Try not to lose easy type combinators in S::operator const int*() and the like.

PiperOrigin-RevId: 641411131
Change-Id: Icba1307cccb8957e09f087a7b544f7fe8bfd8333

2 files changed, 139 insertions, 6 deletions

diff --git a/absl/debugging/internal/demangle.cc b/absl/debugging/internal/demangle.cc
index 7ae21dcb..d97dfad4 100644
--- a/absl/debugging/internal/demangle.cc
+++ b/absl/debugging/internal/demangle.cc
@@ -589,6 +589,7 @@ 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);
@@ -1056,7 +1057,7 @@ 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;
@@ -1105,6 +1106,65 @@ static bool ParseOperatorName(State *state, int *arity) {
   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>
@@ -1442,12 +1502,18 @@ static bool ParseExtendedQualifier(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
   ParseState copy = state->parse_state;
-  if (ParseOneCharToken(state, 'U') && ParseSourceName(state) &&
-      Optional(ParseTemplateArgs(state))) {
-    return true;
+
+  if (!ParseOneCharToken(state, 'U')) return false;
+
+  bool append = state->parse_state.append;
+  DisableAppend(state);
+  if (!ParseSourceName(state)) {
+    state->parse_state = copy;
+    return false;
   }
-  state->parse_state = copy;
-  return false;
+  Optional(ParseTemplateArgs(state));
+  RestoreAppend(state, append);
+  return true;
 }
 
 // <builtin-type> ::= v, etc.  # single-character builtin types
diff --git a/absl/debugging/internal/demangle_test.cc b/absl/debugging/internal/demangle_test.cc
index 2b58d39b..1b305f74 100644
--- a/absl/debugging/internal/demangle_test.cc
+++ b/absl/debugging/internal/demangle_test.cc
@@ -708,6 +708,73 @@ TEST(Demangle, DependentBitInt) {
   EXPECT_STREQ("S::operator _BitInt(?)<>()", tmp);
 }
 
+TEST(Demangle, ConversionToPointerType) {
+  char tmp[80];
+
+  // S::operator int*() const
+  EXPECT_TRUE(Demangle("_ZNK1ScvPiEv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("S::operator int*()", tmp);
+}
+
+TEST(Demangle, ConversionToLvalueReferenceType) {
+  char tmp[80];
+
+  // S::operator int&() const
+  EXPECT_TRUE(Demangle("_ZNK1ScvRiEv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("S::operator int&()", tmp);
+}
+
+TEST(Demangle, ConversionToRvalueReferenceType) {
+  char tmp[80];
+
+  // S::operator int&&() const
+  EXPECT_TRUE(Demangle("_ZNK1ScvOiEv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("S::operator int&&()", tmp);
+}
+
+TEST(Demangle, ConversionToComplexFloatingPointType) {
+  char tmp[80];
+
+  // S::operator float _Complex() const
+  EXPECT_TRUE(Demangle("_ZNK1ScvCfEv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("S::operator float _Complex()", tmp);
+}
+
+TEST(Demangle, ConversionToImaginaryFloatingPointType) {
+  char tmp[80];
+
+  // S::operator float _Imaginary() const
+  EXPECT_TRUE(Demangle("_ZNK1ScvGfEv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("S::operator float _Imaginary()", tmp);
+}
+
+TEST(Demangle, ConversionToPointerToCvQualifiedType) {
+  char tmp[80];
+
+  // S::operator int const volatile restrict*() const
+  EXPECT_TRUE(Demangle("_ZNK1ScvPrVKiEv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("S::operator int const volatile restrict*()", tmp);
+}
+
+TEST(Demangle, ConversionToLayeredPointerType) {
+  char tmp[80];
+
+  // S::operator int const* const*() const
+  EXPECT_TRUE(Demangle("_ZNK1ScvPKPKiEv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("S::operator int const* const*()", tmp);
+}
+
+TEST(Demangle, ConversionToTypeWithExtendedQualifier) {
+  char tmp[80];
+
+  // S::operator int const AS128*() const
+  //
+  // Because our scan of easy type constructors stops at the extended qualifier,
+  // the demangling preserves the * but loses the const.
+  EXPECT_TRUE(Demangle("_ZNK1ScvPU5AS128KiEv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("S::operator int*()", tmp);
+}
+
 TEST(Demangle, GlobalInitializers) {
   char tmp[80];