pattern(Badge<Regex<Parser>>, Regex<Parser> const* pattern)
+    {
+        m_pattern = pattern;
+    }
+
 private:
     Optional<bool> execute(MatchInput const& input, MatchState& state, MatchOutput& output, size_t recursion_level) const;
     ALWAYS_INLINE Optional<bool> execute_low_prio_forks(MatchInput const& input, MatchState& original_state, MatchOutput& output, Vector<MatchState> states, size_t recursion_level) const;
 
-    Regex<Parser> const& m_pattern;
+    Regex<Parser> const* m_pattern;
     typename ParserTraits<Parser>::OptionsType const m_regex_options;
 };
 
@@ -75,10 +80,10 @@ public:
     OwnPtr<Matcher<Parser>> matcher { nullptr };
     mutable size_t start_offset { 0 };
 
-    explicit Regex(StringView pattern, typename ParserTraits<Parser>::OptionsType regex_options = {});
+    explicit Regex(String pattern, typename ParserTraits<Parser>::OptionsType regex_options = {});
     ~Regex() = default;
-    Regex(Regex&&) = default;
-    Regex& operator=(Regex&&) = default;
+    Regex(Regex&&);
+    Regex& operator=(Regex&&);
 
     typename ParserTraits<Parser>::OptionsType options() const;
     void print_bytecode(FILE* f = stdout) const;