Demangle alignof expressions, at... and az....

PiperOrigin-RevId: 640568425
Change-Id: Id63142ff2e94d7f7ee16367f34a2e4ae81c29b4e

absl/debugging/internal/demangle.cc

@@ -1996,6 +1996,8 @@ static bool ParseBracedExpression(State *state) {
 //              ::= cc <type> <expression>
 //              ::= rc <type> <expression>
 //              ::= st <type>
+//              ::= at <type>
+//              ::= az <expression>
 //              ::= <template-param>
 //              ::= <function-param>
 //              ::= sZ <template-param>
@@ -2122,6 +2124,18 @@ static bool ParseExpression(State *state) {
   }
   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;
+
   // sizeof...(pack)
   //
   // <expression> ::= sZ <template-param>

absl/debugging/internal/demangle_test.cc

@@ -1098,6 +1098,36 @@ TEST(Demangle, ReinterpretCast) {
   EXPECT_STREQ("f<>()", tmp);
 }
 
+TEST(Demangle, AlignofType) {
+  char tmp[80];
+
+  // Source:
+  //
+  // template <class T> T f(T (&a)[alignof(T)]) { return a[0]; }
+  // template int f<int>(int (&)[alignof(int)]);
+  //
+  // Full LLVM demangling of the instantiation of f:
+  //
+  // int f<int>(int (&) [alignof (int)])
+  EXPECT_TRUE(Demangle("_Z1fIiET_RAatS0__S0_", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+}
+
+TEST(Demangle, AlignofExpression) {
+  char tmp[80];
+
+  // Source (note that this uses a GNU extension; it is not standard C++):
+  //
+  // template <class T> T f(T (&a)[alignof(T{})]) { return a[0]; }
+  // template int f<int>(int (&)[alignof(int{})]);
+  //
+  // Full LLVM demangling of the instantiation of f:
+  //
+  // int f<int>(int (&) [alignof (int{})])
+  EXPECT_TRUE(Demangle("_Z1fIiET_RAaztlS0_E_S0_", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+}
+
 TEST(Demangle, ThreadLocalWrappers) {
   char tmp[80];