RGBCube/serenity
1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-05-30 23:08:11 +00:00
Code Issues Activity Actions

LibRegex: Make infinite repetitions short-circuit on empty matches

Browse source 
This makes (addmittedly weird) patterns like `(a*)*` work correctly
without going into an infinite fork loop.
This commit is contained in:
Ali Mohammad Pur 2021-09-06 02:38:47 +04:30 • committed by Ali Mohammad Pur
parent f8570bd773
commit abbe9da255
4 changed files with 131 additions and 69 deletions
Download patch file Download diff file Expand all files Collapse all files

15
Tests/LibRegex/Regex.cpp
View file

@ -852,6 +852,21 @@ TEST_CASE(extremely_long_fork_chain)
EXPECT_EQ(result.success, true);
}
TEST_CASE(theoretically_infinite_loop)
{
Array patterns {
"(a*)*"sv, // Infinitely matching empty substrings, the outer loop should short-circuit.
"(a*?)*"sv, // Infinitely matching empty substrings, the outer loop should short-circuit.
"(a*)*?"sv, // Should match exactly nothing.
"(?:)*?"sv, // Should not generate an infinite fork loop.
};
for (auto& pattern : patterns) {
Regex<ECMA262> re(pattern);
auto result = re.match("");
EXPECT_EQ(result.success, true);
}
}
static auto g_lots_of_a_s = String::repeated('a', 10'000'000);
BENCHMARK_CASE(fork_performance)

108
Userland/Libraries/LibRegex/RegexByteCode.cpp
View file

@ -46,6 +46,22 @@ char const* execution_result_name(ExecutionResult result)
}
}
char const* opcode_id_name(OpCodeId opcode)
{
switch (opcode) {
#define __ENUMERATE_OPCODE(x) \
case OpCodeId::x: \
return #x;
ENUMERATE_OPCODES
#undef __ENUMERATE_OPCODE
default:
VERIFY_NOT_REACHED();
return "<Unknown>";
}
}
char const* boundary_check_type_name(BoundaryCheckType ty)
{
switch (ty) {
@ -144,60 +160,14 @@ void ByteCode::ensure_opcodes_initialized()
return;
for (u32 i = (u32)OpCodeId::First; i <= (u32)OpCodeId::Last; ++i) {
switch ((OpCodeId)i) {
case OpCodeId::Exit:
s_opcodes[i] = make<OpCode_Exit>();
break;
case OpCodeId::Jump:
s_opcodes[i] = make<OpCode_Jump>();
break;
case OpCodeId::Compare:
s_opcodes[i] = make<OpCode_Compare>();
break;
case OpCodeId::CheckEnd:
s_opcodes[i] = make<OpCode_CheckEnd>();
break;
case OpCodeId::CheckBoundary:
s_opcodes[i] = make<OpCode_CheckBoundary>();
break;
case OpCodeId::ForkJump:
s_opcodes[i] = make<OpCode_ForkJump>();
break;
case OpCodeId::ForkStay:
s_opcodes[i] = make<OpCode_ForkStay>();
break;
case OpCodeId::FailForks:
s_opcodes[i] = make<OpCode_FailForks>();
break;
case OpCodeId::Save:
s_opcodes[i] = make<OpCode_Save>();
break;
case OpCodeId::Restore:
s_opcodes[i] = make<OpCode_Restore>();
break;
case OpCodeId::GoBack:
s_opcodes[i] = make<OpCode_GoBack>();
break;
case OpCodeId::CheckBegin:
s_opcodes[i] = make<OpCode_CheckBegin>();
break;
case OpCodeId::ClearCaptureGroup:
s_opcodes[i] = make<OpCode_ClearCaptureGroup>();
break;
case OpCodeId::SaveLeftCaptureGroup:
s_opcodes[i] = make<OpCode_SaveLeftCaptureGroup>();
break;
case OpCodeId::SaveRightCaptureGroup:
s_opcodes[i] = make<OpCode_SaveRightCaptureGroup>();
break;
case OpCodeId::SaveRightNamedCaptureGroup:
s_opcodes[i] = make<OpCode_SaveRightNamedCaptureGroup>();
break;
case OpCodeId::Repeat:
s_opcodes[i] = make<OpCode_Repeat>();
break;
case OpCodeId::ResetRepeat:
s_opcodes[i] = make<OpCode_ResetRepeat>();
break;
#define __ENUMERATE_OPCODE(OpCode) \
case OpCodeId::OpCode: \
s_opcodes[i] = make<OpCode_##OpCode>(); \
break;
ENUMERATE_OPCODES
#undef __ENUMERATE_OPCODE
}
}
s_opcodes_initialized = true;
@ -901,4 +871,34 @@ ALWAYS_INLINE ExecutionResult OpCode_ResetRepeat::execute(MatchInput const&, Mat
return ExecutionResult::Continue;
}
ALWAYS_INLINE ExecutionResult OpCode_Checkpoint::execute(MatchInput const&, MatchState& state) const
{
state.checkpoints.set(state.instruction_position, state.string_position);
return ExecutionResult::Continue;
}
ALWAYS_INLINE ExecutionResult OpCode_JumpNonEmpty::execute(MatchInput const&, MatchState& state) const
{
auto current_position = state.string_position;
auto checkpoint_ip = state.instruction_position + size() + checkpoint();
if (state.checkpoints.get(checkpoint_ip).value_or(current_position) != current_position) {
auto form = this->form();
if (form == OpCodeId::Jump) {
state.instruction_position += offset();
return ExecutionResult::Continue;
}
state.fork_at_position = state.instruction_position + size() + offset();
if (form == OpCodeId::ForkJump)
return ExecutionResult::Fork_PrioHigh;
if (form == OpCodeId::ForkStay)
return ExecutionResult::Fork_PrioLow;
}
return ExecutionResult::Continue;
}
}

76
Userland/Libraries/LibRegex/RegexByteCode.h
View file

@ -27,6 +27,7 @@ using ByteCodeValueType = u64;
#define ENUMERATE_OPCODES \
__ENUMERATE_OPCODE(Compare) \
__ENUMERATE_OPCODE(Jump) \
__ENUMERATE_OPCODE(JumpNonEmpty) \
__ENUMERATE_OPCODE(ForkJump) \
__ENUMERATE_OPCODE(ForkStay) \
__ENUMERATE_OPCODE(FailForks) \
@ -42,6 +43,7 @@ using ByteCodeValueType = u64;
__ENUMERATE_OPCODE(ClearCaptureGroup) \
__ENUMERATE_OPCODE(Repeat) \
__ENUMERATE_OPCODE(ResetRepeat) \
__ENUMERATE_OPCODE(Checkpoint) \
__ENUMERATE_OPCODE(Exit)
// clang-format off
@ -319,16 +321,14 @@ public:
empend(static_cast<ByteCodeValueType>(OpCodeId::ForkJump));
empend(right.size() + 2); // Jump to the _ALT label
for (auto& op : right)
append(move(op));
extend(right);
empend(static_cast<ByteCodeValueType>(OpCodeId::Jump));
empend(left.size()); // Jump to the _END label
// LABEL _ALT = bytecode.size() + 2
for (auto& op : left)
append(move(op));
extend(left);
// LABEL _END = alterantive_bytecode.size
}
@ -376,10 +376,21 @@ public:
new_bytecode[pre_loop_fork_jump_index - 1] = (ByteCodeValueType)(fork_jump_address - pre_loop_fork_jump_index);
}
} else {
// no maximum value set, repeat finding if possible
// no maximum value set, repeat finding if possible:
// (REPEAT REGEXP MIN)
// LABEL _START
// CHECKPOINT _C
// REGEXP
// JUMP_NONEMPTY _C _START FORK
// Note: This is only safe because REPEAT will leave one iteration outside (see repetition_n)
new_bytecode.insert(new_bytecode.size() - bytecode_to_repeat.size(), (ByteCodeValueType)OpCodeId::Checkpoint);
auto jump_kind = static_cast<ByteCodeValueType>(greedy ? OpCodeId::ForkJump : OpCodeId::ForkStay);
new_bytecode.empend((ByteCodeValueType)OpCodeId::JumpNonEmpty);
new_bytecode.empend(-bytecode_to_repeat.size() - 4 - 1); // Jump to the last iteration
new_bytecode.empend(-bytecode_to_repeat.size() - 4 - 1); // if _C is not empty.
new_bytecode.empend(jump_kind);
new_bytecode.empend(-bytecode_to_repeat.size() - 2); // Jump to the last iteration
}
bytecode_to_repeat = move(new_bytecode);
@ -412,23 +423,29 @@ public:
static void transform_bytecode_repetition_min_one(ByteCode& bytecode_to_repeat, bool greedy)
{
// LABEL _START = -bytecode_to_repeat.size()
// CHECKPOINT _C
// REGEXP
// FORKSTAY _START (FORKJUMP -> Greedy)
// JUMP_NONEMPTY _C _START FORKSTAY (FORKJUMP -> Greedy)
bytecode_to_repeat.prepend((ByteCodeValueType)OpCodeId::Checkpoint);
bytecode_to_repeat.empend((ByteCodeValueType)OpCodeId::JumpNonEmpty);
bytecode_to_repeat.empend(-bytecode_to_repeat.size() - 3); // Jump to the _START label...
bytecode_to_repeat.empend(-bytecode_to_repeat.size() - 2); // ...if _C is not empty
if (greedy)
bytecode_to_repeat.empend(static_cast<ByteCodeValueType>(OpCodeId::ForkJump));
else
bytecode_to_repeat.empend(static_cast<ByteCodeValueType>(OpCodeId::ForkStay));
bytecode_to_repeat.empend(-(bytecode_to_repeat.size() + 1)); // Jump to the _START label
}
static void transform_bytecode_repetition_any(ByteCode& bytecode_to_repeat, bool greedy)
{
// LABEL _START
// FORKJUMP _END (FORKSTAY -> Greedy)
// CHECKPOINT _C
// REGEXP
// JUMP _START
// JUMP_NONEMPTY _C _START JUMP
// LABEL _END
// LABEL _START = m_bytes.size();
@ -439,13 +456,17 @@ public:
else
bytecode.empend(static_cast<ByteCodeValueType>(OpCodeId::ForkJump));
bytecode.empend(bytecode_to_repeat.size() + 2); // Jump to the _END label
bytecode.empend(bytecode_to_repeat.size() + 1 + 4); // Jump to the _END label
for (auto& op : bytecode_to_repeat)
bytecode.append(move(op));
auto c_label = bytecode.size();
bytecode.empend(static_cast<ByteCodeValueType>(OpCodeId::Checkpoint));
bytecode.empend(static_cast<ByteCodeValueType>(OpCodeId::Jump));
bytecode.empend(-bytecode.size() - 1); // Jump to the _START label
bytecode.extend(bytecode_to_repeat);
bytecode.empend(static_cast<ByteCodeValueType>(OpCodeId::JumpNonEmpty));
bytecode.empend(-bytecode.size() - 3); // Jump(...) to the _START label...
bytecode.empend(c_label - bytecode.size() - 2); // ...only if _C passes.
bytecode.empend((ByteCodeValueType)OpCodeId::Jump);
// LABEL _END = bytecode.size()
bytecode_to_repeat = move(bytecode);
@ -744,6 +765,31 @@ public:
}
};
class OpCode_Checkpoint final : public OpCode {
public:
ExecutionResult execute(MatchInput const& input, MatchState& state) const override;
ALWAYS_INLINE OpCodeId opcode_id() const override { return OpCodeId::Checkpoint; }
ALWAYS_INLINE size_t size() const override { return 1; }
String const arguments_string() const override { return ""; }
};
class OpCode_JumpNonEmpty final : public OpCode {
public:
ExecutionResult execute(MatchInput const& input, MatchState& state) const override;
ALWAYS_INLINE OpCodeId opcode_id() const override { return OpCodeId::JumpNonEmpty; }
ALWAYS_INLINE size_t size() const override { return 4; }
ALWAYS_INLINE ssize_t offset() const { return argument(0); }
ALWAYS_INLINE ssize_t checkpoint() const { return argument(1); }
ALWAYS_INLINE OpCodeId form() const { return (OpCodeId)argument(2); }
String const arguments_string() const override
{
return String::formatted("{} offset={} [&{}], cp={} [&{}]",
opcode_id_name(form()),
offset(), state().instruction_position + size() + offset(),
checkpoint(), state().instruction_position + size() + checkpoint());
}
};
template<typename T>
bool is(OpCode const&);

1
Userland/Libraries/LibRegex/RegexMatch.h
View file

@ -524,6 +524,7 @@ struct MatchState {
Vector<Match> matches;
Vector<Vector<Match>> capture_group_matches;
Vector<u64> repetition_marks;
HashMap<u64, u64> checkpoints;
};
}