[libc++] Add option to disable new/delete overloads when libc++abi provides them.

Summary:
Currently both libc++ and libc++abi provide definitions for operator new/delete. However I believe this is incorrect and that one or the other should offer them.

This patch adds the CMake option `-DLIBCXX_ENABLE_NEW_DELETE_DEFINITIONS` which defaults no `ON` unless `-DLIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS=ON` is specified.



Reviewers: mclow.lists, mehdi_amini, dexonsmith, danalbert, smeenai, mgorny, rmaprath

Reviewed By: mehdi_amini

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D30516

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@296802 91177308-0d34-0410-b5e6-96231b3b80d8

CMakeLists.txt

@@ -157,6 +157,16 @@ option(LIBCXX_ENABLE_ABI_LINKER_SCRIPT
       "Use and install a linker script for the given ABI library"
       ${ENABLE_LINKER_SCRIPT_DEFAULT_VALUE})
 
+set(ENABLE_NEW_DELETE_DEFAULT ON)
+if (LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS)
+  set(ENABLE_NEW_DELETE_DEFAULT OFF)
+endif()
+
+option(LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS
+    "Build libc++ with definitions for operator new/delete. This option can
+    be used to disable the definitions when libc++abi is expected to provide
+    them" ${ENABLE_NEW_DELETE_DEFAULT})
+
 # Build libc++abi with libunwind. We need this option to determine whether to
 # link with libunwind or libgcc_s while running the test cases.
 option(LIBCXXABI_USE_LLVM_UNWINDER "Build and use the LLVM unwinder." OFF)
@@ -433,6 +443,10 @@ add_compile_flags_if_supported(-fvisibility-inlines-hidden)
 # library.
 add_definitions(-D_LIBCPP_BUILDING_LIBRARY)
 
+if (NOT LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS)
+  add_definitions(-D_LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS)
+endif()
+
 # Warning flags ===============================================================
 add_definitions(-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 add_compile_flags_if_supported(

src/new.cpp

@@ -53,7 +53,8 @@ __throw_bad_alloc()
 
 }  // std
 
-#if !defined(__GLIBCXX__) && !defined(_LIBCPP_ABI_MICROSOFT)
+#if !defined(__GLIBCXX__) && !defined(_LIBCPP_ABI_MICROSOFT) && \
+    !defined(_LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS)
 
 // Implement all new and delete operators as weak definitions
 // in this shared library, so that they can be overridden by programs
@@ -298,4 +299,4 @@ operator delete[] (void* ptr, size_t, std::align_val_t alignment) _NOEXCEPT
 }
 
 #endif // !_LIBCPP_HAS_NO_ALIGNED_ALLOCATION
-#endif // !__GLIBCXX__ && !_LIBCPP_ABI_MICROSOFT
+#endif // !__GLIBCXX__ && !_LIBCPP_ABI_MICROSOFT && !_LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS