Reland "[regexp] Rewrite error handling"

This is a reland of e80ca24c

Original change's description:
> [regexp] Rewrite error handling
>
> This patch modifies irregexp's error handling. Instead of representing
> errors as C strings, they are represented as an enumeration value
> (RegExpError), and only converted to strings when throwing the error
> object in regexp.cc. This makes it significantly easier to integrate
> into SpiderMonkey. A few notes:
>
> 1. Depending on whether the stack overflows during parsing or
>    analysis, the stack overflow message can vary ("Stack overflow" or
>    "Maximum call stack size exceeded"). I kept that behaviour in this
>    patch, under the assumption that stack overflow messages are
>    (sadly) the sorts of things that real world code ends up depending
>    on.
>
> 2. Depending on the point in code where the error was identified,
>    invalid unicode escapes could be reported as "Invalid Unicode
>    escape", "Invalid unicode escape", or "Invalid Unicode escape
>    sequence". I fervently hope that nobody depends on the specific
>    wording of a syntax error, so I standardized on the first one. (It
>    was both the most common, and the most consistent with other
>    "Invalid X escape" messages.)
>
> 3. In addition to changing the representation, this patch also adds an
>    error_pos field to RegExpParser and RegExpCompileData, which stores
>    the position at which an error occurred. This is used by
>    SpiderMonkey to provide more helpful messages about where a syntax
>    error occurred in large regular expressions.
>
> 4. This model is closer to V8's existing MessageTemplate
>    infrastructure. I considered trying to integrate it more closely
>    with MessageTemplate, but since one of our stated goals for this
>    project was to make it easier to use irregexp outside of V8, I
>    decided to hold off.
>
> R=jgruber@chromium.org
>
> Bug: v8:10303
> Change-Id: I62605fd2def2fc539f38a7e0eefa04d36e14bbde
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2091863
> Commit-Queue: Jakob Gruber <jgruber@chromium.org>
> Reviewed-by: Jakob Gruber <jgruber@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#66784}

R=jgruber@chromium.org

Bug: v8:10303
Change-Id: Iad1f11a0e0b9e525d7499aacb56c27eff9e7c7b5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2109952Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66798}

BUILD.gn

@@ -2833,6 +2833,8 @@ v8_source_set("v8_base_without_compiler") {
     "src/regexp/regexp-compiler.h",
     "src/regexp/regexp-dotprinter.cc",
     "src/regexp/regexp-dotprinter.h",
+    "src/regexp/regexp-error.cc",
+    "src/regexp/regexp-error.h",
     "src/regexp/regexp-interpreter.cc",
     "src/regexp/regexp-interpreter.h",
     "src/regexp/regexp-macro-assembler-arch.h",

src/regexp/regexp-compiler.cc

@@ -3594,7 +3594,9 @@ template <typename... Propagators>
 class Analysis : public NodeVisitor {
  public:
   Analysis(Isolate* isolate, bool is_one_byte)
-      : isolate_(isolate), is_one_byte_(is_one_byte), error_message_(nullptr) {}
+      : isolate_(isolate),
+        is_one_byte_(is_one_byte),
+        error_(RegExpError::kNone) {}
 
   void EnsureAnalyzed(RegExpNode* that) {
     StackLimitCheck check(isolate());
@@ -3602,7 +3604,7 @@ class Analysis : public NodeVisitor {
       if (FLAG_correctness_fuzzer_suppressions) {
         FATAL("Analysis: Aborting on stack overflow");
       }
-      fail("Stack overflow");
+      fail(RegExpError::kAnalysisStackOverflow);
       return;
     }
     if (that->info()->been_analyzed || that->info()->being_analyzed) return;
@@ -3612,12 +3614,12 @@ class Analysis : public NodeVisitor {
     that->info()->been_analyzed = true;
   }
 
-  bool has_failed() { return error_message_ != nullptr; }
-  const char* error_message() {
-    DCHECK(error_message_ != nullptr);
-    return error_message_;
+  bool has_failed() { return error_ != RegExpError::kNone; }
+  RegExpError error() {
+    DCHECK(error_ != RegExpError::kNone);
+    return error_;
   }
-  void fail(const char* error_message) { error_message_ = error_message; }
+  void fail(RegExpError error) { error_ = error; }
 
   Isolate* isolate() const { return isolate_; }
 
@@ -3702,19 +3704,19 @@ class Analysis : public NodeVisitor {
  private:
   Isolate* isolate_;
   bool is_one_byte_;
-  const char* error_message_;
+  RegExpError error_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(Analysis);
 };
 
-const char* AnalyzeRegExp(Isolate* isolate, bool is_one_byte,
+RegExpError AnalyzeRegExp(Isolate* isolate, bool is_one_byte,
                           RegExpNode* node) {
   Analysis<AssertionPropagator, EatsAtLeastPropagator> analysis(isolate,
                                                                 is_one_byte);
   DCHECK_EQ(node->info()->been_analyzed, false);
   analysis.EnsureAnalyzed(node);
-  DCHECK_IMPLIES(analysis.has_failed(), analysis.error_message() != nullptr);
-  return analysis.has_failed() ? analysis.error_message() : nullptr;
+  DCHECK_IMPLIES(analysis.has_failed(), analysis.error() != RegExpError::kNone);
+  return analysis.has_failed() ? analysis.error() : RegExpError::kNone;
 }
 
 void BackReferenceNode::FillInBMInfo(Isolate* isolate, int offset, int budget,

src/regexp/regexp-compiler.h

@@ -423,10 +423,7 @@ struct PreloadState {
 // Analysis performs assertion propagation and computes eats_at_least_ values.
 // See the comments on AssertionPropagator and EatsAtLeastPropagator for more
 // details.
-//
-// This method returns nullptr on success or a null-terminated failure message
-// on failure.
-const char* AnalyzeRegExp(Isolate* isolate, bool is_one_byte, RegExpNode* node);
+RegExpError AnalyzeRegExp(Isolate* isolate, bool is_one_byte, RegExpNode* node);
 
 class FrequencyCollator {
  public:
@@ -503,18 +500,17 @@ class RegExpCompiler {
   }
 
   struct CompilationResult final {
-    explicit CompilationResult(const char* error_message)
-        : error_message(error_message) {}
+    explicit CompilationResult(RegExpError err) : error(err) {}
     CompilationResult(Object code, int registers)
         : code(code), num_registers(registers) {}
 
     static CompilationResult RegExpTooBig() {
-      return CompilationResult("RegExp too big");
+      return CompilationResult(RegExpError::kTooLarge);
     }
 
-    bool Succeeded() const { return error_message == nullptr; }
+    bool Succeeded() const { return error == RegExpError::kNone; }
 
-    const char* const error_message = nullptr;
+    const RegExpError error = RegExpError::kNone;
     Object code;
     int num_registers = 0;
   };

src/regexp/regexp-error.cc

+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/regexp/regexp-error.h"
+
+namespace v8 {
+namespace internal {
+
+const char* kRegExpErrorStrings[] = {
+#define TEMPLATE(NAME, STRING) STRING,
+    REGEXP_ERROR_MESSAGES(TEMPLATE)
+#undef TEMPLATE
+};
+
+const char* RegExpErrorString(RegExpError error) {
+  DCHECK_LT(error, RegExpError::NumErrors);
+  return kRegExpErrorStrings[static_cast<int>(error)];
+}
+
+}  // namespace internal
+}  // namespace v8

src/regexp/regexp-error.h

+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_REGEXP_REGEXP_ERROR_H_
+#define V8_REGEXP_REGEXP_ERROR_H_
+
+#include "src/base/logging.h"
+#include "src/base/macros.h"
+
+namespace v8 {
+namespace internal {
+
+#define REGEXP_ERROR_MESSAGES(T)                                          \
+  T(None, "")                                                             \
+  T(StackOverflow, "Maximum call stack size exceeded")                    \
+  T(AnalysisStackOverflow, "Stack overflow")                              \
+  T(TooLarge, "Regular expression too large")                             \
+  T(UnterminatedGroup, "Unterminated group")                              \
+  T(UnmatchedParen, "Unmatched ')'")                                      \
+  T(EscapeAtEndOfPattern, "\\ at end of pattern")                         \
+  T(InvalidPropertyName, "Invalid property name")                         \
+  T(InvalidEscape, "Invalid escape")                                      \
+  T(InvalidDecimalEscape, "Invalid decimal escape")                       \
+  T(InvalidUnicodeEscape, "Invalid Unicode escape")                       \
+  T(NothingToRepeat, "Nothing to repeat")                                 \
+  T(LoneQuantifierBrackets, "Lone quantifier brackets")                   \
+  T(RangeOutOfOrder, "numbers out of order in {} quantifier")             \
+  T(IncompleteQuantifier, "Incomplete quantifier")                        \
+  T(InvalidQuantifier, "Invalid quantifier")                              \
+  T(InvalidGroup, "Invalid group")                                        \
+  T(MultipleFlagDashes, "Multiple dashes in flag group")                  \
+  T(RepeatedFlag, "Repeated flag in flag group")                          \
+  T(InvalidFlagGroup, "Invalid flag group")                               \
+  T(TooManyCaptures, "Too many captures")                                 \
+  T(InvalidCaptureGroupName, "Invalid capture group name")                \
+  T(DuplicateCaptureGroupName, "Duplicate capture group name")            \
+  T(InvalidNamedReference, "Invalid named reference")                     \
+  T(InvalidNamedCaptureReference, "Invalid named capture referenced")     \
+  T(InvalidClassEscape, "Invalid class escape")                           \
+  T(InvalidClassPropertyName, "Invalid property name in character class") \
+  T(InvalidCharacterClass, "Invalid character class")                     \
+  T(UnterminatedCharacterClass, "Unterminated character class")           \
+  T(OutOfOrderCharacterClass, "Range out of order in character class")
+
+enum class RegExpError : uint32_t {
+#define TEMPLATE(NAME, STRING) k##NAME,
+  REGEXP_ERROR_MESSAGES(TEMPLATE)
+#undef TEMPLATE
+      NumErrors
+};
+
+V8_EXPORT_PRIVATE const char* RegExpErrorString(RegExpError error);
+
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_REGEXP_REGEXP_ERROR_H_

src/regexp/regexp-parser.cc

@@ -24,11 +24,10 @@
 namespace v8 {
 namespace internal {
 
-RegExpParser::RegExpParser(FlatStringReader* in, Handle<String>* error,
-                           JSRegExp::Flags flags, Isolate* isolate, Zone* zone)
+RegExpParser::RegExpParser(FlatStringReader* in, JSRegExp::Flags flags,
+                           Isolate* isolate, Zone* zone)
     : isolate_(isolate),
       zone_(zone),
-      error_(error),
       captures_(nullptr),
       named_captures_(nullptr),
       named_back_references_(nullptr),
@@ -81,13 +80,12 @@ void RegExpParser::Advance() {
       if (FLAG_correctness_fuzzer_suppressions) {
         FATAL("Aborting on stack overflow");
       }
-      ReportError(CStrVector(
-          MessageFormatter::TemplateString(MessageTemplate::kStackOverflow)));
+      ReportError(RegExpError::kStackOverflow);
     } else if (zone()->excess_allocation()) {
       if (FLAG_correctness_fuzzer_suppressions) {
         FATAL("Aborting on excess zone allocation");
       }
-      ReportError(CStrVector("Regular expression too large"));
+      ReportError(RegExpError::kTooLarge);
     } else {
       current_ = ReadNext<true>();
     }
@@ -139,15 +137,12 @@ bool RegExpParser::IsSyntaxCharacterOrSlash(uc32 c) {
   return false;
 }
 
-
-RegExpTree* RegExpParser::ReportError(Vector<const char> message) {
+RegExpTree* RegExpParser::ReportError(RegExpError error) {
   if (failed_) return nullptr;  // Do not overwrite any existing error.
   failed_ = true;
-  *error_ = isolate()
-                ->factory()
-                ->NewStringFromOneByte(Vector<const uint8_t>::cast(message))
-                .ToHandleChecked();
-  // Zip to the end to make sure the no more input is read.
+  error_ = error;
+  error_pos_ = position();
+  // Zip to the end to make sure no more input is read.
   current_ = kEndMarker;
   next_pos_ = in()->length();
   return nullptr;
@@ -194,14 +189,14 @@ RegExpTree* RegExpParser::ParseDisjunction() {
       case kEndMarker:
         if (state->IsSubexpression()) {
           // Inside a parenthesized group when hitting end of input.
-          return ReportError(CStrVector("Unterminated group"));
+          return ReportError(RegExpError::kUnterminatedGroup);
         }
         DCHECK_EQ(INITIAL, state->group_type());
         // Parsing completed successfully.
         return builder->ToRegExp();
       case ')': {
         if (!state->IsSubexpression()) {
-          return ReportError(CStrVector("Unmatched ')'"));
+          return ReportError(RegExpError::kUnmatchedParen);
         }
         DCHECK_NE(INITIAL, state->group_type());
 
@@ -252,7 +247,7 @@ RegExpTree* RegExpParser::ParseDisjunction() {
       case '*':
       case '+':
       case '?':
-        return ReportError(CStrVector("Nothing to repeat"));
+        return ReportError(RegExpError::kNothingToRepeat);
       case '^': {
         Advance();
         if (builder->multiline()) {
@@ -307,7 +302,7 @@ RegExpTree* RegExpParser::ParseDisjunction() {
       case '\\':
         switch (Next()) {
           case kEndMarker:
-            return ReportError(CStrVector("\\ at end of pattern"));
+            return ReportError(RegExpError::kEscapeAtEndOfPattern);
           case 'b':
             Advance(2);
             builder->AddAssertion(new (zone()) RegExpAssertion(
@@ -364,7 +359,7 @@ RegExpTree* RegExpParser::ParseDisjunction() {
                   }
                 }
               }
-              return ReportError(CStrVector("Invalid property name"));
+              return ReportError(RegExpError::kInvalidPropertyName);
             } else {
               builder->AddCharacter(p);
             }
@@ -400,7 +395,7 @@ RegExpTree* RegExpParser::ParseDisjunction() {
             // With /u, no identity escapes except for syntax characters
             // are allowed. Otherwise, all identity escapes are allowed.
             if (unicode()) {
-              return ReportError(CStrVector("Invalid escape"));
+              return ReportError(RegExpError::kInvalidEscape);
             }
             uc32 first_digit = Next();
             if (first_digit == '8' || first_digit == '9') {
@@ -414,7 +409,7 @@ RegExpTree* RegExpParser::ParseDisjunction() {
             Advance();
             if (unicode() && Next() >= '0' && Next() <= '9') {
               // With /u, decimal escape with leading 0 are not parsed as octal.
-              return ReportError(CStrVector("Invalid decimal escape"));
+              return ReportError(RegExpError::kInvalidDecimalEscape);
             }
             uc32 octal = ParseOctalLiteral();
             builder->AddCharacter(octal);
@@ -455,7 +450,7 @@ RegExpTree* RegExpParser::ParseDisjunction() {
               // ES#prod-annexB-ExtendedPatternCharacter
               if (unicode()) {
                 // With /u, invalid escapes are not treated as identity escapes.
-                return ReportError(CStrVector("Invalid unicode escape"));
+                return ReportError(RegExpError::kInvalidUnicodeEscape);
               }
               builder->AddCharacter('\\');
             } else {
@@ -473,7 +468,7 @@ RegExpTree* RegExpParser::ParseDisjunction() {
               builder->AddCharacter('x');
             } else {
               // With /u, invalid escapes are not treated as identity escapes.
-              return ReportError(CStrVector("Invalid escape"));
+              return ReportError(RegExpError::kInvalidEscape);
             }
             break;
           }
@@ -486,7 +481,7 @@ RegExpTree* RegExpParser::ParseDisjunction() {
               builder->AddCharacter('u');
             } else {
               // With /u, invalid escapes are not treated as identity escapes.
-              return ReportError(CStrVector("Invalid Unicode escape"));
+              return ReportError(RegExpError::kInvalidUnicodeEscape);
             }
             break;
           }
@@ -510,7 +505,7 @@ RegExpTree* RegExpParser::ParseDisjunction() {
               builder->AddCharacter(current());
               Advance();
             } else {
-              return ReportError(CStrVector("Invalid escape"));
+              return ReportError(RegExpError::kInvalidEscape);
             }
             break;
         }
@@ -518,13 +513,13 @@ RegExpTree* RegExpParser::ParseDisjunction() {
       case '{': {
         int dummy;
         bool parsed = ParseIntervalQuantifier(&dummy, &dummy CHECK_FAILED);
-        if (parsed) return ReportError(CStrVector("Nothing to repeat"));
+        if (parsed) return ReportError(RegExpError::kNothingToRepeat);
         V8_FALLTHROUGH;
       }
       case '}':
       case ']':
         if (unicode()) {
-          return ReportError(CStrVector("Lone quantifier brackets"));
+          return ReportError(RegExpError::kLoneQuantifierBrackets);
         }
         V8_FALLTHROUGH;
       default:
@@ -559,13 +554,12 @@ RegExpTree* RegExpParser::ParseDisjunction() {
       case '{':
         if (ParseIntervalQuantifier(&min, &max)) {
           if (max < min) {
-            return ReportError(
-                CStrVector("numbers out of order in {} quantifier"));
+            return ReportError(RegExpError::kRangeOutOfOrder);
           }
           break;
         } else if (unicode()) {
           // With /u, incomplete quantifiers are not allowed.
-          return ReportError(CStrVector("Incomplete quantifier"));
+          return ReportError(RegExpError::kIncompleteQuantifier);
         }
         continue;
       default:
@@ -581,7 +575,7 @@ RegExpTree* RegExpParser::ParseDisjunction() {
       Advance();
     }
     if (!builder->AddQuantifierToAtom(min, max, quantifier_type)) {
-      return ReportError(CStrVector("Invalid quantifier"));
+      return ReportError(RegExpError::kInvalidQuantifier);
     }
   }
 }
@@ -616,7 +610,7 @@ RegExpParser::RegExpParserState* RegExpParser::ParseOpenParenthesis(
       case 's':
       case 'm': {
         if (!FLAG_regexp_mode_modifiers) {
-          ReportError(CStrVector("Invalid group"));
+          ReportError(RegExpError::kInvalidGroup);
           return nullptr;
         }
         Advance();
@@ -625,7 +619,7 @@ RegExpParser::RegExpParserState* RegExpParser::ParseOpenParenthesis(
           switch (current()) {
             case '-':
               if (!flags_sense) {
-                ReportError(CStrVector("Multiple dashes in flag group"));
+                ReportError(RegExpError::kMultipleFlagDashes);
                 return nullptr;
               }
               flags_sense = false;
@@ -639,7 +633,7 @@ RegExpParser::RegExpParserState* RegExpParser::ParseOpenParenthesis(
               if (current() == 'm') bit = JSRegExp::kMultiline;
               if (current() == 's') bit = JSRegExp::kDotAll;
               if (((switch_on | switch_off) & bit) != 0) {
-                ReportError(CStrVector("Repeated flag in flag group"));
+                ReportError(RegExpError::kRepeatedFlag);
                 return nullptr;
               }
               if (flags_sense) {
@@ -667,7 +661,7 @@ RegExpParser::RegExpParserState* RegExpParser::ParseOpenParenthesis(
               subexpr_type = GROUPING;  // Will break us out of the outer loop.
               continue;
             default:
-              ReportError(CStrVector("Invalid flag group"));
+              ReportError(RegExpError::kInvalidFlagGroup);
               return nullptr;
           }
         }
@@ -691,13 +685,13 @@ RegExpParser::RegExpParserState* RegExpParser::ParseOpenParenthesis(
         Advance();
         break;
       default:
-        ReportError(CStrVector("Invalid group"));
+        ReportError(RegExpError::kInvalidGroup);
         return nullptr;
     }
   }
   if (subexpr_type == CAPTURE) {
     if (captures_started_ >= JSRegExp::kMaxCaptures) {
-      ReportError(CStrVector("Too many captures"));
+      ReportError(RegExpError::kTooManyCaptures);
       return nullptr;
     }
     captures_started_++;
@@ -846,20 +840,20 @@ const ZoneVector<uc16>* RegExpParser::ParseCaptureGroupName() {
     if (c == '\\' && current() == 'u') {
       Advance();
       if (!ParseUnicodeEscape(&c)) {
-        ReportError(CStrVector("Invalid Unicode escape sequence"));
+        ReportError(RegExpError::kInvalidUnicodeEscape);
         return nullptr;
       }
     }
 
     // The backslash char is misclassified as both ID_Start and ID_Continue.
     if (c == '\\') {
-      ReportError(CStrVector("Invalid capture group name"));
+      ReportError(RegExpError::kInvalidCaptureGroupName);
       return nullptr;
     }
 
     if (at_start) {
       if (!IsIdentifierStart(c)) {
-        ReportError(CStrVector("Invalid capture group name"));
+        ReportError(RegExpError::kInvalidCaptureGroupName);
         return nullptr;
       }
       push_code_unit(name, c);
@@ -870,7 +864,7 @@ const ZoneVector<uc16>* RegExpParser::ParseCaptureGroupName() {
       } else if (IsIdentifierPart(c)) {
         push_code_unit(name, c);
       } else {
-        ReportError(CStrVector("Invalid capture group name"));
+        ReportError(RegExpError::kInvalidCaptureGroupName);
         return nullptr;
       }
     }
@@ -897,7 +891,7 @@ bool RegExpParser::CreateNamedCaptureAtIndex(const ZoneVector<uc16>* name,
 
     const auto& named_capture_it = named_captures_->find(capture);
     if (named_capture_it != named_captures_->end()) {
-      ReportError(CStrVector("Duplicate capture group name"));
+      ReportError(RegExpError::kDuplicateCaptureGroupName);
       return false;
     }
   }
@@ -911,7 +905,7 @@ bool RegExpParser::ParseNamedBackReference(RegExpBuilder* builder,
                                            RegExpParserState* state) {
   // The parser is assumed to be on the '<' in \k<name>.
   if (current() != '<') {
-    ReportError(CStrVector("Invalid named reference"));
+    ReportError(RegExpError::kInvalidNamedReference);
     return false;
   }
 
@@ -944,7 +938,7 @@ void RegExpParser::PatchNamedBackReferences() {
   if (named_back_references_ == nullptr) return;
 
   if (named_captures_ == nullptr) {
-    ReportError(CStrVector("Invalid named capture referenced"));
+    ReportError(RegExpError::kInvalidNamedCaptureReference);
     return;
   }
 
@@ -965,7 +959,7 @@ void RegExpParser::PatchNamedBackReferences() {
     if (capture_it != named_captures_->end()) {
       index = (*capture_it)->index();
     } else {
-      ReportError(CStrVector("Invalid named capture referenced"));
+      ReportError(RegExpError::kInvalidNamedCaptureReference);
       return;
     }
 
@@ -1606,7 +1600,7 @@ uc32 RegExpParser::ParseClassCharacterEscape() {
       }
       if (unicode()) {
         // With /u, invalid escapes are not treated as identity escapes.
-        ReportError(CStrVector("Invalid class escape"));
+        ReportError(RegExpError::kInvalidClassEscape);
         return 0;
       }
       if ((controlLetter >= '0' && controlLetter <= '9') ||
@@ -1639,7 +1633,7 @@ uc32 RegExpParser::ParseClassCharacterEscape() {
       // ES#prod-annexB-LegacyOctalEscapeSequence
       if (unicode()) {
         // With /u, decimal escape is not interpreted as octal character code.
-        ReportError(CStrVector("Invalid class escape"));
+        ReportError(RegExpError::kInvalidClassEscape);
         return 0;
       }
       return ParseOctalLiteral();
@@ -1649,7 +1643,7 @@ uc32 RegExpParser::ParseClassCharacterEscape() {
       if (ParseHexEscape(2, &value)) return value;
       if (unicode()) {
         // With /u, invalid escapes are not treated as identity escapes.
-        ReportError(CStrVector("Invalid escape"));
+        ReportError(RegExpError::kInvalidEscape);
         return 0;
       }
       // If \x is not followed by a two-digit hexadecimal, treat it
@@ -1662,7 +1656,7 @@ uc32 RegExpParser::ParseClassCharacterEscape() {
       if (ParseUnicodeEscape(&value)) return value;
       if (unicode()) {
         // With /u, invalid escapes are not treated as identity escapes.
-        ReportError(CStrVector("Invalid unicode escape"));
+        ReportError(RegExpError::kInvalidUnicodeEscape);
         return 0;
       }
       // If \u is not followed by a two-digit hexadecimal, treat it
@@ -1677,7 +1671,7 @@ uc32 RegExpParser::ParseClassCharacterEscape() {
         Advance();
         return result;
       }
-      ReportError(CStrVector("Invalid escape"));
+      ReportError(RegExpError::kInvalidEscape);
       return 0;
     }
   }
@@ -1704,7 +1698,7 @@ void RegExpParser::ParseClassEscape(ZoneList<CharacterRange>* ranges,
         return;
       }
       case kEndMarker:
-        ReportError(CStrVector("\\ at end of pattern"));
+        ReportError(RegExpError::kEscapeAtEndOfPattern);
         return;
       case 'p':
       case 'P':
@@ -1715,7 +1709,7 @@ void RegExpParser::ParseClassEscape(ZoneList<CharacterRange>* ranges,
           ZoneVector<char> name_2(zone);
           if (!ParsePropertyClassName(&name_1, &name_2) ||
               !AddPropertyClassRange(ranges, negate, name_1, name_2)) {
-            ReportError(CStrVector("Invalid property name in character class"));
+            ReportError(RegExpError::kInvalidClassPropertyName);
           }
           *is_class_escape = true;
           return;
@@ -1734,10 +1728,6 @@ void RegExpParser::ParseClassEscape(ZoneList<CharacterRange>* ranges,
 }
 
 RegExpTree* RegExpParser::ParseCharacterClass(const RegExpBuilder* builder) {
-  static const char* kUnterminated = "Unterminated character class";
-  static const char* kRangeInvalid = "Invalid character class";
-  static const char* kRangeOutOfOrder = "Range out of order in character class";
-
   DCHECK_EQ(current(), '[');
   Advance();
   bool is_negated = false;
@@ -1770,7 +1760,7 @@ RegExpTree* RegExpParser::ParseCharacterClass(const RegExpBuilder* builder) {
         // Either end is an escaped character class. Treat the '-' verbatim.
         if (unicode()) {
           // ES2015 21.2.2.15.1 step 1.
-          return ReportError(CStrVector(kRangeInvalid));
+          return ReportError(RegExpError::kInvalidCharacterClass);
         }
         if (!is_class_1) ranges->Add(CharacterRange::Singleton(char_1), zone());
         ranges->Add(CharacterRange::Singleton('-'), zone());
@@ -1779,7 +1769,7 @@ RegExpTree* RegExpParser::ParseCharacterClass(const RegExpBuilder* builder) {
       }
       // ES2015 21.2.2.15.1 step 6.
       if (char_1 > char_2) {
-        return ReportError(CStrVector(kRangeOutOfOrder));
+        return ReportError(RegExpError::kOutOfOrderCharacterClass);
       }
       ranges->Add(CharacterRange::Range(char_1, char_2), zone());
     } else {
@@ -1787,7 +1777,7 @@ RegExpTree* RegExpParser::ParseCharacterClass(const RegExpBuilder* builder) {
     }
   }
   if (!has_more()) {
-    return ReportError(CStrVector(kUnterminated));
+    return ReportError(RegExpError::kUnterminatedCharacterClass);
   }
   Advance();
   RegExpCharacterClass::CharacterClassFlags character_class_flags;
@@ -1804,14 +1794,16 @@ bool RegExpParser::ParseRegExp(Isolate* isolate, Zone* zone,
                                FlatStringReader* input, JSRegExp::Flags flags,
                                RegExpCompileData* result) {
   DCHECK(result != nullptr);
-  RegExpParser parser(input, &result->error, flags, isolate, zone);
+  RegExpParser parser(input, flags, isolate, zone);
   RegExpTree* tree = parser.ParsePattern();
   if (parser.failed()) {
     DCHECK(tree == nullptr);
-    DCHECK(!result->error.is_null());
+    DCHECK(parser.error_ != RegExpError::kNone);
+    result->error = parser.error_;
+    result->error_pos = parser.error_pos_;
   } else {
     DCHECK(tree != nullptr);
-    DCHECK(result->error.is_null());
+    DCHECK(parser.error_ == RegExpError::kNone);
     if (FLAG_trace_regexp_parser) {
       StdoutStream os;
       tree->Print(os, zone);

src/regexp/regexp-parser.h

@@ -8,6 +8,7 @@
 #include "src/objects/js-regexp.h"
 #include "src/objects/objects.h"
 #include "src/regexp/regexp-ast.h"
+#include "src/regexp/regexp-error.h"
 #include "src/zone/zone.h"
 
 namespace v8 {
@@ -153,8 +154,8 @@ class RegExpBuilder : public ZoneObject {
 
 class V8_EXPORT_PRIVATE RegExpParser {
  public:
-  RegExpParser(FlatStringReader* in, Handle<String>* error,
-               JSRegExp::Flags flags, Isolate* isolate, Zone* zone);
+  RegExpParser(FlatStringReader* in, JSRegExp::Flags flags, Isolate* isolate,
+               Zone* zone);
 
   static bool ParseRegExp(Isolate* isolate, Zone* zone, FlatStringReader* input,
                           JSRegExp::Flags flags, RegExpCompileData* result);
@@ -202,7 +203,7 @@ class V8_EXPORT_PRIVATE RegExpParser {
 
   char ParseClassEscape();
 
-  RegExpTree* ReportError(Vector<const char> message);
+  RegExpTree* ReportError(RegExpError error);
   void Advance();
   void Advance(int dist);
   void Reset(int pos);
@@ -335,7 +336,8 @@ class V8_EXPORT_PRIVATE RegExpParser {
 
   Isolate* isolate_;
   Zone* zone_;
-  Handle<String>* error_;
+  RegExpError error_ = RegExpError::kNone;
+  int error_pos_ = 0;
   ZoneList<RegExpCapture*>* captures_;
   ZoneSet<RegExpCapture*, RegExpCaptureNameLess>* named_captures_;
   ZoneList<RegExpBackReference*>* named_back_references_;

src/regexp/regexp.cc

@@ -92,9 +92,15 @@ class RegExpImpl final : public AllStatic {
 };
 
 V8_WARN_UNUSED_RESULT
-static inline MaybeHandle<Object> ThrowRegExpException(
-    Isolate* isolate, Handle<JSRegExp> re, Handle<String> pattern,
-    Handle<String> error_text) {
+static inline MaybeHandle<Object> ThrowRegExpException(Isolate* isolate,
+                                                       Handle<JSRegExp> re,
+                                                       Handle<String> pattern,
+                                                       RegExpError error) {
+  Vector<const char> error_data = CStrVector(RegExpErrorString(error));
+  Handle<String> error_text =
+      isolate->factory()
+          ->NewStringFromOneByte(Vector<const uint8_t>::cast(error_data))
+          .ToHandleChecked();
   THROW_NEW_ERROR(
       isolate,
       NewSyntaxError(MessageTemplate::kMalformedRegExp, pattern, error_text),
@@ -102,7 +108,7 @@ static inline MaybeHandle<Object> ThrowRegExpException(
 }
 
 inline void ThrowRegExpException(Isolate* isolate, Handle<JSRegExp> re,
-                                 Handle<String> error_text) {
+                                 RegExpError error_text) {
   USE(ThrowRegExpException(isolate, re, Handle<String>(re->Pattern(), isolate),
                            error_text));
 }
@@ -408,7 +414,7 @@ bool RegExpImpl::CompileIrregexp(Isolate* isolate, Handle<JSRegExp> re,
       Compile(isolate, &zone, &compile_data, flags, pattern, sample_subject,
               is_one_byte, re->BacktrackLimit());
   if (!compilation_succeeded) {
-    DCHECK(!compile_data.error.is_null());
+    DCHECK(compile_data.error != RegExpError::kNone);
     ThrowRegExpException(isolate, re, compile_data.error);
     return false;
   }
@@ -741,8 +747,7 @@ bool RegExpImpl::Compile(Isolate* isolate, Zone* zone, RegExpCompileData* data,
                          Handle<String> sample_subject, bool is_one_byte,
                          uint32_t backtrack_limit) {
   if ((data->capture_count + 1) * 2 - 1 > RegExpMacroAssembler::kMaxRegister) {
-    data->error =
-        isolate->factory()->NewStringFromAsciiChecked("RegExp too big");
+    data->error = RegExpError::kTooLarge;
     return false;
   }
 
@@ -810,8 +815,8 @@ bool RegExpImpl::Compile(Isolate* isolate, Zone* zone, RegExpCompileData* data,
 
   if (node == nullptr) node = new (zone) EndNode(EndNode::BACKTRACK, zone);
   data->node = node;
-  if (const char* error_message = AnalyzeRegExp(isolate, is_one_byte, node)) {
-    data->error = isolate->factory()->NewStringFromAsciiChecked(error_message);
+  data->error = AnalyzeRegExp(isolate, is_one_byte, node);
+  if (data->error != RegExpError::kNone) {
     return false;
   }
 
@@ -913,13 +918,12 @@ bool RegExpImpl::Compile(Isolate* isolate, Zone* zone, RegExpCompileData* data,
     }
   }
 
-  if (result.error_message != nullptr) {
+  if (result.error != RegExpError::kNone) {
     if (FLAG_correctness_fuzzer_suppressions &&
-        strncmp(result.error_message, "Stack overflow", 15) == 0) {
+        result.error == RegExpError::kStackOverflow) {
       FATAL("Aborting on stack overflow");
     }
-    data->error =
-        isolate->factory()->NewStringFromAsciiChecked(result.error_message);
+    data->error = result.error;
   }
 
   data->code = result.code;

src/regexp/regexp.h

@@ -6,6 +6,7 @@
 #define V8_REGEXP_REGEXP_H_
 
 #include "src/objects/js-regexp.h"
+#include "src/regexp/regexp-error.h"
 
 namespace v8 {
 namespace internal {
@@ -42,7 +43,11 @@ struct RegExpCompileData {
 
   // The error message. Only used if an error occurred during parsing or
   // compilation.
-  Handle<String> error;
+  RegExpError error = RegExpError::kNone;
+
+  // The position at which the error was detected. Only used if an
+  // error occurred.
+  int error_pos = 0;
 
   // The number of capture groups, without the global capture \0.
   int capture_count = 0;

test/cctest/test-regexp.cc

@@ -76,7 +76,7 @@ static void CheckParseEq(const char* input, const char* expected,
   CHECK(v8::internal::RegExpParser::ParseRegExp(CcTest::i_isolate(), &zone,
                                                 &reader, flags, &result));
   CHECK_NOT_NULL(result.tree);
-  CHECK(result.error.is_null());
+  CHECK(result.error == RegExpError::kNone);
   std::ostringstream os;
   result.tree->Print(os, &zone);
   if (strcmp(expected, os.str().c_str()) != 0) {
@@ -94,7 +94,7 @@ static bool CheckSimple(const char* input) {
   CHECK(v8::internal::RegExpParser::ParseRegExp(
       CcTest::i_isolate(), &zone, &reader, JSRegExp::kNone, &result));
   CHECK_NOT_NULL(result.tree);
-  CHECK(result.error.is_null());
+  CHECK(result.error == RegExpError::kNone);
   return result.simple;
 }
 
@@ -112,7 +112,7 @@ static MinMaxPair CheckMinMaxMatch(const char* input) {
   CHECK(v8::internal::RegExpParser::ParseRegExp(
       CcTest::i_isolate(), &zone, &reader, JSRegExp::kNone, &result));
   CHECK_NOT_NULL(result.tree);
-  CHECK(result.error.is_null());
+  CHECK(result.error == RegExpError::kNone);
   int min_match = result.tree->min_match();
   int max_match = result.tree->max_match();
   MinMaxPair pair = { min_match, max_match };
@@ -428,9 +428,8 @@ static void ExpectError(const char* input, const char* expected,
   CHECK(!v8::internal::RegExpParser::ParseRegExp(isolate, &zone, &reader, flags,
                                                  &result));
   CHECK_NULL(result.tree);
-  CHECK(!result.error.is_null());
-  std::unique_ptr<char[]> str = result.error->ToCString(ALLOW_NULLS);
-  CHECK_EQ(0, strcmp(expected, str.get()));
+  CHECK(result.error != RegExpError::kNone);
+  CHECK_EQ(0, strcmp(expected, RegExpErrorString(result.error)));
 }
 
 
@@ -468,7 +467,7 @@ TEST(Errors) {
   ExpectError("\\k<a", kInvalidCaptureName, true);
   const char* kDuplicateCaptureName = "Duplicate capture group name";
   ExpectError("(?<a>.)(?<a>.)", kDuplicateCaptureName, true);
-  const char* kInvalidUnicodeEscape = "Invalid Unicode escape sequence";
+  const char* kInvalidUnicodeEscape = "Invalid Unicode escape";
   ExpectError("(?<\\u{FISK}", kInvalidUnicodeEscape, true);
   const char* kInvalidCaptureReferenced = "Invalid named capture referenced";
   ExpectError("\\k<a>", kInvalidCaptureReferenced, true);