Recognize C++ vendor extended expressions (e.g., u9__is_same...E).

PiperOrigin-RevId: 636911360
Change-Id: I525e25b90b91712b95ab7499425de85610ff9115

absl/debugging/internal/demangle.cc

diff --git a/absl/debugging/internal/demangle.cc b/absl/debugging/internal/demangle.cc
index 72462ee..6012a59 100644
--- a/absl/debugging/internal/demangle.cc
+++ b/absl/debugging/internal/demangle.cc
@@ -1851,6 +1851,7 @@
 //              ::= sp <expression>         # argument pack expansion
 //              ::= sr <type> <unqualified-name> <template-args>
 //              ::= sr <type> <unqualified-name>
+//              ::= u <source-name> <template-arg>* E  # vendor extension
 static bool ParseExpression(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
@@ -1974,6 +1975,13 @@
   }
   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;
+
   return ParseUnresolvedName(state);
 }
 

absl/debugging/internal/demangle_test.cc

diff --git a/absl/debugging/internal/demangle_test.cc b/absl/debugging/internal/demangle_test.cc
index 8dcfb51..51e3664 100644
--- a/absl/debugging/internal/demangle_test.cc
+++ b/absl/debugging/internal/demangle_test.cc
@@ -387,6 +387,18 @@
   EXPECT_STREQ("g<>()", tmp);
 }
 
+TEST(Demangle, VendorExtendedExpressions) {
+  char tmp[80];
+
+  // void f<__e()>()
+  EXPECT_TRUE(Demangle("_Z1fIXu3__eEEEvv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+
+  // void f<__e(int, long)>()
+  EXPECT_TRUE(Demangle("_Z1fIXu3__eilEEEvv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+}
+
 TEST(Demangle, DirectListInitialization) {
   char tmp[80];