From c7cd73e8b89ae0a37ed056a9dbad9e6af42a255c Mon Sep 17 00:00:00 2001
From: Shoaib Meenai <smeenai@fb.com>
Date: Tue, 28 Mar 2017 19:33:31 +0000
Subject: [PATCH] [libc++] Add a key function for bad_function_call

Summary:
bad_function_call is currently an empty class, so any object files using
that class will end up with their own copy of its typeinfo, typeinfo
name and vtable, leading to unnecessary duplication that has to be
resolved by the dynamic linker. Instead, give bad_function_call a key
function and put a definition for that key function in libc++ itself, to
centralize the typeinfo and vtable.

This is consistent with the behavior for other exception classes. The
key functions are defined in libc++ rather than libc++abi since the
class is defined in the libc++ versioning namespace, so ABI
compatibility with libstdc++ is not a concern.

Guard this change behind an ABI macro, since it isn't backwards
compatible (i.e., clients built against the new libc++ headers wouldn't
be able to run against an older libc++ library).

Reviewers: mclow.lists, EricWF

Subscribers: mgorny, cfe-commits

Differential Revision: https://reviews.llvm.org/D27387

llvm-svn: 298937
---
 libcxx/include/__config   |  4 ++++
 libcxx/include/functional |  6 ++++++
 libcxx/lib/CMakeLists.txt |  2 +-
 libcxx/src/functional.cpp | 26 ++++++++++++++++++++++++++
 4 files changed, 37 insertions(+), 1 deletion(-)
 create mode 100644 libcxx/src/functional.cpp

diff --git a/libcxx/include/__config b/libcxx/include/__config
index 9b48a70..c847418 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -58,6 +58,10 @@
 // `pointer_safety` and `get_pointer_safety()` will no longer be available
 // in C++03.
 #define _LIBCPP_ABI_POINTER_SAFETY_ENUM_TYPE
+// Define a key function for `bad_function_call` in the library, to centralize
+// its vtable and typeinfo to libc++ rather than having all other libraries
+// using that class define their own copies.
+#define _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
 #elif _LIBCPP_ABI_VERSION == 1
 #if !defined(_WIN32)
 // Enable compiling copies of now inline methods into the dylib to support
diff --git a/libcxx/include/functional b/libcxx/include/functional
index 977ada6..fecac4e 100644
--- a/libcxx/include/functional
+++ b/libcxx/include/functional
@@ -1389,6 +1389,12 @@ mem_fn(_Rp _Tp::* __pm) _NOEXCEPT
 class _LIBCPP_EXCEPTION_ABI bad_function_call
     : public exception
 {
+#ifdef _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
+public:
+    virtual ~bad_function_call() _NOEXCEPT;
+
+    virtual const char* what() const _NOEXCEPT;
+#endif
 };
 
 _LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
diff --git a/libcxx/lib/CMakeLists.txt b/libcxx/lib/CMakeLists.txt
index 66bb14c..a8dd4eb 100644
--- a/libcxx/lib/CMakeLists.txt
+++ b/libcxx/lib/CMakeLists.txt
@@ -177,7 +177,7 @@ endif()
 split_list(LIBCXX_COMPILE_FLAGS)
 split_list(LIBCXX_LINK_FLAGS)
 
-# Add a object library that contains the compiled source files.
+# Add an object library that contains the compiled source files.
 add_library(cxx_objects OBJECT ${exclude_from_all} ${LIBCXX_SOURCES} ${LIBCXX_HEADERS})
 if(WIN32 AND NOT MINGW)
   target_compile_definitions(cxx_objects
diff --git a/libcxx/src/functional.cpp b/libcxx/src/functional.cpp
new file mode 100644
index 0000000..5c2646f
--- /dev/null
+++ b/libcxx/src/functional.cpp
@@ -0,0 +1,26 @@
+//===----------------------- functional.cpp -------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "functional"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#ifdef _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
+bad_function_call::~bad_function_call() _NOEXCEPT
+{
+}
+
+const char*
+bad_function_call::what() const _NOEXCEPT
+{
+    return "std::bad_function_call";
+}
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
-- 
2.7.4