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

[EricWF]

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.

[mehdi_amini]

LGTM

[rmaprath]

Thanks for these patches!

We had some downstream hacks to workaround this, never got around to sort it out. Now it looks much better.

CMakeLists.txt

if (LLVM_HAVE_LINK_VERSION_SCRIPT AND NOT LIBCXX_ENABLE_STATIC_ABI_LIBRARY
       AND LIBCXX_ENABLE_SHARED)
     set(ENABLE_LINKER_SCRIPT_DEFAULT_VALUE ON)
 endif()
 
 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)
 option(LIBCXXABI_ENABLE_STATIC_UNWINDER "Statically link the LLVM unwinder." OFF)
 
 # Target options --------------------------------------------------------------
 option(LIBCXX_BUILD_32_BITS "Build 32 bit libc++." ${LLVM_BUILD_32_BITS})
 set(LIBCXX_SYSROOT "" CACHE STRING "Use alternate sysroot.")

 # visible. This prevents new definitions for inline functions from appearing in
 # the dylib when get ODR used by another function.
 add_compile_flags_if_supported(-fvisibility-inlines-hidden)
 
 # Let the library headers know they are currently being used to build the
 # 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(
     -Wall -Wextra -W -Wwrite-strings
     -Wno-unused-parameter -Wno-long-long
     -Werror=return-type)
 if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
     add_compile_flags_if_supported(

src/new.cpp

#else
     _VSTD::abort();
 #endif
 }
 
 #endif // !LIBSTDCXX
 
 }  // 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
 // that define non-weak copies of the functions.
 
 _LIBCPP_WEAK
 void *
 operator new(std::size_t size) _THROW_BAD_ALLOC

 _LIBCPP_WEAK
 void
 operator delete[] (void* ptr, size_t, std::align_val_t alignment) _NOEXCEPT
 {
     ::operator delete[](ptr, alignment);
 }
 
 #endif // !_LIBCPP_HAS_NO_ALIGNED_ALLOCATION
-#endif // !__GLIBCXX__ && !_LIBCPP_ABI_MICROSOFT
+#endif // !__GLIBCXX__ && !_LIBCPP_ABI_MICROSOFT && !_LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS