修改pods

Pods/abseil/absl/debugging/internal/demangle.cc

@@ -14,18 +14,19 @@
 
 // For reference check out:
 // https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling
-//
-// Note that we only have partial C++11 support yet.
 
 #include "absl/debugging/internal/demangle.h"
 
+#include <cstddef>
 #include <cstdint>
 #include <cstdio>
 #include <cstdlib>
+#include <cstring>
 #include <limits>
 #include <string>
 
 #include "absl/base/config.h"
+#include "absl/debugging/internal/demangle_rust.h"
 
 #if ABSL_INTERNAL_HAS_CXA_DEMANGLE
 #include <cxxabi.h>
@@ -44,14 +45,16 @@ typedef struct {
 
 // List of operators from Itanium C++ ABI.
 static const AbbrevPair kOperatorList[] = {
-    // New has special syntax (not currently supported).
+    // New has special syntax.
     {"nw", "new", 0},
     {"na", "new[]", 0},
 
-    // Works except that the 'gs' prefix is not supported.
+    // Special-cased elsewhere to support the optional gs prefix.
     {"dl", "delete", 1},
     {"da", "delete[]", 1},
 
+    {"aw", "co_await", 1},
+
     {"ps", "+", 1},  // "positive"
     {"ng", "-", 1},  // "negative"
     {"ad", "&", 1},  // "address-of"
@@ -79,6 +82,7 @@ static const AbbrevPair kOperatorList[] = {
     {"rs", ">>", 2},
     {"lS", "<<=", 2},
     {"rS", ">>=", 2},
+    {"ss", "<=>", 2},
     {"eq", "==", 2},
     {"ne", "!=", 2},
     {"lt", "<", 2},
@@ -98,6 +102,7 @@ static const AbbrevPair kOperatorList[] = {
     {"qu", "?", 3},
     {"st", "sizeof", 0},  // Special syntax
     {"sz", "sizeof", 1},  // Not a real operator name, but used in expressions.
+    {"sZ", "sizeof...", 0},  // Special syntax
     {nullptr, nullptr, 0},
 };
 
@@ -187,9 +192,50 @@ typedef struct {
   int recursion_depth;        // For stack exhaustion prevention.
   int steps;               // Cap how much work we'll do, regardless of depth.
   ParseState parse_state;  // Backtrackable state copied for most frames.
+
+  // Conditionally compiled support for marking the position of the first
+  // construct Demangle couldn't parse.  This preprocessor symbol is intended
+  // for use by Abseil demangler maintainers only; its behavior is not part of
+  // Abseil's public interface.
+#ifdef ABSL_INTERNAL_DEMANGLE_RECORDS_HIGH_WATER_MARK
+  int high_water_mark;  // Input position where parsing failed.
+  bool too_complex;  // True if any guard.IsTooComplex() call returned true.
+#endif
 } State;
 
 namespace {
+
+#ifdef ABSL_INTERNAL_DEMANGLE_RECORDS_HIGH_WATER_MARK
+void UpdateHighWaterMark(State *state) {
+  if (state->high_water_mark < state->parse_state.mangled_idx) {
+    state->high_water_mark = state->parse_state.mangled_idx;
+  }
+}
+
+void ReportHighWaterMark(State *state) {
+  // Write out the mangled name with the trouble point marked, provided that the
+  // output buffer is large enough and the mangled name did not hit a complexity
+  // limit (in which case the high water mark wouldn't point out an unparsable
+  // construct, only the point where a budget ran out).
+  const size_t input_length = std::strlen(state->mangled_begin);
+  if (input_length + 6 > static_cast<size_t>(state->out_end_idx) ||
+      state->too_complex) {
+    if (state->out_end_idx > 0) state->out[0] = '\0';
+    return;
+  }
+  const size_t high_water_mark = static_cast<size_t>(state->high_water_mark);
+  std::memcpy(state->out, state->mangled_begin, high_water_mark);
+  std::memcpy(state->out + high_water_mark, "--!--", 5);
+  std::memcpy(state->out + high_water_mark + 5,
+              state->mangled_begin + high_water_mark,
+              input_length - high_water_mark);
+  state->out[input_length + 5] = '\0';
+}
+#else
+void UpdateHighWaterMark(State *) {}
+void ReportHighWaterMark(State *) {}
+#endif
+
 // Prevent deep recursion / stack exhaustion.
 // Also prevent unbounded handling of complex inputs.
 class ComplexityGuard {
@@ -201,7 +247,7 @@ class ComplexityGuard {
   ~ComplexityGuard() { --state_->recursion_depth; }
 
   // 256 levels of recursion seems like a reasonable upper limit on depth.
-  // 128 is not enough to demagle synthetic tests from demangle_unittest.txt:
+  // 128 is not enough to demangle synthetic tests from demangle_unittest.txt:
   // "_ZaaZZZZ..." and "_ZaaZcvZcvZ..."
   static constexpr int kRecursionDepthLimit = 256;
 
@@ -222,8 +268,14 @@ class ComplexityGuard {
   static constexpr int kParseStepsLimit = 1 << 17;
 
   bool IsTooComplex() const {
-    return state_->recursion_depth > kRecursionDepthLimit ||
-           state_->steps > kParseStepsLimit;
+    if (state_->recursion_depth > kRecursionDepthLimit ||
+        state_->steps > kParseStepsLimit) {
+#ifdef ABSL_INTERNAL_DEMANGLE_RECORDS_HIGH_WATER_MARK
+      state_->too_complex = true;
+#endif
+      return true;
+    }
+    return false;
   }
 
  private:
@@ -270,6 +322,10 @@ static void InitState(State* state,
   state->out_end_idx = static_cast<int>(out_size);
   state->recursion_depth = 0;
   state->steps = 0;
+#ifdef ABSL_INTERNAL_DEMANGLE_RECORDS_HIGH_WATER_MARK
+  state->high_water_mark = 0;
+  state->too_complex = false;
+#endif
 
   state->parse_state.mangled_idx = 0;
   state->parse_state.out_cur_idx = 0;
@@ -291,13 +347,14 @@ static bool ParseOneCharToken(State *state, const char one_char_token) {
   if (guard.IsTooComplex()) return false;
   if (RemainingInput(state)[0] == one_char_token) {
     ++state->parse_state.mangled_idx;
+    UpdateHighWaterMark(state);
     return true;
   }
   return false;
 }
 
-// Returns true and advances "mangled_cur" if we find "two_char_token"
-// at "mangled_cur" position.  It is assumed that "two_char_token" does
+// Returns true and advances "mangled_idx" if we find "two_char_token"
+// at "mangled_idx" position.  It is assumed that "two_char_token" does
 // not contain '\0'.
 static bool ParseTwoCharToken(State *state, const char *two_char_token) {
   ComplexityGuard guard(state);
@@ -305,11 +362,45 @@ static bool ParseTwoCharToken(State *state, const char *two_char_token) {
   if (RemainingInput(state)[0] == two_char_token[0] &&
       RemainingInput(state)[1] == two_char_token[1]) {
     state->parse_state.mangled_idx += 2;
+    UpdateHighWaterMark(state);
     return true;
   }
   return false;
 }
 
+// Returns true and advances "mangled_idx" if we find "three_char_token"
+// at "mangled_idx" position.  It is assumed that "three_char_token" does
+// not contain '\0'.
+static bool ParseThreeCharToken(State *state, const char *three_char_token) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  if (RemainingInput(state)[0] == three_char_token[0] &&
+      RemainingInput(state)[1] == three_char_token[1] &&
+      RemainingInput(state)[2] == three_char_token[2]) {
+    state->parse_state.mangled_idx += 3;
+    UpdateHighWaterMark(state);
+    return true;
+  }
+  return false;
+}
+
+// Returns true and advances "mangled_idx" if we find a copy of the
+// NUL-terminated string "long_token" at "mangled_idx" position.
+static bool ParseLongToken(State *state, const char *long_token) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  int i = 0;
+  for (; long_token[i] != '\0'; ++i) {
+    // Note that we cannot run off the end of the NUL-terminated input here.
+    // Inside the loop body, long_token[i] is known to be different from NUL.
+    // So if we read the NUL on the end of the input here, we return at once.
+    if (RemainingInput(state)[i] != long_token[i]) return false;
+  }
+  state->parse_state.mangled_idx += i;
+  UpdateHighWaterMark(state);
+  return true;
+}
+
 // Returns true and advances "mangled_cur" if we find any character in
 // "char_class" at "mangled_cur" position.
 static bool ParseCharClass(State *state, const char *char_class) {
@@ -322,6 +413,7 @@ static bool ParseCharClass(State *state, const char *char_class) {
   for (; *p != '\0'; ++p) {
     if (RemainingInput(state)[0] == *p) {
       ++state->parse_state.mangled_idx;
+      UpdateHighWaterMark(state);
       return true;
     }
   }
@@ -554,6 +646,7 @@ static bool ParseFloatNumber(State *state);
 static bool ParseSeqId(State *state);
 static bool ParseIdentifier(State *state, size_t length);
 static bool ParseOperatorName(State *state, int *arity);
+static bool ParseConversionOperatorType(State *state);
 static bool ParseSpecialName(State *state);
 static bool ParseCallOffset(State *state);
 static bool ParseNVOffset(State *state);
@@ -563,21 +656,33 @@ static bool ParseCtorDtorName(State *state);
 static bool ParseDecltype(State *state);
 static bool ParseType(State *state);
 static bool ParseCVQualifiers(State *state);
+static bool ParseExtendedQualifier(State *state);
 static bool ParseBuiltinType(State *state);
+static bool ParseVendorExtendedType(State *state);
 static bool ParseFunctionType(State *state);
 static bool ParseBareFunctionType(State *state);
+static bool ParseOverloadAttribute(State *state);
 static bool ParseClassEnumType(State *state);
 static bool ParseArrayType(State *state);
 static bool ParsePointerToMemberType(State *state);
 static bool ParseTemplateParam(State *state);
+static bool ParseTemplateParamDecl(State *state);
 static bool ParseTemplateTemplateParam(State *state);
 static bool ParseTemplateArgs(State *state);
 static bool ParseTemplateArg(State *state);
 static bool ParseBaseUnresolvedName(State *state);
 static bool ParseUnresolvedName(State *state);
+static bool ParseUnresolvedQualifierLevel(State *state);
+static bool ParseUnionSelector(State* state);
+static bool ParseFunctionParam(State* state);
+static bool ParseBracedExpression(State *state);
 static bool ParseExpression(State *state);
+static bool ParseInitializer(State *state);
 static bool ParseExprPrimary(State *state);
-static bool ParseExprCastValue(State *state);
+static bool ParseExprCastValueAndTrailingE(State *state);
+static bool ParseQRequiresClauseExpr(State *state);
+static bool ParseRequirement(State *state);
+static bool ParseTypeConstraint(State *state);
 static bool ParseLocalName(State *state);
 static bool ParseLocalNameSuffix(State *state);
 static bool ParseDiscriminator(State *state);
@@ -622,22 +727,34 @@ static bool ParseMangledName(State *state) {
 }
 
 // <encoding> ::= <(function) name> <bare-function-type>
+//                [`Q` <requires-clause expr>]
 //            ::= <(data) name>
 //            ::= <special-name>
+//
+// NOTE: Based on http://shortn/_Hoq9qG83rx
 static bool ParseEncoding(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
-  // Implementing the first two productions together as <name>
-  // [<bare-function-type>] avoids exponential blowup of backtracking.
+  // Since the first two productions both start with <name>, attempt
+  // to parse it only once to avoid exponential blowup of backtracking.
   //
-  // Since Optional(...) can't fail, there's no need to copy the state for
-  // backtracking.
-  if (ParseName(state) && Optional(ParseBareFunctionType(state))) {
+  // We're careful about exponential blowup because <encoding> recursively
+  // appears in other productions downstream of its first two productions,
+  // which means that every call to `ParseName` would possibly indirectly
+  // result in two calls to `ParseName` etc.
+  if (ParseName(state)) {
+    if (!ParseBareFunctionType(state)) {
+      return true;  // <(data) name>
+    }
+
+    // Parsed: <(function) name> <bare-function-type>
+    // Pending: [`Q` <requires-clause expr>]
+    ParseQRequiresClauseExpr(state);  // restores state on failure
     return true;
   }
 
   if (ParseSpecialName(state)) {
-    return true;
+    return true;  // <special-name>
   }
   return false;
 }
@@ -723,19 +840,26 @@ static bool ParseNestedName(State *state) {
 // <prefix> ::= <prefix> <unqualified-name>
 //          ::= <template-prefix> <template-args>
 //          ::= <template-param>
+//          ::= <decltype>
 //          ::= <substitution>
 //          ::= # empty
 // <template-prefix> ::= <prefix> <(template) unqualified-name>
 //                   ::= <template-param>
 //                   ::= <substitution>
+//                   ::= <vendor-extended-type>
 static bool ParsePrefix(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
   bool has_something = false;
   while (true) {
     MaybeAppendSeparator(state);
-    if (ParseTemplateParam(state) ||
+    if (ParseTemplateParam(state) || ParseDecltype(state) ||
         ParseSubstitution(state, /*accept_std=*/true) ||
+        // Although the official grammar does not mention it, nested-names
+        // shaped like Nu14__some_builtinIiE6memberE occur in practice, and it
+        // is not clear what else a compiler is supposed to do when a
+        // vendor-extended type has named members.
+        ParseVendorExtendedType(state) ||
         ParseUnscopedName(state) ||
         (ParseOneCharToken(state, 'M') && ParseUnnamedTypeName(state))) {
       has_something = true;
@@ -757,8 +881,14 @@ static bool ParsePrefix(State *state) {
 //                    ::= <source-name> [<abi-tags>]
 //                    ::= <local-source-name> [<abi-tags>]
 //                    ::= <unnamed-type-name> [<abi-tags>]
+//                    ::= DC <source-name>+ E  # C++17 structured binding
+//                    ::= F <source-name>  # C++20 constrained friend
+//                    ::= F <operator-name>  # C++20 constrained friend
 //
 // <local-source-name> is a GCC extension; see below.
+//
+// For the F notation for constrained friends, see
+// https://github.com/itanium-cxx-abi/cxx-abi/issues/24#issuecomment-1491130332.
 static bool ParseUnqualifiedName(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
@@ -767,6 +897,23 @@ static bool ParseUnqualifiedName(State *state) {
       ParseUnnamedTypeName(state)) {
     return ParseAbiTags(state);
   }
+
+  // DC <source-name>+ E
+  ParseState copy = state->parse_state;
+  if (ParseTwoCharToken(state, "DC") && OneOrMore(ParseSourceName, state) &&
+      ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // F <source-name>
+  // F <operator-name>
+  if (ParseOneCharToken(state, 'F') && MaybeAppend(state, "friend ") &&
+      (ParseSourceName(state) || ParseOperatorName(state, nullptr))) {
+    return true;
+  }
+  state->parse_state = copy;
+
   return false;
 }
 
@@ -824,7 +971,11 @@ static bool ParseLocalSourceName(State *state) {
 // <unnamed-type-name> ::= Ut [<(nonnegative) number>] _
 //                     ::= <closure-type-name>
 // <closure-type-name> ::= Ul <lambda-sig> E [<(nonnegative) number>] _
-// <lambda-sig>        ::= <(parameter) type>+
+// <lambda-sig>        ::= <template-param-decl>* <(parameter) type>+
+//
+// For <template-param-decl>* in <lambda-sig> see:
+//
+// https://github.com/itanium-cxx-abi/cxx-abi/issues/31
 static bool ParseUnnamedTypeName(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
@@ -847,6 +998,7 @@ static bool ParseUnnamedTypeName(State *state) {
   // Closure type.
   which = -1;
   if (ParseTwoCharToken(state, "Ul") && DisableAppend(state) &&
+      ZeroOrMore(ParseTemplateParamDecl, state) &&
       OneOrMore(ParseType, state) && RestoreAppend(state, copy.append) &&
       ParseOneCharToken(state, 'E') && Optional(ParseNumber(state, &which)) &&
       which <= std::numeric_limits<int>::max() - 2 &&  // Don't overflow.
@@ -888,6 +1040,7 @@ static bool ParseNumber(State *state, int *number_out) {
   }
   if (p != RemainingInput(state)) {  // Conversion succeeded.
     state->parse_state.mangled_idx += p - RemainingInput(state);
+    UpdateHighWaterMark(state);
     if (number_out != nullptr) {
       // Note: possibly truncate "number".
       *number_out = static_cast<int>(number);
@@ -910,6 +1063,7 @@ static bool ParseFloatNumber(State *state) {
   }
   if (p != RemainingInput(state)) {  // Conversion succeeded.
     state->parse_state.mangled_idx += p - RemainingInput(state);
+    UpdateHighWaterMark(state);
     return true;
   }
   return false;
@@ -928,6 +1082,7 @@ static bool ParseSeqId(State *state) {
   }
   if (p != RemainingInput(state)) {  // Conversion succeeded.
     state->parse_state.mangled_idx += p - RemainingInput(state);
+    UpdateHighWaterMark(state);
     return true;
   }
   return false;
@@ -946,11 +1101,13 @@ static bool ParseIdentifier(State *state, size_t length) {
     MaybeAppendWithLength(state, RemainingInput(state), length);
   }
   state->parse_state.mangled_idx += length;
+  UpdateHighWaterMark(state);
   return true;
 }
 
 // <operator-name> ::= nw, and other two letters cases
 //                 ::= cv <type>  # (cast)
+//                 ::= li <source-name>  # C++11 user-defined literal
 //                 ::= v  <digit> <source-name> # vendor extended operator
 static bool ParseOperatorName(State *state, int *arity) {
   ComplexityGuard guard(state);
@@ -961,7 +1118,7 @@ static bool ParseOperatorName(State *state, int *arity) {
   // First check with "cv" (cast) case.
   ParseState copy = state->parse_state;
   if (ParseTwoCharToken(state, "cv") && MaybeAppend(state, "operator ") &&
-      EnterNestedName(state) && ParseType(state) &&
+      EnterNestedName(state) && ParseConversionOperatorType(state) &&
       LeaveNestedName(state, copy.nest_level)) {
     if (arity != nullptr) {
       *arity = 1;
@@ -970,6 +1127,13 @@ static bool ParseOperatorName(State *state, int *arity) {
   }
   state->parse_state = copy;
 
+  // Then user-defined literals.
+  if (ParseTwoCharToken(state, "li") && MaybeAppend(state, "operator\"\" ") &&
+      ParseSourceName(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
   // Then vendor extended operators.
   if (ParseOneCharToken(state, 'v') && ParseDigit(state, arity) &&
       ParseSourceName(state)) {
@@ -997,36 +1161,120 @@ static bool ParseOperatorName(State *state, int *arity) {
       }
       MaybeAppend(state, p->real_name);
       state->parse_state.mangled_idx += 2;
+      UpdateHighWaterMark(state);
       return true;
     }
   }
   return false;
 }
 
+// <operator-name> ::= cv <type>  # (cast)
+//
+// The name of a conversion operator is the one place where cv-qualifiers, *, &,
+// and other simple type combinators are expected to appear in our stripped-down
+// demangling (elsewhere they appear in function signatures or template
+// arguments, which we omit from the output).  We make reasonable efforts to
+// render simple cases accurately.
+static bool ParseConversionOperatorType(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+
+  // Scan pointers, const, and other easy mangling prefixes with postfix
+  // demanglings.  Remember the range of input for later rescanning.
+  //
+  // See `ParseType` and the `switch` below for the meaning of each char.
+  const char* begin_simple_prefixes = RemainingInput(state);
+  while (ParseCharClass(state, "OPRCGrVK")) {}
+  const char* end_simple_prefixes = RemainingInput(state);
+
+  // Emit the base type first.
+  if (!ParseType(state)) {
+    state->parse_state = copy;
+    return false;
+  }
+
+  // Then rescan the easy type combinators in reverse order to emit their
+  // demanglings in the expected output order.
+  while (begin_simple_prefixes != end_simple_prefixes) {
+    switch (*--end_simple_prefixes) {
+      case 'P':
+        MaybeAppend(state, "*");
+        break;
+      case 'R':
+        MaybeAppend(state, "&");
+        break;
+      case 'O':
+        MaybeAppend(state, "&&");
+        break;
+      case 'C':
+        MaybeAppend(state, " _Complex");
+        break;
+      case 'G':
+        MaybeAppend(state, " _Imaginary");
+        break;
+      case 'r':
+        MaybeAppend(state, " restrict");
+        break;
+      case 'V':
+        MaybeAppend(state, " volatile");
+        break;
+      case 'K':
+        MaybeAppend(state, " const");
+        break;
+    }
+  }
+  return true;
+}
+
 // <special-name> ::= TV <type>
 //                ::= TT <type>
 //                ::= TI <type>
 //                ::= TS <type>
-//                ::= TH <type>  # thread-local
+//                ::= TW <name>  # thread-local wrapper
+//                ::= TH <name>  # thread-local initialization
 //                ::= Tc <call-offset> <call-offset> <(base) encoding>
 //                ::= GV <(object) name>
+//                ::= GR <(object) name> [<seq-id>] _
 //                ::= T <call-offset> <(base) encoding>
+//                ::= GTt <encoding>  # transaction-safe entry point
+//                ::= TA <template-arg>  # nontype template parameter object
 // G++ extensions:
 //                ::= TC <type> <(offset) number> _ <(base) type>
 //                ::= TF <type>
 //                ::= TJ <type>
-//                ::= GR <name>
+//                ::= GR <name>  # without final _, perhaps an earlier form?
 //                ::= GA <encoding>
 //                ::= Th <call-offset> <(base) encoding>
 //                ::= Tv <call-offset> <(base) encoding>
 //
-// Note: we don't care much about them since they don't appear in
-// stack traces.  The are special data.
+// Note: Most of these are special data, not functions that occur in stack
+// traces.  Exceptions are TW and TH, which denote functions supporting the
+// thread_local feature.  For these see:
+//
+// https://maskray.me/blog/2021-02-14-all-about-thread-local-storage
+//
+// For TA see https://github.com/itanium-cxx-abi/cxx-abi/issues/63.
 static bool ParseSpecialName(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
   ParseState copy = state->parse_state;
-  if (ParseOneCharToken(state, 'T') && ParseCharClass(state, "VTISH") &&
+
+  if (ParseTwoCharToken(state, "TW")) {
+    MaybeAppend(state, "thread-local wrapper routine for ");
+    if (ParseName(state)) return true;
+    state->parse_state = copy;
+    return false;
+  }
+
+  if (ParseTwoCharToken(state, "TH")) {
+    MaybeAppend(state, "thread-local initialization routine for ");
+    if (ParseName(state)) return true;
+    state->parse_state = copy;
+    return false;
+  }
+
+  if (ParseOneCharToken(state, 'T') && ParseCharClass(state, "VTIS") &&
       ParseType(state)) {
     return true;
   }
@@ -1064,12 +1312,30 @@ static bool ParseSpecialName(State *state) {
   }
   state->parse_state = copy;
 
-  if (ParseTwoCharToken(state, "GR") && ParseName(state)) {
+  // <special-name> ::= GR <(object) name> [<seq-id>] _  # modern standard
+  //                ::= GR <(object) name>  # also recognized
+  if (ParseTwoCharToken(state, "GR")) {
+    MaybeAppend(state, "reference temporary for ");
+    if (!ParseName(state)) {
+      state->parse_state = copy;
+      return false;
+    }
+    const bool has_seq_id = ParseSeqId(state);
+    const bool has_underscore = ParseOneCharToken(state, '_');
+    if (has_seq_id && !has_underscore) {
+      state->parse_state = copy;
+      return false;
+    }
+    return true;
+  }
+
+  if (ParseTwoCharToken(state, "GA") && ParseEncoding(state)) {
     return true;
   }
   state->parse_state = copy;
 
-  if (ParseTwoCharToken(state, "GA") && ParseEncoding(state)) {
+  if (ParseThreeCharToken(state, "GTt") &&
+      MaybeAppend(state, "transaction clone for ") && ParseEncoding(state)) {
     return true;
   }
   state->parse_state = copy;
@@ -1079,6 +1345,18 @@ static bool ParseSpecialName(State *state) {
     return true;
   }
   state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "TA")) {
+    bool append = state->parse_state.append;
+    DisableAppend(state);
+    if (ParseTemplateArg(state)) {
+      RestoreAppend(state, append);
+      MaybeAppend(state, "template parameter object");
+      return true;
+    }
+  }
+  state->parse_state = copy;
+
   return false;
 }
 
@@ -1182,7 +1460,6 @@ static bool ParseDecltype(State *state) {
 //        ::= O <type>   # rvalue reference-to (C++0x)
 //        ::= C <type>   # complex pair (C 2000)
 //        ::= G <type>   # imaginary (C 2000)
-//        ::= U <source-name> <type>  # vendor extended type qualifier
 //        ::= <builtin-type>
 //        ::= <function-type>
 //        ::= <class-enum-type>  # note: just an alias for <name>
@@ -1193,7 +1470,9 @@ static bool ParseDecltype(State *state) {
 //        ::= <decltype>
 //        ::= <substitution>
 //        ::= Dp <type>          # pack expansion of (C++0x)
-//        ::= Dv <num-elems> _   # GNU vector extension
+//        ::= Dv <(elements) number> _ <type>  # GNU vector extension
+//        ::= Dv <(bytes) expression> _ <type>
+//        ::= Dk <type-constraint>  # constrained auto
 //
 static bool ParseType(State *state) {
   ComplexityGuard guard(state);
@@ -1236,12 +1515,6 @@ static bool ParseType(State *state) {
   }
   state->parse_state = copy;
 
-  if (ParseOneCharToken(state, 'U') && ParseSourceName(state) &&
-      ParseType(state)) {
-    return true;
-  }
-  state->parse_state = copy;
-
   if (ParseBuiltinType(state) || ParseFunctionType(state) ||
       ParseClassEnumType(state) || ParseArrayType(state) ||
       ParsePointerToMemberType(state) || ParseDecltype(state) ||
@@ -1260,54 +1533,160 @@ static bool ParseType(State *state) {
     return true;
   }
 
+  // GNU vector extension Dv <number> _ <type>
   if (ParseTwoCharToken(state, "Dv") && ParseNumber(state, nullptr) &&
-      ParseOneCharToken(state, '_')) {
+      ParseOneCharToken(state, '_') && ParseType(state)) {
     return true;
   }
   state->parse_state = copy;
 
-  return false;
+  // GNU vector extension Dv <expression> _ <type>
+  if (ParseTwoCharToken(state, "Dv") && ParseExpression(state) &&
+      ParseOneCharToken(state, '_') && ParseType(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "Dk") && ParseTypeConstraint(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // For this notation see CXXNameMangler::mangleType in Clang's source code.
+  // The relevant logic and its comment "not clear how to mangle this!" date
+  // from 2011, so it may be with us awhile.
+  return ParseLongToken(state, "_SUBSTPACK_");
 }
 
+// <qualifiers> ::= <extended-qualifier>* <CV-qualifiers>
 // <CV-qualifiers> ::= [r] [V] [K]
+//
 // We don't allow empty <CV-qualifiers> to avoid infinite loop in
 // ParseType().
 static bool ParseCVQualifiers(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
   int num_cv_qualifiers = 0;
+  while (ParseExtendedQualifier(state)) ++num_cv_qualifiers;
   num_cv_qualifiers += ParseOneCharToken(state, 'r');
   num_cv_qualifiers += ParseOneCharToken(state, 'V');
   num_cv_qualifiers += ParseOneCharToken(state, 'K');
   return num_cv_qualifiers > 0;
 }
 
+// <extended-qualifier> ::= U <source-name> [<template-args>]
+static bool ParseExtendedQualifier(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+
+  if (!ParseOneCharToken(state, 'U')) return false;
+
+  bool append = state->parse_state.append;
+  DisableAppend(state);
+  if (!ParseSourceName(state)) {
+    state->parse_state = copy;
+    return false;
+  }
+  Optional(ParseTemplateArgs(state));
+  RestoreAppend(state, append);
+  return true;
+}
+
 // <builtin-type> ::= v, etc.  # single-character builtin types
-//                ::= u <source-name>
+//                ::= <vendor-extended-type>
 //                ::= Dd, etc.  # two-character builtin types
+//                ::= DB (<number> | <expression>) _  # _BitInt(N)
+//                ::= DU (<number> | <expression>) _  # unsigned _BitInt(N)
+//                ::= DF <number> _  # _FloatN (N bits)
+//                ::= DF <number> x  # _FloatNx
+//                ::= DF16b  # std::bfloat16_t
 //
 // Not supported:
-//                ::= DF <number> _ # _FloatN (N bits)
-//
+//                ::= [DS] DA <fixed-point-size>
+//                ::= [DS] DR <fixed-point-size>
+// because real implementations of N1169 fixed-point are scant.
 static bool ParseBuiltinType(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
-  const AbbrevPair *p;
-  for (p = kBuiltinTypeList; p->abbrev != nullptr; ++p) {
+  ParseState copy = state->parse_state;
+
+  // DB (<number> | <expression>) _  # _BitInt(N)
+  // DU (<number> | <expression>) _  # unsigned _BitInt(N)
+  if (ParseTwoCharToken(state, "DB") ||
+      (ParseTwoCharToken(state, "DU") && MaybeAppend(state, "unsigned "))) {
+    bool append = state->parse_state.append;
+    DisableAppend(state);
+    int number = -1;
+    if (!ParseNumber(state, &number) && !ParseExpression(state)) {
+      state->parse_state = copy;
+      return false;
+    }
+    RestoreAppend(state, append);
+
+    if (!ParseOneCharToken(state, '_')) {
+      state->parse_state = copy;
+      return false;
+    }
+
+    MaybeAppend(state, "_BitInt(");
+    if (number >= 0) {
+      MaybeAppendDecimal(state, number);
+    } else {
+      MaybeAppend(state, "?");  // the best we can do for dependent sizes
+    }
+    MaybeAppend(state, ")");
+    return true;
+  }
+
+  // DF <number> _  # _FloatN
+  // DF <number> x  # _FloatNx
+  // DF16b  # std::bfloat16_t
+  if (ParseTwoCharToken(state, "DF")) {
+    if (ParseThreeCharToken(state, "16b")) {
+      MaybeAppend(state, "std::bfloat16_t");
+      return true;
+    }
+    int number = 0;
+    if (!ParseNumber(state, &number)) {
+      state->parse_state = copy;
+      return false;
+    }
+    MaybeAppend(state, "_Float");
+    MaybeAppendDecimal(state, number);
+    if (ParseOneCharToken(state, 'x')) {
+      MaybeAppend(state, "x");
+      return true;
+    }
+    if (ParseOneCharToken(state, '_')) return true;
+    state->parse_state = copy;
+    return false;
+  }
+
+  for (const AbbrevPair *p = kBuiltinTypeList; p->abbrev != nullptr; ++p) {
     // Guaranteed only 1- or 2-character strings in kBuiltinTypeList.
     if (p->abbrev[1] == '\0') {
       if (ParseOneCharToken(state, p->abbrev[0])) {
         MaybeAppend(state, p->real_name);
-        return true;
+        return true;  // ::= v, etc.  # single-character builtin types
       }
     } else if (p->abbrev[2] == '\0' && ParseTwoCharToken(state, p->abbrev)) {
       MaybeAppend(state, p->real_name);
-      return true;
+      return true;  // ::= Dd, etc.  # two-character builtin types
     }
   }
 
+  return ParseVendorExtendedType(state);
+}
+
+// <vendor-extended-type> ::= u <source-name> [<template-args>]
+static bool ParseVendorExtendedType(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+
   ParseState copy = state->parse_state;
-  if (ParseOneCharToken(state, 'u') && ParseSourceName(state)) {
+  if (ParseOneCharToken(state, 'u') && ParseSourceName(state) &&
+      Optional(ParseTemplateArgs(state))) {
     return true;
   }
   state->parse_state = copy;
@@ -1342,28 +1721,44 @@ static bool ParseExceptionSpec(State *state) {
   return false;
 }
 
-// <function-type> ::= [exception-spec] F [Y] <bare-function-type> [O] E
+// <function-type> ::=
+//     [exception-spec] [Dx] F [Y] <bare-function-type> [<ref-qualifier>] E
+//
+// <ref-qualifier> ::= R | O
 static bool ParseFunctionType(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
   ParseState copy = state->parse_state;
-  if (Optional(ParseExceptionSpec(state)) && ParseOneCharToken(state, 'F') &&
-      Optional(ParseOneCharToken(state, 'Y')) && ParseBareFunctionType(state) &&
-      Optional(ParseOneCharToken(state, 'O')) &&
-      ParseOneCharToken(state, 'E')) {
-    return true;
+  Optional(ParseExceptionSpec(state));
+  Optional(ParseTwoCharToken(state, "Dx"));
+  if (!ParseOneCharToken(state, 'F')) {
+    state->parse_state = copy;
+    return false;
   }
-  state->parse_state = copy;
-  return false;
+  Optional(ParseOneCharToken(state, 'Y'));
+  if (!ParseBareFunctionType(state)) {
+    state->parse_state = copy;
+    return false;
+  }
+  Optional(ParseCharClass(state, "RO"));
+  if (!ParseOneCharToken(state, 'E')) {
+    state->parse_state = copy;
+    return false;
+  }
+  return true;
 }
 
-// <bare-function-type> ::= <(signature) type>+
+// <bare-function-type> ::= <overload-attribute>* <(signature) type>+
+//
+// The <overload-attribute>* prefix is nonstandard; see the comment on
+// ParseOverloadAttribute.
 static bool ParseBareFunctionType(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
   ParseState copy = state->parse_state;
   DisableAppend(state);
-  if (OneOrMore(ParseType, state)) {
+  if (ZeroOrMore(ParseOverloadAttribute, state) &&
+      OneOrMore(ParseType, state)) {
     RestoreAppend(state, copy.append);
     MaybeAppend(state, "()");
     return true;
@@ -1372,11 +1767,43 @@ static bool ParseBareFunctionType(State *state) {
   return false;
 }
 
+// <overload-attribute> ::= Ua <name>
+//
+// The nonstandard <overload-attribute> production is sufficient to accept the
+// current implementation of __attribute__((enable_if(condition, "message")))
+// and future attributes of a similar shape.  See
+// https://clang.llvm.org/docs/AttributeReference.html#enable-if and the
+// definition of CXXNameMangler::mangleFunctionEncodingBareType in Clang's
+// source code.
+static bool ParseOverloadAttribute(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  if (ParseTwoCharToken(state, "Ua") && ParseName(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
 // <class-enum-type> ::= <name>
+//                   ::= Ts <name>  # struct Name or class Name
+//                   ::= Tu <name>  # union Name
+//                   ::= Te <name>  # enum Name
+//
+// See http://shortn/_W3YrltiEd0.
 static bool ParseClassEnumType(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
-  return ParseName(state);
+  ParseState copy = state->parse_state;
+  if (Optional(ParseTwoCharToken(state, "Ts") ||
+               ParseTwoCharToken(state, "Tu") ||
+               ParseTwoCharToken(state, "Te")) &&
+      ParseName(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
 }
 
 // <array-type> ::= A <(positive dimension) number> _ <(element) type>
@@ -1413,21 +1840,83 @@ static bool ParsePointerToMemberType(State *state) {
 
 // <template-param> ::= T_
 //                  ::= T <parameter-2 non-negative number> _
+//                  ::= TL <level-1> __
+//                  ::= TL <level-1> _ <parameter-2 non-negative number> _
 static bool ParseTemplateParam(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
   if (ParseTwoCharToken(state, "T_")) {
     MaybeAppend(state, "?");  // We don't support template substitutions.
-    return true;
+    return true;              // ::= T_
   }
 
   ParseState copy = state->parse_state;
   if (ParseOneCharToken(state, 'T') && ParseNumber(state, nullptr) &&
       ParseOneCharToken(state, '_')) {
     MaybeAppend(state, "?");  // We don't support template substitutions.
+    return true;              // ::= T <parameter-2 non-negative number> _
+  }
+  state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "TL") && ParseNumber(state, nullptr)) {
+    if (ParseTwoCharToken(state, "__")) {
+      MaybeAppend(state, "?");  // We don't support template substitutions.
+      return true;              // ::= TL <level-1> __
+    }
+
+    if (ParseOneCharToken(state, '_') && ParseNumber(state, nullptr) &&
+        ParseOneCharToken(state, '_')) {
+      MaybeAppend(state, "?");  // We don't support template substitutions.
+      return true;  // ::= TL <level-1> _ <parameter-2 non-negative number> _
+    }
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// <template-param-decl>
+//   ::= Ty                                  # template type parameter
+//   ::= Tk <concept name> [<template-args>] # constrained type parameter
+//   ::= Tn <type>                           # template non-type parameter
+//   ::= Tt <template-param-decl>* E         # template template parameter
+//   ::= Tp <template-param-decl>            # template parameter pack
+//
+// NOTE: <concept name> is just a <name>: http://shortn/_MqJVyr0fc1
+// TODO(b/324066279): Implement optional suffix for `Tt`:
+// [Q <requires-clause expr>]
+static bool ParseTemplateParamDecl(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+
+  if (ParseTwoCharToken(state, "Ty")) {
     return true;
   }
   state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "Tk") && ParseName(state) &&
+      Optional(ParseTemplateArgs(state))) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "Tn") && ParseType(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "Tt") &&
+      ZeroOrMore(ParseTemplateParamDecl, state) &&
+      ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "Tp") && ParseTemplateParamDecl(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
   return false;
 }
 
@@ -1441,13 +1930,14 @@ static bool ParseTemplateTemplateParam(State *state) {
           ParseSubstitution(state, /*accept_std=*/false));
 }
 
-// <template-args> ::= I <template-arg>+ E
+// <template-args> ::= I <template-arg>+ [Q <requires-clause expr>] E
 static bool ParseTemplateArgs(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
   ParseState copy = state->parse_state;
   DisableAppend(state);
   if (ParseOneCharToken(state, 'I') && OneOrMore(ParseTemplateArg, state) &&
+      Optional(ParseQRequiresClauseExpr(state)) &&
       ParseOneCharToken(state, 'E')) {
     RestoreAppend(state, copy.append);
     MaybeAppend(state, "<>");
@@ -1457,7 +1947,8 @@ static bool ParseTemplateArgs(State *state) {
   return false;
 }
 
-// <template-arg>  ::= <type>
+// <template-arg>  ::= <template-param-decl> <template-arg>
+//                 ::= <type>
 //                 ::= <expr-primary>
 //                 ::= J <template-arg>* E        # argument pack
 //                 ::= X <expression> E
@@ -1541,7 +2032,7 @@ static bool ParseTemplateArg(State *state) {
   //     ::= L <source-name> [<template-args>] [<expr-cast-value> E]
   if (ParseLocalSourceName(state) && Optional(ParseTemplateArgs(state))) {
     copy = state->parse_state;
-    if (ParseExprCastValue(state) && ParseOneCharToken(state, 'E')) {
+    if (ParseExprCastValueAndTrailingE(state)) {
       return true;
     }
     state->parse_state = copy;
@@ -1560,6 +2051,12 @@ static bool ParseTemplateArg(State *state) {
     return true;
   }
   state->parse_state = copy;
+
+  if (ParseTemplateParamDecl(state) && ParseTemplateArg(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
   return false;
 }
 
@@ -1614,6 +2111,13 @@ static bool ParseBaseUnresolvedName(State *state) {
 //                         <base-unresolved-name>
 //                   ::= [gs] sr <unresolved-qualifier-level>+ E
 //                         <base-unresolved-name>
+//                   ::= sr St <simple-id> <simple-id>  # nonstandard
+//
+// The last case is not part of the official grammar but has been observed in
+// real-world examples that the GNU demangler (but not the LLVM demangler) is
+// able to decode; see demangle_test.cc for one such symbol name.  The shape
+// sr St <simple-id> <simple-id> was inferred by closed-box testing of the GNU
+// demangler.
 static bool ParseUnresolvedName(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
@@ -1633,7 +2137,7 @@ static bool ParseUnresolvedName(State *state) {
 
   if (ParseTwoCharToken(state, "sr") && ParseOneCharToken(state, 'N') &&
       ParseUnresolvedType(state) &&
-      OneOrMore(/* <unresolved-qualifier-level> ::= */ ParseSimpleId, state) &&
+      OneOrMore(ParseUnresolvedQualifierLevel, state) &&
       ParseOneCharToken(state, 'E') && ParseBaseUnresolvedName(state)) {
     return true;
   }
@@ -1641,35 +2145,160 @@ static bool ParseUnresolvedName(State *state) {
 
   if (Optional(ParseTwoCharToken(state, "gs")) &&
       ParseTwoCharToken(state, "sr") &&
-      OneOrMore(/* <unresolved-qualifier-level> ::= */ ParseSimpleId, state) &&
+      OneOrMore(ParseUnresolvedQualifierLevel, state) &&
       ParseOneCharToken(state, 'E') && ParseBaseUnresolvedName(state)) {
     return true;
   }
   state->parse_state = copy;
 
+  if (ParseTwoCharToken(state, "sr") && ParseTwoCharToken(state, "St") &&
+      ParseSimpleId(state) && ParseSimpleId(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
   return false;
 }
 
-// <expression> ::= <1-ary operator-name> <expression>
-//              ::= <2-ary operator-name> <expression> <expression>
-//              ::= <3-ary operator-name> <expression> <expression> <expression>
-//              ::= cl <expression>+ E
-//              ::= cp <simple-id> <expression>* E # Clang-specific.
-//              ::= cv <type> <expression>      # type (expression)
-//              ::= cv <type> _ <expression>* E # type (expr-list)
-//              ::= st <type>
-//              ::= <template-param>
-//              ::= <function-param>
-//              ::= <expr-primary>
-//              ::= dt <expression> <unresolved-name> # expr.name
-//              ::= pt <expression> <unresolved-name> # expr->name
-//              ::= sp <expression>         # argument pack expansion
-//              ::= sr <type> <unqualified-name> <template-args>
-//              ::= sr <type> <unqualified-name>
+// <unresolved-qualifier-level> ::= <simple-id>
+//                              ::= <substitution> <template-args>
+//
+// The production <substitution> <template-args> is nonstandard but is observed
+// in practice.  An upstream discussion on the best shape of <unresolved-name>
+// has not converged:
+//
+// https://github.com/itanium-cxx-abi/cxx-abi/issues/38
+static bool ParseUnresolvedQualifierLevel(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+
+  if (ParseSimpleId(state)) return true;
+
+  ParseState copy = state->parse_state;
+  if (ParseSubstitution(state, /*accept_std=*/false) &&
+      ParseTemplateArgs(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// <union-selector> ::= _ [<number>]
+//
+// https://github.com/itanium-cxx-abi/cxx-abi/issues/47
+static bool ParseUnionSelector(State *state) {
+  return ParseOneCharToken(state, '_') && Optional(ParseNumber(state, nullptr));
+}
+
 // <function-param> ::= fp <(top-level) CV-qualifiers> _
 //                  ::= fp <(top-level) CV-qualifiers> <number> _
 //                  ::= fL <number> p <(top-level) CV-qualifiers> _
 //                  ::= fL <number> p <(top-level) CV-qualifiers> <number> _
+//                  ::= fpT  # this
+static bool ParseFunctionParam(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+
+  ParseState copy = state->parse_state;
+
+  // Function-param expression (level 0).
+  if (ParseTwoCharToken(state, "fp") && Optional(ParseCVQualifiers(state)) &&
+      Optional(ParseNumber(state, nullptr)) && ParseOneCharToken(state, '_')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // Function-param expression (level 1+).
+  if (ParseTwoCharToken(state, "fL") && Optional(ParseNumber(state, nullptr)) &&
+      ParseOneCharToken(state, 'p') && Optional(ParseCVQualifiers(state)) &&
+      Optional(ParseNumber(state, nullptr)) && ParseOneCharToken(state, '_')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  return ParseThreeCharToken(state, "fpT");
+}
+
+// <braced-expression> ::= <expression>
+//                     ::= di <field source-name> <braced-expression>
+//                     ::= dx <index expression> <braced-expression>
+//                     ::= dX <expression> <expression> <braced-expression>
+static bool ParseBracedExpression(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+
+  ParseState copy = state->parse_state;
+
+  if (ParseTwoCharToken(state, "di") && ParseSourceName(state) &&
+      ParseBracedExpression(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "dx") && ParseExpression(state) &&
+      ParseBracedExpression(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "dX") &&
+      ParseExpression(state) && ParseExpression(state) &&
+      ParseBracedExpression(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  return ParseExpression(state);
+}
+
+// <expression> ::= <1-ary operator-name> <expression>
+//              ::= <2-ary operator-name> <expression> <expression>
+//              ::= <3-ary operator-name> <expression> <expression> <expression>
+//              ::= pp_ <expression>  # ++e; pp <expression> is e++
+//              ::= mm_ <expression>  # --e; mm <expression> is e--
+//              ::= cl <expression>+ E
+//              ::= cp <simple-id> <expression>* E # Clang-specific.
+//              ::= so <type> <expression> [<number>] <union-selector>* [p] E
+//              ::= cv <type> <expression>      # type (expression)
+//              ::= cv <type> _ <expression>* E # type (expr-list)
+//              ::= tl <type> <braced-expression>* E
+//              ::= il <braced-expression>* E
+//              ::= [gs] nw <expression>* _ <type> E
+//              ::= [gs] nw <expression>* _ <type> <initializer>
+//              ::= [gs] na <expression>* _ <type> E
+//              ::= [gs] na <expression>* _ <type> <initializer>
+//              ::= [gs] dl <expression>
+//              ::= [gs] da <expression>
+//              ::= dc <type> <expression>
+//              ::= sc <type> <expression>
+//              ::= cc <type> <expression>
+//              ::= rc <type> <expression>
+//              ::= ti <type>
+//              ::= te <expression>
+//              ::= st <type>
+//              ::= at <type>
+//              ::= az <expression>
+//              ::= nx <expression>
+//              ::= <template-param>
+//              ::= <function-param>
+//              ::= sZ <template-param>
+//              ::= sZ <function-param>
+//              ::= sP <template-arg>* E
+//              ::= <expr-primary>
+//              ::= dt <expression> <unresolved-name> # expr.name
+//              ::= pt <expression> <unresolved-name> # expr->name
+//              ::= sp <expression>         # argument pack expansion
+//              ::= fl <binary operator-name> <expression>
+//              ::= fr <binary operator-name> <expression>
+//              ::= fL <binary operator-name> <expression> <expression>
+//              ::= fR <binary operator-name> <expression> <expression>
+//              ::= tw <expression>
+//              ::= tr
+//              ::= sr <type> <unqualified-name> <template-args>
+//              ::= sr <type> <unqualified-name>
+//              ::= u <source-name> <template-arg>* E  # vendor extension
+//              ::= rq <requirement>+ E
+//              ::= rQ <bare-function-type> _ <requirement>+ E
 static bool ParseExpression(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
@@ -1686,6 +2315,15 @@ static bool ParseExpression(State *state) {
   }
   state->parse_state = copy;
 
+  // Preincrement and predecrement.  Postincrement and postdecrement are handled
+  // by the operator-name logic later on.
+  if ((ParseThreeCharToken(state, "pp_") ||
+       ParseThreeCharToken(state, "mm_")) &&
+      ParseExpression(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
   // Clang-specific "cp <simple-id> <expression>* E"
   //   https://clang.llvm.org/doxygen/ItaniumMangle_8cpp_source.html#l04338
   if (ParseTwoCharToken(state, "cp") && ParseSimpleId(state) &&
@@ -1694,17 +2332,65 @@ static bool ParseExpression(State *state) {
   }
   state->parse_state = copy;
 
-  // Function-param expression (level 0).
-  if (ParseTwoCharToken(state, "fp") && Optional(ParseCVQualifiers(state)) &&
-      Optional(ParseNumber(state, nullptr)) && ParseOneCharToken(state, '_')) {
+  // <expression> ::= so <type> <expression> [<number>] <union-selector>* [p] E
+  //
+  // https://github.com/itanium-cxx-abi/cxx-abi/issues/47
+  if (ParseTwoCharToken(state, "so") && ParseType(state) &&
+      ParseExpression(state) && Optional(ParseNumber(state, nullptr)) &&
+      ZeroOrMore(ParseUnionSelector, state) &&
+      Optional(ParseOneCharToken(state, 'p')) &&
+      ParseOneCharToken(state, 'E')) {
     return true;
   }
   state->parse_state = copy;
 
-  // Function-param expression (level 1+).
-  if (ParseTwoCharToken(state, "fL") && Optional(ParseNumber(state, nullptr)) &&
-      ParseOneCharToken(state, 'p') && Optional(ParseCVQualifiers(state)) &&
-      Optional(ParseNumber(state, nullptr)) && ParseOneCharToken(state, '_')) {
+  // <expression> ::= <function-param>
+  if (ParseFunctionParam(state)) return true;
+  state->parse_state = copy;
+
+  // <expression> ::= tl <type> <braced-expression>* E
+  if (ParseTwoCharToken(state, "tl") && ParseType(state) &&
+      ZeroOrMore(ParseBracedExpression, state) &&
+      ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // <expression> ::= il <braced-expression>* E
+  if (ParseTwoCharToken(state, "il") &&
+      ZeroOrMore(ParseBracedExpression, state) &&
+      ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // <expression> ::= [gs] nw <expression>* _ <type> E
+  //              ::= [gs] nw <expression>* _ <type> <initializer>
+  //              ::= [gs] na <expression>* _ <type> E
+  //              ::= [gs] na <expression>* _ <type> <initializer>
+  if (Optional(ParseTwoCharToken(state, "gs")) &&
+      (ParseTwoCharToken(state, "nw") || ParseTwoCharToken(state, "na")) &&
+      ZeroOrMore(ParseExpression, state) && ParseOneCharToken(state, '_') &&
+      ParseType(state) &&
+      (ParseOneCharToken(state, 'E') || ParseInitializer(state))) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // <expression> ::= [gs] dl <expression>
+  //              ::= [gs] da <expression>
+  if (Optional(ParseTwoCharToken(state, "gs")) &&
+      (ParseTwoCharToken(state, "dl") || ParseTwoCharToken(state, "da")) &&
+      ParseExpression(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // dynamic_cast, static_cast, const_cast, reinterpret_cast.
+  //
+  // <expression> ::= (dc | sc | cc | rc) <type> <expression>
+  if (ParseCharClass(state, "dscr") && ParseOneCharToken(state, 'c') &&
+      ParseType(state) && ParseExpression(state)) {
     return true;
   }
   state->parse_state = copy;
@@ -1746,15 +2432,96 @@ static bool ParseExpression(State *state) {
   }
   state->parse_state = copy;
 
+  // typeid(type)
+  if (ParseTwoCharToken(state, "ti") && ParseType(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // typeid(expression)
+  if (ParseTwoCharToken(state, "te") && ParseExpression(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
   // sizeof type
   if (ParseTwoCharToken(state, "st") && ParseType(state)) {
     return true;
   }
   state->parse_state = copy;
 
+  // alignof(type)
+  if (ParseTwoCharToken(state, "at") && ParseType(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // alignof(expression), a GNU extension
+  if (ParseTwoCharToken(state, "az") && ParseExpression(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // noexcept(expression) appearing as an expression in a dependent signature
+  if (ParseTwoCharToken(state, "nx") && ParseExpression(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // sizeof...(pack)
+  //
+  // <expression> ::= sZ <template-param>
+  //              ::= sZ <function-param>
+  if (ParseTwoCharToken(state, "sZ") &&
+      (ParseFunctionParam(state) || ParseTemplateParam(state))) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // sizeof...(pack) captured from an alias template
+  //
+  // <expression> ::= sP <template-arg>* E
+  if (ParseTwoCharToken(state, "sP") && ZeroOrMore(ParseTemplateArg, state) &&
+      ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // Unary folds (... op pack) and (pack op ...).
+  //
+  // <expression> ::= fl <binary operator-name> <expression>
+  //              ::= fr <binary operator-name> <expression>
+  if ((ParseTwoCharToken(state, "fl") || ParseTwoCharToken(state, "fr")) &&
+      ParseOperatorName(state, nullptr) && ParseExpression(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // Binary folds (init op ... op pack) and (pack op ... op init).
+  //
+  // <expression> ::= fL <binary operator-name> <expression> <expression>
+  //              ::= fR <binary operator-name> <expression> <expression>
+  if ((ParseTwoCharToken(state, "fL") || ParseTwoCharToken(state, "fR")) &&
+      ParseOperatorName(state, nullptr) && ParseExpression(state) &&
+      ParseExpression(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // tw <expression>: throw e
+  if (ParseTwoCharToken(state, "tw") && ParseExpression(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // tr: throw (rethrows an exception from the handler that caught it)
+  if (ParseTwoCharToken(state, "tr")) return true;
+
   // Object and pointer member access expressions.
+  //
+  // <expression> ::= (dt | pt) <expression> <unresolved-name>
   if ((ParseTwoCharToken(state, "dt") || ParseTwoCharToken(state, "pt")) &&
-      ParseExpression(state) && ParseType(state)) {
+      ParseExpression(state) && ParseUnresolvedName(state)) {
     return true;
   }
   state->parse_state = copy;
@@ -1774,9 +2541,61 @@ static bool ParseExpression(State *state) {
   }
   state->parse_state = copy;
 
+  // Vendor extended expressions
+  if (ParseOneCharToken(state, 'u') && ParseSourceName(state) &&
+      ZeroOrMore(ParseTemplateArg, state) && ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // <expression> ::= rq <requirement>+ E
+  //
+  // https://github.com/itanium-cxx-abi/cxx-abi/issues/24
+  if (ParseTwoCharToken(state, "rq") && OneOrMore(ParseRequirement, state) &&
+      ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // <expression> ::= rQ <bare-function-type> _ <requirement>+ E
+  //
+  // https://github.com/itanium-cxx-abi/cxx-abi/issues/24
+  if (ParseTwoCharToken(state, "rQ") && ParseBareFunctionType(state) &&
+      ParseOneCharToken(state, '_') && OneOrMore(ParseRequirement, state) &&
+      ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+
   return ParseUnresolvedName(state);
 }
 
+// <initializer> ::= pi <expression>* E
+//               ::= il <braced-expression>* E
+//
+// The il ... E form is not in the ABI spec but is seen in practice for
+// braced-init-lists in new-expressions, which are standard syntax from C++11
+// on.
+static bool ParseInitializer(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+
+  if (ParseTwoCharToken(state, "pi") && ZeroOrMore(ParseExpression, state) &&
+      ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "il") &&
+      ZeroOrMore(ParseBracedExpression, state) &&
+      ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
 // <expr-primary> ::= L <type> <(value) number> E
 //                ::= L <type> <(value) float> E
 //                ::= L <mangled-name> E
@@ -1819,10 +2638,35 @@ static bool ParseExprPrimary(State *state) {
     return false;
   }
 
-  // The merged cast production.
-  if (ParseOneCharToken(state, 'L') && ParseType(state) &&
-      ParseExprCastValue(state)) {
-    return true;
+  if (ParseOneCharToken(state, 'L')) {
+    // There are two special cases in which a literal may or must contain a type
+    // without a value.  The first is that both LDnE and LDn0E are valid
+    // encodings of nullptr, used in different situations.  Recognize LDnE here,
+    // leaving LDn0E to be recognized by the general logic afterward.
+    if (ParseThreeCharToken(state, "DnE")) return true;
+
+    // The second special case is a string literal, currently mangled in C++98
+    // style as LA<length + 1>_KcE.  This is inadequate to support C++11 and
+    // later versions, and the discussion of this problem has not converged.
+    //
+    // https://github.com/itanium-cxx-abi/cxx-abi/issues/64
+    //
+    // For now the bare-type mangling is what's used in practice, so we
+    // recognize this form and only this form if an array type appears here.
+    // Someday we'll probably have to accept a new form of value mangling in
+    // LA...E constructs.  (Note also that C++20 allows a wide range of
+    // class-type objects as template arguments, so someday their values will be
+    // mangled and we'll have to recognize them here too.)
+    if (RemainingInput(state)[0] == 'A' /* an array type follows */) {
+      if (ParseType(state) && ParseOneCharToken(state, 'E')) return true;
+      state->parse_state = copy;
+      return false;
+    }
+
+    // The merged cast production.
+    if (ParseType(state) && ParseExprCastValueAndTrailingE(state)) {
+      return true;
+    }
   }
   state->parse_state = copy;
 
@@ -1836,7 +2680,7 @@ static bool ParseExprPrimary(State *state) {
 }
 
 // <number> or <float>, followed by 'E', as described above ParseExprPrimary.
-static bool ParseExprCastValue(State *state) {
+static bool ParseExprCastValueAndTrailingE(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
   // We have to be able to backtrack after accepting a number because we could
@@ -1848,39 +2692,148 @@ static bool ParseExprCastValue(State *state) {
   }
   state->parse_state = copy;
 
-  if (ParseFloatNumber(state) && ParseOneCharToken(state, 'E')) {
-    return true;
+  if (ParseFloatNumber(state)) {
+    // <float> for ordinary floating-point types
+    if (ParseOneCharToken(state, 'E')) return true;
+
+    // <float> _ <float> for complex floating-point types
+    if (ParseOneCharToken(state, '_') && ParseFloatNumber(state) &&
+        ParseOneCharToken(state, 'E')) {
+      return true;
+    }
   }
   state->parse_state = copy;
 
   return false;
 }
 
+// Parses `Q <requires-clause expr>`.
+// If parsing fails, applies backtracking to `state`.
+//
+// This function covers two symbols instead of one for convenience,
+// because in LLVM's Itanium ABI mangling grammar, <requires-clause expr>
+// always appears after Q.
+//
+// Does not emit the parsed `requires` clause to simplify the implementation.
+// In other words, these two functions' mangled names will demangle identically:
+//
+// template <typename T>
+// int foo(T) requires IsIntegral<T>;
+//
+// vs.
+//
+// template <typename T>
+// int foo(T);
+static bool ParseQRequiresClauseExpr(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  DisableAppend(state);
+
+  // <requires-clause expr> is just an <expression>: http://shortn/_9E1Ul0rIM8
+  if (ParseOneCharToken(state, 'Q') && ParseExpression(state)) {
+    RestoreAppend(state, copy.append);
+    return true;
+  }
+
+  // also restores append
+  state->parse_state = copy;
+  return false;
+}
+
+// <requirement> ::= X <expression> [N] [R <type-constraint>]
+// <requirement> ::= T <type>
+// <requirement> ::= Q <constraint-expression>
+//
+// <constraint-expression> ::= <expression>
+//
+// https://github.com/itanium-cxx-abi/cxx-abi/issues/24
+static bool ParseRequirement(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+
+  ParseState copy = state->parse_state;
+
+  if (ParseOneCharToken(state, 'X') && ParseExpression(state) &&
+      Optional(ParseOneCharToken(state, 'N')) &&
+      // This logic backtracks cleanly if we eat an R but a valid type doesn't
+      // follow it.
+      (!ParseOneCharToken(state, 'R') || ParseTypeConstraint(state))) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseOneCharToken(state, 'T') && ParseType(state)) return true;
+  state->parse_state = copy;
+
+  if (ParseOneCharToken(state, 'Q') && ParseExpression(state)) return true;
+  state->parse_state = copy;
+
+  return false;
+}
+
+// <type-constraint> ::= <name>
+static bool ParseTypeConstraint(State *state) {
+  return ParseName(state);
+}
+
 // <local-name> ::= Z <(function) encoding> E <(entity) name> [<discriminator>]
 //              ::= Z <(function) encoding> E s [<discriminator>]
+//              ::= Z <(function) encoding> E d [<(parameter) number>] _ <name>
 //
 // Parsing a common prefix of these two productions together avoids an
 // exponential blowup of backtracking.  Parse like:
 //   <local-name> := Z <encoding> E <local-name-suffix>
 //   <local-name-suffix> ::= s [<discriminator>]
+//                       ::= d [<(parameter) number>] _ <name>
 //                       ::= <name> [<discriminator>]
 
 static bool ParseLocalNameSuffix(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
 
+  // <local-name-suffix> ::= d [<(parameter) number>] _ <name>
+  if (ParseOneCharToken(state, 'd') &&
+      (IsDigit(RemainingInput(state)[0]) || RemainingInput(state)[0] == '_')) {
+    int number = -1;
+    Optional(ParseNumber(state, &number));
+    if (number < -1 || number > 2147483645) {
+      // Work around overflow cases.  We do not expect these outside of a fuzzer
+      // or other source of adversarial input.  If we do detect overflow here,
+      // we'll print {default arg#1}.
+      number = -1;
+    }
+    number += 2;
+
+    // The ::{default arg#1}:: infix must be rendered before the lambda itself,
+    // so print this before parsing the rest of the <local-name-suffix>.
+    MaybeAppend(state, "::{default arg#");
+    MaybeAppendDecimal(state, number);
+    MaybeAppend(state, "}::");
+    if (ParseOneCharToken(state, '_') && ParseName(state)) return true;
+
+    // On late parse failure, roll back not only the input but also the output,
+    // whose trailing NUL was overwritten.
+    state->parse_state = copy;
+    if (state->parse_state.append) {
+      state->out[state->parse_state.out_cur_idx] = '\0';
+    }
+    return false;
+  }
+  state->parse_state = copy;
+
+  // <local-name-suffix> ::= <name> [<discriminator>]
   if (MaybeAppend(state, "::") && ParseName(state) &&
       Optional(ParseDiscriminator(state))) {
     return true;
   }
-
-  // Since we're not going to overwrite the above "::" by re-parsing the
-  // <encoding> (whose trailing '\0' byte was in the byte now holding the
-  // first ':'), we have to rollback the "::" if the <name> parse failed.
+  state->parse_state = copy;
   if (state->parse_state.append) {
-    state->out[state->parse_state.out_cur_idx - 2] = '\0';
+    state->out[state->parse_state.out_cur_idx] = '\0';
   }
 
+  // <local-name-suffix> ::= s [<discriminator>]
   return ParseOneCharToken(state, 's') && Optional(ParseDiscriminator(state));
 }
 
@@ -1896,12 +2849,22 @@ static bool ParseLocalName(State *state) {
   return false;
 }
 
-// <discriminator> := _ <(non-negative) number>
+// <discriminator> := _ <digit>
+//                 := __ <number (>= 10)> _
 static bool ParseDiscriminator(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
   ParseState copy = state->parse_state;
-  if (ParseOneCharToken(state, '_') && ParseNumber(state, nullptr)) {
+
+  // Both forms start with _ so parse that first.
+  if (!ParseOneCharToken(state, '_')) return false;
+
+  // <digit>
+  if (ParseDigit(state, nullptr)) return true;
+
+  // _ <number> _
+  if (ParseOneCharToken(state, '_') && ParseNumber(state, nullptr) &&
+      ParseOneCharToken(state, '_')) {
     return true;
   }
   state->parse_state = copy;
@@ -1947,6 +2910,7 @@ static bool ParseSubstitution(State *state, bool accept_std) {
           MaybeAppend(state, p->real_name);
         }
         ++state->parse_state.mangled_idx;
+        UpdateHighWaterMark(state);
         return true;
       }
     }
@@ -1972,10 +2936,13 @@ static bool ParseTopLevelMangledName(State *state) {
         MaybeAppend(state, RemainingInput(state));
         return true;
       }
+      ReportHighWaterMark(state);
       return false;  // Unconsumed suffix.
     }
     return true;
   }
+
+  ReportHighWaterMark(state);
   return false;
 }
 
@@ -1985,6 +2952,10 @@ static bool Overflowed(const State *state) {
 
 // The demangler entry point.
 bool Demangle(const char* mangled, char* out, size_t out_size) {
+  if (mangled[0] == '_' && mangled[1] == 'R') {
+    return DemangleRustSymbolEncoding(mangled, out, out_size);
+  }
+
   State state;
   InitState(&state, mangled, out, out_size);
   return ParseTopLevelMangledName(&state) && !Overflowed(&state) &&