[libc++] Get rid of _LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS

[ldionne]

Summary

Whether we include operator new and delete into libc++ has always
been a build time setting, and piggy-backing on a macro like
_LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS is inconsistent with how
we handle similar cases for e.g. LIBCXX_ENABLE_RANDOM_DEVICE. Instead,
simply avoid including new.cpp in the sources of the library when we
do not wish to include these operators in the build.

This also makes us much closer to being able to share the definitions
between libc++ and libc++abi, since we could technically build those
definitions into a standalone static library and decide whether we link
it into libc++abi.dylib or libc++.dylib.

[philnik]

libcxx/src/new.cpp

13

Do you plan to move these conditions into CMake? It seems kind-of weird to just ignore LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS in some cases.

[ldionne]

libcxx/src/new.cpp

13

Ideally, I think those should be defined via the CMake cache instead, yeah. Since they also influence what we do for exceptions, I'd like to tackle those independently.

libcxx/CMakeLists.txt

function(cxx_add_basic_build_flags target)
   # library.
   target_compile_definitions(${target} PRIVATE -D_LIBCPP_BUILDING_LIBRARY)
 
   # Make sure the library can be build without transitive includes. This makes
   # it easier to upgrade the library to a newer language standard without build
   # errors.
   target_compile_definitions(${target} PRIVATE -D_LIBCPP_REMOVE_TRANSITIVE_INCLUDES)
 
-  if (NOT LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS)
-    target_compile_definitions(${target} PRIVATE -D_LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS)
-  endif()
-
   if (C_SUPPORTS_COMMENT_LIB_PRAGMA)
     if (LIBCXX_HAS_PTHREAD_LIB)
       target_compile_definitions(${target} PRIVATE -D_LIBCPP_LINK_PTHREAD_LIB)
     endif()
     if (LIBCXX_HAS_RT_LIB)
       target_compile_definitions(${target} PRIVATE -D_LIBCPP_LINK_RT_LIB)
     endif()
   endif()

libcxx/src/CMakeLists.txt

set(LIBCXX_SOURCES
   include/ryu/f2s.h
   include/ryu/ryu.h
   include/to_chars_floating_point.h
   legacy_pointer_safety.cpp
   memory.cpp
   memory_resource.cpp
   mutex.cpp
   mutex_destructor.cpp
-  new.cpp
   new_handler.cpp
   new_helpers.cpp
   optional.cpp
   random_shuffle.cpp
   ryu/d2fixed.cpp
   ryu/d2s.cpp
   ryu/f2s.cpp
   shared_mutex.cpp
if (LIBCXX_ENABLE_FILESYSTEM)
   # definitions. See filesystem/int128_builtins.cpp.
   if (NOT LIBCXX_USE_COMPILER_RT)
     list(APPEND LIBCXX_SOURCES
       filesystem/int128_builtins.cpp
       )
   endif()
 endif()
 
+if (LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS)
+  list(APPEND LIBCXX_SOURCES
+    new.cpp
+    )
+endif()
+
 # Add all the headers to the project for IDEs.
 if (LIBCXX_CONFIGURE_IDE)
   file(GLOB_RECURSE LIBCXX_HEADERS ${CMAKE_CURRENT_SOURCE_DIR}/../include/*)
   if(WIN32)
     file( GLOB LIBCXX_WIN32_HEADERS ${CMAKE_CURRENT_SOURCE_DIR}/../include/__support/win32/*.h)
     list(APPEND LIBCXX_HEADERS ${LIBCXX_WIN32_HEADERS})
   endif()
   # Force them all into the headers dir on MSVC, otherwise they end up at

libcxx/src/new.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include <__memory/aligned_alloc.h>
 #include <cstdlib>
 #include <new>
 
-#if !defined(__GLIBCXX__) &&                                                   \
-    !defined(_LIBCPP_ABI_VCRUNTIME) &&      \
-    !defined(_LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS)
+#if !defined(__GLIBCXX__) && !defined(_LIBCPP_ABI_VCRUNTIME)
 
 // The code below is copied as-is into libc++abi's libcxxabi/src/stdlib_new_delete.cpp
 // file. The version in this file is the canonical one.
 
 // ------------------ BEGIN COPY ------------------
 // 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.

 operator delete[] (void* ptr, size_t, std::align_val_t alignment) noexcept
 {
     ::operator delete[](ptr, alignment);
 }
 
 #endif // !_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
 // ------------------ END COPY ------------------
 
-#endif // !__GLIBCXX__ && !_LIBCPP_ABI_VCRUNTIME && !_LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS
+#endif // !__GLIBCXX__ && !_LIBCPP_ABI_VCRUNTIME