Demangle C++ so ... E encodings (typically array-to-pointer decay).

PiperOrigin-RevId: 636566755
Change-Id: I2c8c1f19a67a7a487dd2bbb46c17f9fb4e2b037c

absl/debugging/internal/demangle.cc

@@ -578,6 +578,7 @@ static bool ParseTemplateArgs(State *state);
 static bool ParseTemplateArg(State *state);
 static bool ParseBaseUnresolvedName(State *state);
 static bool ParseUnresolvedName(State *state);
+static bool ParseUnionSelector(State* state);
 static bool ParseExpression(State *state);
 static bool ParseExprPrimary(State *state);
 static bool ParseExprCastValue(State *state);
@@ -1743,11 +1744,19 @@ static bool ParseUnresolvedName(State *state) {
   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));
+}
+
 // <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.
+//              ::= so <type> <expression> [<number>] <union-selector>* [p] E
 //              ::= cv <type> <expression>      # type (expression)
 //              ::= cv <type> _ <expression>* E # type (expr-list)
 //              ::= st <type>
@@ -1787,6 +1796,18 @@ static bool ParseExpression(State *state) {
   }
   state->parse_state = copy;
 
+  // <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 0).
   if (ParseTwoCharToken(state, "fp") && Optional(ParseCVQualifiers(state)) &&
       Optional(ParseNumber(state, nullptr)) && ParseOneCharToken(state, '_')) {

absl/debugging/internal/demangle_test.cc

@@ -300,6 +300,35 @@ TEST(Demangle, AbiTags) {
   EXPECT_STREQ("C[abi:bar][abi:foo]()", tmp);
 }
 
+// Test subobject-address template parameters.
+TEST(Demangle, SubobjectAddresses) {
+  char tmp[80];
+
+  // void f<a.<char const at offset 123>>()
+  EXPECT_TRUE(Demangle("_Z1fIXsoKcL_Z1aE123EEEvv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+
+  // void f<&a.<char const at offset 0>>()
+  EXPECT_TRUE(Demangle("_Z1fIXadsoKcL_Z1aEEEEvv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+
+  // void f<&a.<char const at offset 123>>()
+  EXPECT_TRUE(Demangle("_Z1fIXadsoKcL_Z1aE123EEEvv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+
+  // void f<&a.<char const at offset 123>>(), past the end this time
+  EXPECT_TRUE(Demangle("_Z1fIXadsoKcL_Z1aE123pEEEvv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+
+  // void f<&a.<char const at offset 0>>() with union-selectors
+  EXPECT_TRUE(Demangle("_Z1fIXadsoKcL_Z1aE__1_234EEEvv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+
+  // void f<&a.<char const at offset 123>>(), past the end, with union-selector
+  EXPECT_TRUE(Demangle("_Z1fIXadsoKcL_Z1aE123_456pEEEvv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+}
+
 // Test one Rust symbol to exercise Demangle's delegation path.  Rust demangling
 // itself is more thoroughly tested in demangle_rust_test.cc.
 TEST(Demangle, DelegatesToDemangleRustSymbolEncoding) {