[runtimes] Never define operator new in libc++ by ldionne · Pull Request #218989 · llvm/llvm-project

ldionne · 2026-08-26T17:14:30Z

Libc++ and libc++abi have allowed picking whether operator new is defined inside libc++ or libc++abi for a long time. By default, the operators are defined inside libc++abi, and most platforms use that.

The possibility of defining operator new in either library causes significant complexity since we have to maintain an includable source that must work from both libc++ and libc++abi. While working on #215813 where we must detect whether operator new has been overridden from a function we'd want to define in libc++.dylib, it became apparent how brittle that setup is.

This patch removes the option to define operator new in libc++. The operators are either defined in libc++abi or not at all.

While this may seem like a major breakage, in reality I believe this does not affect most platforms. Indeed, platforms that use the default configuration are not affected. Of the platforms that explicitly put the operators in libc++.dylib, it seems that most of them are also merging libc++abi into libc++, so it does not actually matter where the operators are coming from.

The one platform where a change would be required is FreeBSD, which uses libcxxrt and seems to really depend on the operators being defined in libc++.dylib.

Libc++ and libc++abi have allowed picking whether `operator new` is defined inside libc++ or libc++abi for a long time. By default, the operators are defined inside libc++abi, and most platforms use that. The possibility of defining `operator new` in either library causes significant complexity since we have to maintain an includable source that must work from both libc++ and libc++abi. While working on llvm#215813 where we must detect whether `operator new` has been overridden from a function we'd want to define in `libc++.dylib`, it became apparent how brittle that setup is. This patch removes the option to define `operator new` in libc++. The operators are either defined in libc++abi or not at all. While this may seem like a major breakage, in reality I believe this does not affect most platforms. Indeed, platforms that use the default configuration are not affected. Of the platforms that explicitly put the operators in `libc++.dylib`, it seems that most of them are also merging libc++abi into libc++, so it does not actually matter where the operators are coming from. The one platform where a change would be required is FreeBSD, which uses libcxxrt and seems to really depend on the operators being defined in libc++.dylib.

llvmorg-github-actions · 2026-08-26T17:19:41Z

@llvm/pr-subscribers-backend-amdgpu
@llvm/pr-subscribers-libcxxabi

@llvm/pr-subscribers-libcxx

Author: Louis Dionne (ldionne)

Changes

Libc++ and libc++abi have allowed picking whether operator new is defined inside libc++ or libc++abi for a long time. By default, the operators are defined inside libc++abi, and most platforms use that.

The possibility of defining operator new in either library causes significant complexity since we have to maintain an includable source that must work from both libc++ and libc++abi. While working on #215813 where we must detect whether operator new has been overridden from a function we'd want to define in libc++.dylib, it became apparent how brittle that setup is.

This patch removes the option to define operator new in libc++. The operators are either defined in libc++abi or not at all.

While this may seem like a major breakage, in reality I believe this does not affect most platforms. Indeed, platforms that use the default configuration are not affected. Of the platforms that explicitly put the operators in libc++.dylib, it seems that most of them are also merging libc++abi into libc++, so it does not actually matter where the operators are coming from.

The one platform where a change would be required is FreeBSD, which uses libcxxrt and seems to really depend on the operators being defined in libc++.dylib.

Patch is 20.08 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/218989.diff

24 Files Affected:

(modified) clang/cmake/caches/Apple-stage1.cmake (-3)
(modified) clang/cmake/caches/CrossWinToARMLinux.cmake (+2-4)
(modified) clang/cmake/caches/Fuchsia-stage2.cmake (-4)
(modified) clang/cmake/caches/cross-linux-toolchain.cmake (-1)
(modified) libcxx/CMakeLists.txt (+6-5)
(modified) libcxx/cmake/caches/AMDGPU.cmake (-2)
(modified) libcxx/cmake/caches/FreeBSD.cmake (-1)
(modified) libcxx/cmake/caches/NVPTX.cmake (-2)
(modified) libcxx/docs/ReleaseNotes/24.rst (+3)
(modified) libcxx/docs/VendorDocumentation.rst (+3-2)
(modified) libcxx/lib/abi/CMakeLists.txt (+1-7)
(renamed) libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.abilist ()
(renamed) libcxx/lib/abi/i686-linux-android23.libcxxabi.v1.stable.exceptions.abilist ()
(renamed) libcxx/lib/abi/powerpc-ibm-aix.libcxxabi.v1.stable.exceptions.abilist ()
(renamed) libcxx/lib/abi/powerpc64-ibm-aix.libcxxabi.v1.stable.exceptions.abilist ()
(renamed) libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.abilist ()
(renamed) libcxx/lib/abi/x86_64-linux-android23.libcxxabi.v1.stable.exceptions.abilist ()
(renamed) libcxx/lib/abi/x86_64-unknown-freebsd.libcxxabi.v1.stable.exceptions.abilist ()
(renamed) libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.abilist ()
(renamed) libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.noexceptions.abilist ()
(modified) libcxx/src/CMakeLists.txt (-22)
(removed) libcxx/src/new.cpp (-20)
(modified) libcxx/src/support/new.ipp (+2)
(modified) libcxxabi/CMakeLists.txt (+2-3)

diff --git a/clang/cmake/caches/Apple-stage1.cmake b/clang/cmake/caches/Apple-stage1.cmake
index 36937f6ed0b4b..ed30fcfc9cd3d 100644
--- a/clang/cmake/caches/Apple-stage1.cmake
+++ b/clang/cmake/caches/Apple-stage1.cmake
@@ -34,9 +34,6 @@ set(COMPILER_RT_ENABLE_TVOS OFF CACHE BOOL "")
 set(BOOTSTRAP_LLVM_ENABLE_LTO ON CACHE BOOL "")
 set(CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
 
-set(LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS OFF CACHE BOOL "")
-set(LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS ON CACHE BOOL "")
-
 set(CLANG_BOOTSTRAP_TARGETS
   generate-order-file
   check-all
diff --git a/clang/cmake/caches/CrossWinToARMLinux.cmake b/clang/cmake/caches/CrossWinToARMLinux.cmake
index c47c4ac3bb73e..1a63ededd867d 100644
--- a/clang/cmake/caches/CrossWinToARMLinux.cmake
+++ b/clang/cmake/caches/CrossWinToARMLinux.cmake
@@ -21,7 +21,7 @@
 #  cmake -G Ninja ^
 #       -DTOOLCHAIN_TARGET_TRIPLE=aarch64-unknown-linux-gnu ^
 #       -DTOOLCHAIN_TARGET_SYSROOTFS=<path-to-develop-arm-linux-root-fs> ^
-#       -DTOOLCHAIN_SHARED_LIBS=OFF ^ 
+#       -DTOOLCHAIN_SHARED_LIBS=OFF ^
 #       -DCMAKE_INSTALL_PREFIX=../install ^
 #       -DCMAKE_CXX_FLAGS="-D__OPTIMIZE__" ^
 #       -DREMOTE_TEST_HOST="<hostname>" ^
@@ -205,21 +205,19 @@ set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_COMPILER_RT_CXX_LIBRARY
 # The compiler-rt tests disable the clang configuration files during the execution by setting CLANG_NO_DEFAULT_CONFIG=1
 # and drops out the --sysroot from there. Provide it explicity via the test flags here if target sysroot has been specified.
 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_COMPILER_RT_TEST_COMPILER_CFLAGS          "--stdlib=libc++ ${sysroot_flags}" CACHE STRING "")
-  
+
 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBUNWIND_USE_COMPILER_RT                 ON CACHE BOOL "")
 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBUNWIND_ENABLE_SHARED                   ${TOOLCHAIN_SHARED_LIBS} CACHE BOOL "")
 
 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXXABI_USE_LLVM_UNWINDER               ON CACHE BOOL "")
 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXXABI_ENABLE_STATIC_UNWINDER          ${TOOLCHAIN_USE_STATIC_LIBS} CACHE BOOL "")
 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXXABI_USE_COMPILER_RT                 ON CACHE BOOL "")
-set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS   OFF CACHE BOOL "")
 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXXABI_ENABLE_SHARED                   ${TOOLCHAIN_SHARED_LIBS} CACHE BOOL "")
 
 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXX_USE_COMPILER_RT                    ON CACHE BOOL "")
 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXX_ENABLE_SHARED                      ${TOOLCHAIN_SHARED_LIBS} CACHE BOOL "")
 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXX_ABI_VERSION                        ${LIBCXX_ABI_VERSION} CACHE STRING "")
 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXX_CXX_ABI                            "libcxxabi" CACHE STRING "")    #!!!
-set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS      ON CACHE BOOL "")
 # Merge libc++ and libc++abi libraries into the single libc++ library file.
 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXX_ENABLE_STATIC_ABI_LIBRARY          ${TOOLCHAIN_USE_STATIC_LIBS} CACHE BOOL "")
 # Forcely disable the libc++ benchmarks on Windows build hosts
diff --git a/clang/cmake/caches/Fuchsia-stage2.cmake b/clang/cmake/caches/Fuchsia-stage2.cmake
index 9d549fe94f43c..f22c657040701 100644
--- a/clang/cmake/caches/Fuchsia-stage2.cmake
+++ b/clang/cmake/caches/Fuchsia-stage2.cmake
@@ -282,7 +282,6 @@ if(FUCHSIA_SDK)
     set(RUNTIMES_${target}+asan_LLVM_BUILD_COMPILER_RT OFF CACHE BOOL "")
     set(RUNTIMES_${target}+asan_LLVM_USE_SANITIZER "Address" CACHE STRING "")
     set(RUNTIMES_${target}+asan_LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS OFF CACHE BOOL "")
-    set(RUNTIMES_${target}+asan_LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS OFF CACHE BOOL "")
 
     set(RUNTIMES_${target}+noexcept_LLVM_BUILD_COMPILER_RT OFF CACHE BOOL "")
     set(RUNTIMES_${target}+noexcept_LIBCXXABI_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
@@ -291,7 +290,6 @@ if(FUCHSIA_SDK)
     set(RUNTIMES_${target}+asan+noexcept_LLVM_BUILD_COMPILER_RT OFF CACHE BOOL "")
     set(RUNTIMES_${target}+asan+noexcept_LLVM_USE_SANITIZER "Address" CACHE STRING "")
     set(RUNTIMES_${target}+asan+noexcept_LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS OFF CACHE BOOL "")
-    set(RUNTIMES_${target}+asan+noexcept_LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS OFF CACHE BOOL "")
     set(RUNTIMES_${target}+asan+noexcept_LIBCXXABI_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
     set(RUNTIMES_${target}+asan+noexcept_LIBCXX_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
 
@@ -307,13 +305,11 @@ if(FUCHSIA_SDK)
   set(RUNTIMES_aarch64-unknown-fuchsia+hwasan_LLVM_BUILD_COMPILER_RT OFF CACHE BOOL "")
   set(RUNTIMES_aarch64-unknown-fuchsia+hwasan_LLVM_USE_SANITIZER "HWAddress" CACHE STRING "")
   set(RUNTIMES_aarch64-unknown-fuchsia+hwasan_LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS OFF CACHE BOOL "")
-  set(RUNTIMES_aarch64-unknown-fuchsia+hwasan_LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS OFF CACHE BOOL "")
 
   # HWASan+noexcept
   set(RUNTIMES_aarch64-unknown-fuchsia+hwasan+noexcept_LLVM_BUILD_COMPILER_RT OFF CACHE BOOL "")
   set(RUNTIMES_aarch64-unknown-fuchsia+hwasan+noexcept_LLVM_USE_SANITIZER "HWAddress" CACHE STRING "")
   set(RUNTIMES_aarch64-unknown-fuchsia+hwasan+noexcept_LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS OFF CACHE BOOL "")
-  set(RUNTIMES_aarch64-unknown-fuchsia+hwasan+noexcept_LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS OFF CACHE BOOL "")
   set(RUNTIMES_aarch64-unknown-fuchsia+hwasan+noexcept_LIBCXXABI_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
   set(RUNTIMES_aarch64-unknown-fuchsia+hwasan+noexcept_LIBCXX_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
 
diff --git a/clang/cmake/caches/cross-linux-toolchain.cmake b/clang/cmake/caches/cross-linux-toolchain.cmake
index 8065961f7fcfe..fc456831a7892 100644
--- a/clang/cmake/caches/cross-linux-toolchain.cmake
+++ b/clang/cmake/caches/cross-linux-toolchain.cmake
@@ -273,7 +273,6 @@ foreach(target ${LLVM_RUNTIME_TARGETS})
 
   set(RUNTIMES_${target}_LIBCXX_USE_COMPILER_RT                    ON CACHE BOOL "")
   set(RUNTIMES_${target}_LIBCXX_CXX_ABI                            "libcxxabi" CACHE STRING "")    #!!!
-  set(RUNTIMES_${target}_LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS      ON CACHE BOOL "")
 
 
   if (DEFINED TOOLCHAIN_SHARED_LIBS)
diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
index e28bbfaa0605d..fcd7b1e6095f3 100644
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -296,11 +296,12 @@ option(LIBCXX_ENABLE_ABI_LINKER_SCRIPT
       "Use and install a linker script for the given ABI library"
       ${ENABLE_LINKER_SCRIPT_DEFAULT_VALUE})
 
-option(LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS
-  "Build libc++ with definitions for operator new/delete. These are normally
-   defined in libc++abi, but this option can be used to define them in libc++
-   instead. If you define them in libc++, make sure they are NOT defined in
-   libc++abi. Doing otherwise is an ODR violation." OFF)
+# TODO: Remove in LLVM 25
+if (LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS)
+  message(FATAL_ERROR "LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS is not supported anymore, operator new is now either
+                       provided by an ABI library like libc++abi.dylib, or not at all")
+endif()
+
 # 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." ON)
diff --git a/libcxx/cmake/caches/AMDGPU.cmake b/libcxx/cmake/caches/AMDGPU.cmake
index ed6e5d78149e7..bf4ba024f7d93 100644
--- a/libcxx/cmake/caches/AMDGPU.cmake
+++ b/libcxx/cmake/caches/AMDGPU.cmake
@@ -4,7 +4,6 @@ set(LIBCXX_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
 set(LIBCXX_ENABLE_FILESYSTEM OFF CACHE BOOL "")
 set(LIBCXX_ENABLE_LOCALIZATION ON CACHE BOOL "")
 set(LIBCXX_ENABLE_MONOTONIC_CLOCK ON CACHE BOOL "")
-set(LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS ON CACHE BOOL "")
 set(LIBCXX_ENABLE_RANDOM_DEVICE OFF CACHE BOOL "")
 set(LIBCXX_ENABLE_RTTI OFF CACHE BOOL "")
 set(LIBCXX_ENABLE_SHARED OFF CACHE BOOL "")
@@ -22,7 +21,6 @@ set(RUNTIMES_USE_LIBC "llvm-libc" CACHE STRING "")
 # Configuration options for libcxxabi.
 set(LIBCXXABI_BAREMETAL ON CACHE BOOL "")
 set(LIBCXXABI_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
-set(LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS OFF CACHE BOOL "")
 set(LIBCXXABI_ENABLE_SHARED OFF CACHE BOOL "")
 set(LIBCXXABI_ENABLE_THREADS OFF CACHE BOOL "")
 set(LIBCXXABI_USE_LLVM_UNWINDER OFF CACHE BOOL "")
diff --git a/libcxx/cmake/caches/FreeBSD.cmake b/libcxx/cmake/caches/FreeBSD.cmake
index 7a7d917922b53..7ca4ae863f001 100644
--- a/libcxx/cmake/caches/FreeBSD.cmake
+++ b/libcxx/cmake/caches/FreeBSD.cmake
@@ -5,4 +5,3 @@ set(LIBCXX_ABI_VERSION "1" CACHE STRING "")
 set(LIBCXX_ENABLE_STATIC ON CACHE BOOL "")
 set(LIBCXX_ENABLE_SHARED ON CACHE BOOL "")
 set(LIBCXX_CXX_ABI libcxxrt CACHE STRING "")
-set(LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS ON CACHE BOOL "")
diff --git a/libcxx/cmake/caches/NVPTX.cmake b/libcxx/cmake/caches/NVPTX.cmake
index 34e9cb9a1ddd1..d2733141a4297 100644
--- a/libcxx/cmake/caches/NVPTX.cmake
+++ b/libcxx/cmake/caches/NVPTX.cmake
@@ -4,7 +4,6 @@ set(LIBCXX_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
 set(LIBCXX_ENABLE_FILESYSTEM OFF CACHE BOOL "")
 set(LIBCXX_ENABLE_LOCALIZATION ON CACHE BOOL "")
 set(LIBCXX_ENABLE_MONOTONIC_CLOCK ON CACHE BOOL "")
-set(LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS ON CACHE BOOL "")
 set(LIBCXX_ENABLE_RANDOM_DEVICE OFF CACHE BOOL "")
 set(LIBCXX_ENABLE_RTTI OFF CACHE BOOL "")
 set(LIBCXX_ENABLE_SHARED OFF CACHE BOOL "")
@@ -22,7 +21,6 @@ set(RUNTIMES_USE_LIBC "llvm-libc" CACHE STRING "")
 # Configuration options for libcxxabi.
 set(LIBCXXABI_BAREMETAL ON CACHE BOOL "")
 set(LIBCXXABI_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
-set(LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS OFF CACHE BOOL "")
 set(LIBCXXABI_ENABLE_SHARED OFF CACHE BOOL "")
 set(LIBCXXABI_ENABLE_THREADS OFF CACHE BOOL "")
 set(LIBCXXABI_USE_LLVM_UNWINDER OFF CACHE BOOL "")
diff --git a/libcxx/docs/ReleaseNotes/24.rst b/libcxx/docs/ReleaseNotes/24.rst
index 9cf08b5732970..948b364741ee5 100644
--- a/libcxx/docs/ReleaseNotes/24.rst
+++ b/libcxx/docs/ReleaseNotes/24.rst
@@ -91,3 +91,6 @@ ABI Affecting Changes
 
 Build System Changes
 --------------------
+
+- The ``LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS`` option has been removed. The various ``operator new`` functions are
+  now either defined in libc++abi or not at all (which still allows for them being provided by an external library).
diff --git a/libcxx/docs/VendorDocumentation.rst b/libcxx/docs/VendorDocumentation.rst
index 38fd5ac73e222..d217250229be2 100644
--- a/libcxx/docs/VendorDocumentation.rst
+++ b/libcxx/docs/VendorDocumentation.rst
@@ -581,7 +581,9 @@ Using libcxxrt on Linux
 
 You will need to keep the source tree of `libcxxrt`_ available
 on your build machine and your copy of the libcxxrt shared library must
-be placed where your linker will find it.
+be placed where your linker will find it. You must use a recent version
+of libcxxrt since historical versions did not provide the necessary
+definitions of ``operator new``.
 
 We can now run CMake like:
 
@@ -590,7 +592,6 @@ We can now run CMake like:
   $ cmake -G Ninja -S runtimes -B build                               \
           -DLLVM_ENABLE_RUNTIMES="libcxx"                             \
           -DLIBCXX_CXX_ABI=libcxxrt                                   \
-          -DLIBCXX_ENABLE_NEW_DELETE_DEFINITIONS=ON                   \
           -DLIBCXXABI_USE_LLVM_UNWINDER=OFF                           \
           -DLIBCXX_CXX_ABI_INCLUDE_PATHS=path/to/libcxxrt-sources/src
   $ ninja -C build install-cxx
diff --git a/libcxx/lib/abi/CMakeLists.txt b/libcxx/lib/abi/CMakeLists.txt
index 8f277aad2dcd5..d3151e1939973 100644
--- a/libcxx/lib/abi/CMakeLists.txt
+++ b/libcxx/lib/abi/CMakeLists.txt
@@ -7,7 +7,7 @@
 # Right now, this is done by using the ABI identifier as the filename containing
 # the list of symbols exported by libc++ for that configuration, however we could
 # make it more sophisticated if the number of ABI-affecting parameters grew.
-function(cxx_abi_list_identifier result triple abi_library abi_version unstable exceptions new_delete_in_libcxx)
+function(cxx_abi_list_identifier result triple abi_library abi_version unstable exceptions)
   set(abi_properties)
 
   if ("${triple}" MATCHES "darwin")
@@ -33,11 +33,6 @@ function(cxx_abi_list_identifier result triple abi_library abi_version unstable
   else()
     list(APPEND abi_properties "noexceptions")
   endif()
-  if (${new_delete_in_libcxx})
-    list(APPEND abi_properties "new")
-  else()
-    list(APPEND abi_properties "nonew")
-  endif()
 
   list(JOIN abi_properties "." tmp)
   set(${result} "${tmp}" PARENT_SCOPE)
@@ -54,7 +49,6 @@ cxx_abi_list_identifier(abi_list_identifier
   "${LIBCXX_ABI_VERSION}"
   "${LIBCXX_ABI_UNSTABLE}"
   "${LIBCXX_ENABLE_EXCEPTIONS}"
-  "${LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS}"
 )
 
 if (TARGET cxx_shared)
diff --git a/libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.abilist
similarity index 100%
rename from libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist
rename to libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.abilist
diff --git a/libcxx/lib/abi/i686-linux-android23.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/i686-linux-android23.libcxxabi.v1.stable.exceptions.abilist
similarity index 100%
rename from libcxx/lib/abi/i686-linux-android23.libcxxabi.v1.stable.exceptions.nonew.abilist
rename to libcxx/lib/abi/i686-linux-android23.libcxxabi.v1.stable.exceptions.abilist
diff --git a/libcxx/lib/abi/powerpc-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/powerpc-ibm-aix.libcxxabi.v1.stable.exceptions.abilist
similarity index 100%
rename from libcxx/lib/abi/powerpc-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist
rename to libcxx/lib/abi/powerpc-ibm-aix.libcxxabi.v1.stable.exceptions.abilist
diff --git a/libcxx/lib/abi/powerpc64-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/powerpc64-ibm-aix.libcxxabi.v1.stable.exceptions.abilist
similarity index 100%
rename from libcxx/lib/abi/powerpc64-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist
rename to libcxx/lib/abi/powerpc64-ibm-aix.libcxxabi.v1.stable.exceptions.abilist
diff --git a/libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.abilist
similarity index 100%
rename from libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist
rename to libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.abilist
diff --git a/libcxx/lib/abi/x86_64-linux-android23.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/x86_64-linux-android23.libcxxabi.v1.stable.exceptions.abilist
similarity index 100%
rename from libcxx/lib/abi/x86_64-linux-android23.libcxxabi.v1.stable.exceptions.nonew.abilist
rename to libcxx/lib/abi/x86_64-linux-android23.libcxxabi.v1.stable.exceptions.abilist
diff --git a/libcxx/lib/abi/x86_64-unknown-freebsd.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/x86_64-unknown-freebsd.libcxxabi.v1.stable.exceptions.abilist
similarity index 100%
rename from libcxx/lib/abi/x86_64-unknown-freebsd.libcxxabi.v1.stable.exceptions.nonew.abilist
rename to libcxx/lib/abi/x86_64-unknown-freebsd.libcxxabi.v1.stable.exceptions.abilist
diff --git a/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.abilist
similarity index 100%
rename from libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.nonew.abilist
rename to libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.abilist
diff --git a/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.noexceptions.nonew.abilist b/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.noexceptions.abilist
similarity index 100%
rename from libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.noexceptions.nonew.abilist
rename to libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.noexceptions.abilist
diff --git a/libcxx/src/CMakeLists.txt b/libcxx/src/CMakeLists.txt
index e029f9f29d5ea..d2354b74db7ce 100644
--- a/libcxx/src/CMakeLists.txt
+++ b/libcxx/src/CMakeLists.txt
@@ -135,12 +135,6 @@ if (LIBCXX_ENABLE_FILESYSTEM)
   endif()
 endif()
 
-if (LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS)
-  list(APPEND LIBCXX_SOURCES
-    new.cpp
-    )
-endif()
-
 if (APPLE AND LLVM_USE_SANITIZER)
   if (("${LLVM_USE_SANITIZER}" STREQUAL "Address") OR
       ("${LLVM_USE_SANITIZER}" STREQUAL "Address;Undefined") OR
@@ -277,22 +271,6 @@ set_target_properties(cxx_static
 )
 cxx_add_common_build_flags(cxx_static)
 
-if (LIBCXX_HERMETIC_STATIC_LIBRARY)
-  # If the hermetic library doesn't define the operator new/delete functions
-  # then its code shouldn't declare them with hidden visibility.  They might
-  # actually be provided by a shared library at link time.
-  if (LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS)
-    append_flags_if_supported(CXX_STATIC_LIBRARY_FLAGS -fvisibility-global-new-delete=force-hidden)
-    if (NOT CXX_SUPPORTS_FVISIBILITY_GLOBAL_NEW_DELETE_EQ_FORCE_HIDDEN_FLAG)
-      append_flags_if_supported(CXX_STATIC_LIBRARY_FLAGS -fvisibility-global-new-delete-hidden)
-    endif()
-  endif()
-  target_compile_options(cxx_static PRIVATE ${CXX_STATIC_LIBRARY_FLAGS})
-  # _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS can be defined in __config_site
-  # too. Define it in the same way here, to avoid redefinition conflicts.
-  target_compile_definitions(cxx_static PRIVATE _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS=)
-endif()
-
 # Attempt to merge the libc++.a archive and the ABI library archive into one.
 if (LIBCXX_STATICALLY_LINK_ABI_IN_STATIC_LIBRARY)
   target_link_libraries(cxx_static PRIVATE libcxx-abi-static-objects)
diff --git a/libcxx/src/new.cpp b/libcxx/src/new.cpp
deleted file mode 100644
index 618b4348f1f94..0000000000000
--- a/libcxx/src/new.cpp
+++ /dev/null
@@ -1,20 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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 <__assert>
-#include <new>
-
-#if !defined(__GLIBCXX__) && !defined(_LIBCPP_ABI_VCRUNTIME)
-
-inline void __throw_bad_alloc_shim() { std::__throw_bad_alloc(); }
-
-#  define _LIBCPP_ASSERT_SHIM(expr, str) _LIBCPP_ASSERT(expr, str)
-
-#  include "support/new.ipp"
-
-#endif // !__GLIBCXX__ && !_LIBCPP_ABI_VCRUNTIME
diff --git a/libcxx/src/support/new.ipp b/libcxx/src/support/new.ipp
index 2f3af29f99378..a745388be958b 100644
--- a/libcxx/src/support/new.ipp
+++ b/libcxx/src/support/new.ipp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// TODO: This file is now only used from libc++abi. Simplify the implementation accordingly.
+
 #include <cstddef>
 #include <cstdlib>
 #include <new>
diff --git a/libcxxabi/CMakeLists.txt b/libcxxabi/CMakeLists.txt
index 902d4247fe6f7..bc008cef2f887 100644
--- a/libcxxabi/CMakeLists.txt
+++ b/libcxxabi/CMakeLists.txt
@@ -83,9 +83,8 @@ library to try comparing the type_info names to see if they are equal \
 instead." OFF)
 
 option(LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS
-  "Build libc++abi with definitions for operator new/delete. These are normally
-   defined in libc++abi, but it is also possible to define them in libc++, in
-   which case the definition in libc++abi should be turned off." ON)
+  "Build libc++abi with definitions for operator new/delete. It is possible to turn this off if
+   these definitions are provided by another library (e.g. sanitizers)." ON)
 option(LIBCXXABI_BUILD_32_BITS "Build 32 bit multilib libc++abi. This option is not supported anymore when building the runtimes. Please specify a full triple instead." ${LLVM_BUILD_32_BITS})
 if (LIBCXXABI_BUILD_32_BITS)
   message(FATAL_ERROR "LIBCXXABI_BUILD_32_BITS is not suppo...
[truncated]

ldionne

Pinging the relevant people for each platform.

ldionne · 2026-08-26T17:17:29Z

 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXX_ENABLE_SHARED                      ${TOOLCHAIN_SHARED_LIBS} CACHE BOOL "")
 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXX_ABI_VERSION                        ${LIBCXX_ABI_VERSION} CACHE STRING "")
 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXX_CXX_ABI                            "libcxxabi" CACHE STRING "")    #!!!
-set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS      ON CACHE BOOL "")


@vvereschaka I am assuming that this change would not impact your configuration, since you seem to be merging libc++abi into libc++.

Do you have a mechanism to re-export operator new symbols from libc++abi to libc++ when you don't merge the two libraries? If not, then perhaps a program that links against -lc++ but not explicitly -lc++abi today would fail to link after this change, but I don't think that's something that should ever happen?

ldionne · 2026-08-26T17:18:03Z

    set(RUNTIMES_${target}+asan_LLVM_BUILD_COMPILER_RT OFF CACHE BOOL "")
    set(RUNTIMES_${target}+asan_LLVM_USE_SANITIZER "Address" CACHE STRING "")
    set(RUNTIMES_${target}+asan_LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS OFF CACHE BOOL "")
-    set(RUNTIMES_${target}+asan_LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS OFF CACHE BOOL "")


@petrhosek This should be a no-op for you since you were already turning this off so they can be overridden by the sanitizer versions.

ldionne · 2026-08-26T17:19:37Z

 set(LIBCXX_ENABLE_FILESYSTEM OFF CACHE BOOL "")
 set(LIBCXX_ENABLE_LOCALIZATION ON CACHE BOOL "")
 set(LIBCXX_ENABLE_MONOTONIC_CLOCK ON CACHE BOOL "")
-set(LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS ON CACHE BOOL "")


@jhuber6 Since you're already merging libc++abi into libc++, I don't think it matters where those operators are defined.

ldionne · 2026-08-26T17:21:11Z

 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXXABI_USE_LLVM_UNWINDER               ON CACHE BOOL "")
 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXXABI_ENABLE_STATIC_UNWINDER          ${TOOLCHAIN_USE_STATIC_LIBS} CACHE BOOL "")
 set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXXABI_USE_COMPILER_RT                 ON CACHE BOOL "")
-set(RUNTIMES_${TOOLCHAIN_TARGET_TRIPLE}_LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS   OFF CACHE BOOL "")


Since the default is ON, this removal basically makes the definitions live in libc++abi instead of libc++ for this configuration.

ldionne · 2026-08-26T17:23:00Z


  set(RUNTIMES_${target}_LIBCXXABI_USE_LLVM_UNWINDER               ON CACHE BOOL "")
  set(RUNTIMES_${target}_LIBCXXABI_USE_COMPILER_RT                 ON CACHE BOOL "")
-  set(RUNTIMES_${target}_LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS   OFF CACHE BOOL "")


@vvereschaka Similarly here, this should only move operator new from libc++ to libc++abi, which should work assuming you link against both (and I assume you do).

ldionne · 2026-08-26T17:24:28Z

 set(BOOTSTRAP_LLVM_ENABLE_LTO ON CACHE BOOL "")
 set(CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")

-set(LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS OFF CACHE BOOL "")


This is just re-stating the defaults, so this is a no-op.

ldionne · 2026-08-26T17:27:15Z

 set(LIBCXX_ENABLE_STATIC ON CACHE BOOL "")
 set(LIBCXX_ENABLE_SHARED ON CACHE BOOL "")
 set(LIBCXX_CXX_ABI libcxxrt CACHE STRING "")
-set(LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS ON CACHE BOOL "")


@emaste @jrtc27 This change is the only one in this patch that I expect to cause problems. FreeBSD currently defines operator new in libc++.so because (AFAICT) it uses libcxxrt, which does not define all the necessary variants of operator new. I believe the best path forward here would be to ask libcxxrt to implement those missing variants of operator new, and to simply not use operator new from either libc++ or libc++abi. This would align FreeBSD with what other platforms are doing.

It's a bit of a pain, but probably a maintenance task that is overdue. cc @davidchisnall for possible libcxxrt input. :)

We can add the missing ones to libcxxrt quite easily. We didn't because it's mostly used with libc++, which defined them and we regarded them as a small set to be used with things that didn't link a standard library.

ldionne · 2026-08-26T17:30:55Z

 set(LIBCXX_ENABLE_FILESYSTEM OFF CACHE BOOL "")
 set(LIBCXX_ENABLE_LOCALIZATION ON CACHE BOOL "")
 set(LIBCXX_ENABLE_MONOTONIC_CLOCK ON CACHE BOOL "")
-set(LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS ON CACHE BOOL "")


@jhuber6 Same here: since libc++abi and libc++ are merged, I don't think it matters where the operators are defined. So I expect this change makes no visible difference.

ldionne · 2026-08-28T11:14:38Z

Pinging @llvm/libcxx-vendors for awareness.

ldionne requested a review from philnik777 August 26, 2026 17:14

ldionne requested review from a team as code owners August 26, 2026 17:14

llvmorg-github-actions Bot added libc++ libc++ C++ Standard Library. Not GNU libstdc++. Not libc++abi. libc++abi libc++abi C++ Runtime Library. Not libc++. backend:AMDGPU labels Aug 26, 2026

ldionne added 2 commits August 26, 2026 13:22

Forgotten change in cross-linux-toolchain

6550ded

update FreeBSD cache

5ca4268

ldionne commented Aug 26, 2026

View reviewed changes

Undo unintended potentially-breaking change

43e218a

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[runtimes] Never define operator new in libc++ - #218989

[runtimes] Never define operator new in libc++#218989
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