From abc0f8d1096a66c087365327c217963eab15839c Mon Sep 17 00:00:00 2001
From: Chris Mihelich <cmihelic@google.com>
Date: Wed, 29 May 2024 05:05:20 -0700
Subject: Demangle Clang's encoding of __attribute__((enable_if(condition,
 "message"))).

PiperOrigin-RevId: 638244694
Change-Id: I80393c6c00f1554057a915e0d71f88b7d899818c
---
 absl/debugging/internal/demangle.cc | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

(limited to 'absl/debugging/internal/demangle.cc')

diff --git a/absl/debugging/internal/demangle.cc b/absl/debugging/internal/demangle.cc
index f04e4dbc..606ff4e7 100644
--- a/absl/debugging/internal/demangle.cc
+++ b/absl/debugging/internal/demangle.cc
@@ -585,6 +585,7 @@ static bool ParseCVQualifiers(State *state);
 static bool ParseBuiltinType(State *state);
 static bool ParseFunctionType(State *state);
 static bool ParseBareFunctionType(State *state);
+static bool ParseOverloadAttribute(State *state);
 static bool ParseClassEnumType(State *state);
 static bool ParseArrayType(State *state);
 static bool ParsePointerToMemberType(State *state);
@@ -1437,13 +1438,17 @@ static bool ParseFunctionType(State *state) {
   return true;
 }
 
-// <bare-function-type> ::= <(signature) type>+
+// <bare-function-type> ::= <overload-attribute>* <(signature) type>+
+//
+// The <overload-attribute>* prefix is nonstandard; see the comment on
+// ParseOverloadAttribute.
 static bool ParseBareFunctionType(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
   ParseState copy = state->parse_state;
   DisableAppend(state);
-  if (OneOrMore(ParseType, state)) {
+  if (ZeroOrMore(ParseOverloadAttribute, state) &&
+      OneOrMore(ParseType, state)) {
     RestoreAppend(state, copy.append);
     MaybeAppend(state, "()");
     return true;
@@ -1452,6 +1457,25 @@ static bool ParseBareFunctionType(State *state) {
   return false;
 }
 
+// <overload-attribute> ::= Ua <name>
+//
+// The nonstandard <overload-attribute> production is sufficient to accept the
+// current implementation of __attribute__((enable_if(condition, "message")))
+// and future attributes of a similar shape.  See
+// https://clang.llvm.org/docs/AttributeReference.html#enable-if and the
+// definition of CXXNameMangler::mangleFunctionEncodingBareType in Clang's
+// source code.
+static bool ParseOverloadAttribute(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  if (ParseTwoCharToken(state, "Ua") && ParseName(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
 // <class-enum-type> ::= <name>
 static bool ParseClassEnumType(State *state) {
   ComplexityGuard guard(state);
-- 
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