Support [[gnu::abi_tag("xyz")]] demangling.

PiperOrigin-RevId: 460752575
Change-Id: I9629504b5c63dbfe367cd55e287a782cd8fa546c

absl/debugging/internal/demangle.cc

@@ -548,6 +548,7 @@ static bool ParseSpecialName(State *state);
 static bool ParseCallOffset(State *state);
 static bool ParseNVOffset(State *state);
 static bool ParseVOffset(State *state);
+static bool ParseAbiTags(State *state);
 static bool ParseCtorDtorName(State *state);
 static bool ParseDecltype(State *state);
 static bool ParseType(State *state);
@@ -601,7 +602,7 @@ static bool ParseSubstitution(State *state, bool accept_std);
 //
 // Reference:
 // - Itanium C++ ABI
-//   <https://mentorembedded.github.io/cxx-abi/abi.html#mangling>
+//   <https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling>
 
 // <mangled-name> ::= _Z <encoding>
 static bool ParseMangledName(State *state) {
@@ -741,17 +742,42 @@ static bool ParsePrefix(State *state) {
   return true;
 }
 
-// <unqualified-name> ::= <operator-name>
-//                    ::= <ctor-dtor-name>
-//                    ::= <source-name>
-//                    ::= <local-source-name> // GCC extension; see below.
-//                    ::= <unnamed-type-name>
+// <unqualified-name> ::= <operator-name> [<abi-tags>]
+//                    ::= <ctor-dtor-name> [<abi-tags>]
+//                    ::= <source-name> [<abi-tags>]
+//                    ::= <local-source-name> [<abi-tags>]
+//                    ::= <unnamed-type-name> [<abi-tags>]
+//
+// <local-source-name> is a GCC extension; see below.
 static bool ParseUnqualifiedName(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
-  return (ParseOperatorName(state, nullptr) || ParseCtorDtorName(state) ||
-          ParseSourceName(state) || ParseLocalSourceName(state) ||
-          ParseUnnamedTypeName(state));
+  if (ParseOperatorName(state, nullptr) || ParseCtorDtorName(state) ||
+      ParseSourceName(state) || ParseLocalSourceName(state) ||
+      ParseUnnamedTypeName(state)) {
+    return ParseAbiTags(state);
+  }
+  return false;
+}
+
+// <abi-tags> ::= <abi-tag> [<abi-tags>]
+// <abi-tag>  ::= B <source-name>
+static bool ParseAbiTags(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+
+  while (ParseOneCharToken(state, 'B')) {
+    ParseState copy = state->parse_state;
+    MaybeAppend(state, "[abi:");
+
+    if (!ParseSourceName(state)) {
+      state->parse_state = copy;
+      return false;
+    }
+    MaybeAppend(state, "]");
+  }
+
+  return true;
 }
 
 // <source-name> ::= <positive length number> <identifier>

absl/debugging/internal/demangle_test.cc

@@ -102,6 +102,30 @@ TEST(Demangle, Clones) {
   EXPECT_FALSE(Demangle("_ZL3Foov.isra.2.constprop.", tmp, sizeof(tmp)));
 }
 
+// Test the GNU abi_tag extension.
+TEST(Demangle, AbiTags) {
+  char tmp[80];
+
+  // Mangled name generated via:
+  // struct [[gnu::abi_tag("abc")]] A{};
+  // A a;
+  EXPECT_TRUE(Demangle("_Z1aB3abc", tmp, sizeof(tmp)));
+  EXPECT_STREQ("a[abi:abc]", tmp);
+
+  // Mangled name generated via:
+  // struct B {
+  //   B [[gnu::abi_tag("xyz")]] (){};
+  // };
+  // B b;
+  EXPECT_TRUE(Demangle("_ZN1BC2B3xyzEv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("B::B[abi:xyz]()", tmp);
+
+  // Mangled name generated via:
+  // [[gnu::abi_tag("foo", "bar")]] void C() {}
+  EXPECT_TRUE(Demangle("_Z1CB3barB3foov", tmp, sizeof(tmp)));
+  EXPECT_STREQ("C[abi:bar][abi:foo]()", tmp);
+}
+
 // Tests that verify that Demangle footprint is within some limit.
 // They are not to be run under sanitizers as the sanitizers increase
 // stack consumption by about 4x.