From 7fcb278d1e5b18d8c56588ad08bfb5d7a70303e1 Mon Sep 17 00:00:00 2001
From: Thomas Anderson <thomasanderson@google.com>
Date: Sun, 6 Jan 2019 22:26:08 -0800
Subject: [PATCH] Fix demangling template parameter packs (#414)

* Fix demangling template parameter packs

Clang 4.0.1-10 and gcc 7.3.0 both mangle the function "void add<int>(int)" as
"_Z3addIJiEEvDpT_".  The template parameter pack is of the form
J <template-arg>* E

The opening character for a param pack could be either I or J, as libiberty
follows [1].  This change simply adds the J case.

[1] https://github.com/gcc-mirror/gcc/blob/fbd263526ad105a953fd51d9f7bca2c3f268cf82/libiberty/cp-demangle.c#L3209
---
 src/demangle.cc           | 3 ++-
 src/demangle_unittest.txt | 4 ++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/demangle.cc b/src/demangle.cc
index d7b3af1..dd26914 100644
--- a/src/demangle.cc
+++ b/src/demangle.cc
@@ -1097,10 +1097,11 @@ static bool ParseTemplateArgs(State *state) {
 // <template-arg>  ::= <type>
 //                 ::= <expr-primary>
 //                 ::= I <template-arg>* E        # argument pack
+//                 ::= J <template-arg>* E        # argument pack
 //                 ::= X <expression> E
 static bool ParseTemplateArg(State *state) {
   State copy = *state;
-  if (ParseOneCharToken(state, 'I') &&
+  if ((ParseOneCharToken(state, 'I') || ParseOneCharToken(state, 'J')) &&
       ZeroOrMore(ParseTemplateArg, state) &&
       ParseOneCharToken(state, 'E')) {
     return true;
diff --git a/src/demangle_unittest.txt b/src/demangle_unittest.txt
index 4e23c65..fd6aca0 100644
--- a/src/demangle_unittest.txt
+++ b/src/demangle_unittest.txt
@@ -135,3 +135,7 @@ _ZlsRSoRKSs	operator<<()
 _ZngILi42EEvN1AIXplT_Li2EEE1TE	operator-<>()
 _ZplR1XS0_	operator+()
 _Zrm1XS_	operator%()
+
+# Template argument packs can start with I or J.
+_Z3addIIiEEvDpT_	add<>()
+_Z3addIJiEEvDpT_	add<>()