Drop libc++ (USE_LIBCXX) support (#7850)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: achamayou <4016369+achamayou@users.noreply.github.com>
Co-authored-by: Amaury Chamayou <amchamay@microsoft.com>
Co-authored-by: Amaury Chamayou <amaury@xargs.fr>

Author: Copilot

.github/workflows/long-test.yml

@@ -172,16 +172,13 @@ jobs:
         run: |
           set -ex
           ./scripts/setup-ci.sh
-          # This run requires libc++ to run with hardening mode
-          tdnf -y install libcxx-devel libunwind-devel
 
       - name: "Build"
         run: |
           git config --global --add safe.directory /__w/CCF/CCF
           mkdir build
           cd build
-          # Use libc++ to enable hardening/bounds checking during tests
-          cmake -GNinja -DCMAKE_BUILD_TYPE=Debug -DLONG_TESTS=ON -DUSE_LIBCXX=ON -DUSE_SNMALLOC=OFF ..
+          cmake -GNinja -DCMAKE_BUILD_TYPE=Debug -DGLIBCXX_DEBUG=ON -DLONG_TESTS=ON ..
           ninja
 
       - name: "Test"
@@ -197,7 +194,7 @@ jobs:
           mkdir -p build_fuzz
           cd build_fuzz
           rm -f CMakeCache.txt
-          cmake -GNinja -DFUZZING=ON -DSAN=ON -DUSE_LIBCXX=ON -DUSE_SNMALLOC=OFF ..
+          cmake -GNinja -DFUZZING=ON -DSAN=ON -DUSE_SNMALLOC=OFF ..
           ninja cbor_fuzz_test
           mkdir -p /tmp/cbor_fuzz_live
           ./cbor_fuzz_test /tmp/cbor_fuzz_live ../src/crypto/test/cbor_fuzz_corpus -max_total_time=60

CHANGELOG.md

@@ -9,13 +9,18 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 [7.0.3]: https://github.com/microsoft/CCF/releases/tag/ccf-7.0.3
 
-### Fixed
+### Added
 
-- On a joiner's first attempt, the primary now requires the joiner's startup seqno to be at least as recent as the primary's latest committed snapshot on disk, preventing snapshot-less joiners from replaying the entire ledger (#7844).
+- Added a `GLIBCXX_DEBUG` CMake option to enable libstdc++ debug mode (`_GLIBCXX_DEBUG`) for CCF and its tests. When set, end-to-end tests run via `ConcurrentRunner` are throttled to fewer parallel suites to compensate for the slower runtime, and the `submit` binary (which links against Arrow) is disabled because Arrow is not built with `_GLIBCXX_DEBUG` (#7850).
+
+### Removed
+
+- The `USE_LIBCXX` CMake option and all associated libc++/libc++abi build and packaging support have been removed. CCF now builds exclusively with libstdc++ (#7850).
 
 ### Changed
 
 - Upgraded QuickJS from 2024-01-13 to 2025-09-13 (#7849).
+- On a joiner's first attempt, the primary now requires the joiner's startup seqno to be at least as recent as the primary's latest committed snapshot on disk, preventing snapshot-less joiners from replaying the entire ledger (#7844).
 
 ## [7.0.2]
 

CMakeLists.txt

@@ -93,10 +93,17 @@ option(LONG_TESTS "Enable long end-to-end tests" OFF)
 option(USE_SNMALLOC "Link against snmalloc" ON)
 include(${CMAKE_CURRENT_SOURCE_DIR}/cmake/snmalloc.cmake)
 
-# Useful for debugging with libc++ hardening options
-option(USE_LIBCXX "Use libc++ instead of libstdc++" OFF)
-
 option(CLANG_TIDY "Run clang-tidy on the codebase" OFF)
+
+option(
+  GLIBCXX_DEBUG
+  "Enable libstdc++ debug mode (_GLIBCXX_DEBUG). Disables the submit binary (which links against Arrow, not built with _GLIBCXX_DEBUG)."
+  OFF
+)
+if(GLIBCXX_DEBUG)
+  add_compile_definitions(_GLIBCXX_DEBUG)
+endif()
+
 # Must happen before tools.cmake is included
 if(CLANG_TIDY)
   find_program(
@@ -198,7 +205,6 @@ add_ccf_static_library(
     ${TLS_LIBRARY}
     ${CMAKE_DL_LIBS}
     ${CMAKE_THREAD_LIBS_INIT}
-    ${LINK_LIBCXX}
     ccfcrypto
     curl
     http_parser
@@ -291,12 +297,6 @@ add_ccf_static_library(
     ${CCF_DIR}/src/tasks/worker.cpp
 )
 target_link_libraries(ccf_tasks PRIVATE ${CMAKE_DL_LIBS})
-if(USE_LIBCXX)
-  # worker.cpp uses backtrace() which, under libc++, resolves through libunwind.
-  # On systems where libunwind is built with LZMA support (e.g. Azure Linux),
-  # this creates a transitive dependency on liblzma.
-  target_link_libraries(ccf_tasks PRIVATE lzma)
-endif()
 
 # Common test args for Python scripts starting up CCF networks
 set(
@@ -420,7 +420,6 @@ add_ccf_static_library(
   ccf
   SRCS ${CCF_IMPL_SOURCE}
   LINK_LIBS
-    ${LINK_LIBCXX}
     http_parser
     ccf_js
     ccf_endpoints
@@ -901,10 +900,9 @@ if(BUILD_TESTS)
       src/node/test/merkle_mem.cpp
       ${CCF_DIR}/src/enclave/thread_local.cpp
     )
-    target_compile_options(merkle_mem PRIVATE ${COMPILE_LIBCXX})
     target_link_libraries(
       merkle_mem
-      PRIVATE ${CMAKE_THREAD_LIBS_INIT} ${LINK_LIBCXX} ccfcrypto
+      PRIVATE ${CMAKE_THREAD_LIBS_INIT} ccfcrypto
     )
 
     # Raft driver and scenario test
@@ -941,7 +939,7 @@ if(BUILD_TESTS)
     )
   endif()
 
-  if(NOT TSAN AND NOT USE_LIBCXX)
+  if(NOT TSAN)
     # Picobench benchmarks
     add_picobench(map_bench SRCS src/ds/test/map_bench.cpp)
     add_picobench(logger_bench SRCS src/ds/test/logger_bench.cpp)
@@ -1433,7 +1431,7 @@ install(
   DESTINATION ${CMAKE_INSTALL_PREFIX}/cmake
 )
 
-if(NOT USE_LIBCXX)
-  # Perf tool executable
+# Perf tool executable (requires Arrow/Parquet, not compatible with GLIBCXX_DEBUG)
+if(NOT GLIBCXX_DEBUG)
   include(${CCF_DIR}/tests/perf-system/submitter/CMakeLists.txt)
 endif()

cmake/ccf_app.cmake

@@ -1,17 +1,6 @@
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the Apache 2.0 License.
 
-if(USE_LIBCXX)
-  list(APPEND COMPILE_LIBCXX -stdlib=libc++)
-  list(APPEND LINK_LIBCXX -lc++ -lc++abi -stdlib=libc++)
-
-  if("${CMAKE_BUILD_TYPE}" STREQUAL "Debug")
-    add_compile_options(-D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_DEBUG)
-  elseif("${CMAKE_BUILD_TYPE}" STREQUAL "Release")
-    add_compile_options(-D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_FAST)
-  endif()
-endif()
-
 # Enclave library wrapper
 function(add_ccf_app name)
   cmake_parse_arguments(
@@ -74,9 +63,7 @@ function(add_ccf_static_library name)
 
   add_library(${name} STATIC ${PARSED_ARGS_SRCS})
 
-  target_link_libraries(${name} PUBLIC ${PARSED_ARGS_LINK_LIBS} ${LINK_LIBCXX})
-
-  target_compile_options(${name} PUBLIC ${COMPILE_LIBCXX})
+  target_link_libraries(${name} PUBLIC ${PARSED_ARGS_LINK_LIBS})
 
   set_property(TARGET ${name} PROPERTY POSITION_INDEPENDENT_CODE ON)
 

cmake/common.cmake

@@ -29,13 +29,12 @@ endfunction()
 # Unit test wrapper
 function(add_unit_test name)
   add_executable(${name} ${CCF_DIR}/src/enclave/thread_local.cpp ${ARGN})
-  target_compile_options(${name} PRIVATE ${COMPILE_LIBCXX})
   target_include_directories(
     ${name}
     PRIVATE src ${CCFCRYPTO_INC} ${CCF_DIR}/3rdparty/test
   )
   enable_coverage(${name})
-  target_link_libraries(${name} PRIVATE ${LINK_LIBCXX} ccfcrypto -pthread)
+  target_link_libraries(${name} PRIVATE ccfcrypto -pthread)
   add_san(${name})
 
   add_test(NAME ${name} COMMAND ${name})
@@ -52,33 +51,42 @@ function(add_unit_test name)
   add_san_test_properties(${name})
 endfunction()
 
-# Fuzz test wrapper (requires -DFUZZING=ON -DUSE_LIBCXX=ON)
+# Fuzz test wrapper (requires -DFUZZING=ON)
 function(add_fuzz_test name)
-  if(NOT USE_LIBCXX)
-    message(
-      FATAL_ERROR
-      "Fuzz targets require USE_LIBCXX=ON to avoid UBSAN false positives from libstdc++ shared_ptr"
-    )
-  endif()
-
   add_executable(${name} ${CCF_DIR}/src/enclave/thread_local.cpp ${ARGN})
-  target_compile_options(${name} PRIVATE ${COMPILE_LIBCXX} -fsanitize=fuzzer)
+  target_compile_options(${name} PRIVATE -fsanitize=fuzzer)
   target_link_options(${name} PRIVATE -fsanitize=fuzzer)
   target_include_directories(${name} PRIVATE src ${CCFCRYPTO_INC})
-  target_link_libraries(${name} PRIVATE ${LINK_LIBCXX} -pthread)
+  target_link_libraries(${name} PRIVATE -pthread)
   add_san(${name})
+  # UBSan's vptr check fires inside libstdc++'s
+  # std::_Sp_counted_ptr_inplace<T,A,_Lp>::_Sp_counted_ptr_inplace ctor
+  # (used by std::make_shared) when the inplace control block is being
+  # constructed: that ctor reinterpret_casts uninitialised memory to T*
+  # in order to call std::allocator_traits<T>::construct, and UBSan reads
+  # whatever bytes happen to be there as a vptr. The same false positive
+  # is documented and explicitly excluded by CFI in
+  # compiler-rt/lib/cfi/cfi_ignorelist.txt
+  # (entry: "fun:_ZNSt23_Sp_counted_ptr_inplace*"); UBSan has no
+  # equivalent ignorelist for vptr. See LLVM issue #48337 for context.
+  # The diagnostic is reliably reproducible when libclang_rt.fuzzer is
+  # linked in, because libfuzzer's allocator activity leaves non-zero
+  # bytes in the freshly returned heap slot.
+  # Fuzz binaries don't exercise vtable correctness, so disabling vptr
+  # is the simplest workaround.
+  target_compile_options(${name} PRIVATE -fno-sanitize=vptr)
+  target_link_options(${name} PRIVATE -fno-sanitize=vptr)
 endfunction()
 
 # Test binary wrapper
 function(add_test_bin name)
   add_executable(${name} ${CCF_DIR}/src/enclave/thread_local.cpp ${ARGN})
-  target_compile_options(${name} PRIVATE ${COMPILE_LIBCXX})
   target_include_directories(
     ${name}
     PRIVATE src ${CCFCRYPTO_INC} ${CCF_DIR}/3rdparty/test
   )
   enable_coverage(${name})
-  target_link_libraries(${name} PRIVATE ${LINK_LIBCXX} ccfcrypto)
+  target_link_libraries(${name} PRIVATE ccfcrypto)
   add_san(${name})
 endfunction()
 
@@ -135,6 +143,14 @@ function(add_e2e_test)
       )
     endif()
 
+    if(GLIBCXX_DEBUG)
+      set_property(
+        TEST ${PARSED_ARGS_NAME}
+        APPEND
+        PROPERTY ENVIRONMENT "CCF_GLIBCXX_DEBUG=1"
+      )
+    endif()
+
     if("${PARSED_ARGS_LABEL}" STREQUAL "partitions")
       set_property(
         TEST ${PARSED_ARGS_NAME}

cmake/cpack_ccfapp.cmake

@@ -16,9 +16,5 @@ set(
   CCF_RPM_DEPENDENCIES
   "${CCF_RPM_DEPENDENCIES}, curl >= ${CURL_MINIMAL_VERSION}"
 )
-set(
-  CCF_RPM_DEPENDENCIES
-  "${CCF_RPM_DEPENDENCIES}, libcxxabi >= ${CLANG_AND_LIBCXXABI_MINIMAL_VERSION}"
-)
 
 set(CPACK_CCF_RUNTIME_REQUIRES "${CCF_RPM_DEPENDENCIES}")

cmake/cpack_settings.cmake

@@ -34,12 +34,12 @@ set(
 # + build toolchain
 set(
   CCF_RPM_DEPENDENCIES
-  "${CCF_RPM_DEPENDENCIES}, cmake >= 3.21, build-essential >= 3.0, clang >= ${CLANG_AND_LIBCXXABI_MINIMAL_VERSION}, ninja-build >= 1.11.1"
+  "${CCF_RPM_DEPENDENCIES}, cmake >= 3.21, build-essential >= 3.0, clang >= ${CLANG_MINIMAL_VERSION}, ninja-build >= 1.11.1"
 )
 # + runtime dependencies
 set(
   CCF_RPM_DEPENDENCIES
-  "${CCF_RPM_DEPENDENCIES}, libuv-devel >= ${LIBUV_MINIMAL_VERSION}, curl-devel >= ${CURL_MINIMAL_VERSION}, libcxxabi-devel >= ${CLANG_AND_LIBCXXABI_MINIMAL_VERSION}"
+  "${CCF_RPM_DEPENDENCIES}, libuv-devel >= ${LIBUV_MINIMAL_VERSION}, curl-devel >= ${CURL_MINIMAL_VERSION}"
 )
 # + alter name
 set(CPACK_PACKAGE_NAME "${CPACK_PACKAGE_NAME}_devel")

cmake/cpack_versions_pin.cmake

@@ -5,4 +5,4 @@ set(OPENSSL_MINIMAL_VERSION "3.3.0")
 set(NGHTTP2_MINIMAL_VERSION "1.40.0")
 set(LIBUV_MINIMAL_VERSION "1.34.2")
 set(CURL_MINIMAL_VERSION "7.68.0")
-set(CLANG_AND_LIBCXXABI_MINIMAL_VERSION "18.1.2")
+set(CLANG_MINIMAL_VERSION "18.1.2")

cmake/crypto.cmake

@@ -36,8 +36,6 @@ find_library(TLS_LIBRARY ssl)
 add_library(ccfcrypto STATIC ${CCFCRYPTO_SRC})
 add_san(ccfcrypto)
 add_tidy(ccfcrypto)
-target_compile_options(ccfcrypto PUBLIC ${COMPILE_LIBCXX})
-target_link_options(ccfcrypto PUBLIC ${LINK_LIBCXX})
 
 target_link_libraries(ccfcrypto PUBLIC crypto ssl evercbor)
 target_link_libraries(