Demangle complex floating-point literals.

PiperOrigin-RevId: 641324572
Change-Id: Ie266da9c8c702e62b89352d64870fb41d2ea76c3

absl/debugging/internal/demangle.cc

@@ -2476,8 +2476,15 @@ static bool ParseExprCastValueAndTrailingE(State *state) {
   }
   state->parse_state = copy;
 
-  if (ParseFloatNumber(state) && ParseOneCharToken(state, 'E')) {
-    return true;
+  if (ParseFloatNumber(state)) {
+    // <float> for ordinary floating-point types
+    if (ParseOneCharToken(state, 'E')) return true;
+
+    // <float> _ <float> for complex floating-point types
+    if (ParseOneCharToken(state, '_') && ParseFloatNumber(state) &&
+        ParseOneCharToken(state, 'E')) {
+      return true;
+    }
   }
   state->parse_state = copy;
 

absl/debugging/internal/demangle_test.cc

@@ -641,6 +641,25 @@ TEST(Demangle, StringLiterals) {
   EXPECT_STREQ("f<>()", tmp);
 }
 
+TEST(Demangle, ComplexFloatingPointLiterals) {
+  char tmp[80];
+
+  // Source (use g++ -fext-numeric-literals to compile):
+  //
+  // using C = double _Complex;
+  // template <class T> void f(char (&)[sizeof(C{sizeof(T)} + 4.0j)]) {}
+  // template void f<int>(char (&)[sizeof(C{sizeof(int)} + 4.0j)]);
+  //
+  // GNU demangling:
+  //
+  // void f<int>(char (&) [sizeof (double _Complex{sizeof (int)}+
+  // ((double _Complex)0000000000000000_4010000000000000))])
+  EXPECT_TRUE(Demangle(
+      "_Z1fIiEvRAszpltlCdstT_ELS0_0000000000000000_4010000000000000E_c",
+      tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+}
+
 TEST(Demangle, GlobalInitializers) {
   char tmp[80];