[libcxx-commits] [libcxx] [libc++][NFC] Clean up atomic_support.h (PR #212464)

Wed Jul 29 08:39:24 PDT 2026

ilovepi wrote:

I think this may be breaking some builds of libcxx, particularly for riscv32. 

Bot: https://ci.chromium.org/ui/p/fuchsia/builders/toolchain.ci/clang-target-riscv32-unknown-elf/b8674941923920199217/overview

Logs: https://logs.chromium.org/logs/fuchsia/buildbucket/cr-buildbucket/8674941923920199217/+/u/build_runtimes/runtimes-riscv32-unknown-elf/build/stdout

```
FAILED: libcxx/src/CMakeFiles/cxx_static.dir/exception.cpp.obj 
/b/s/w/ir/x/w/llvm_build/bin/clang++ --target=riscv32-unknown-elf -DLIBC_NAMESPACE=__llvm_libc_common_utils -DLIBC_THREAD_MODE=LIBC_THREAD_MODE_SINGLE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LIBCPP_AVAILABILITY_MINIMUM_HEADER_VERSION=2 -D_LIBCPP_BUILDING_HAS_NO_ABI_LIBRARY -D_LIBCPP_BUILDING_LIBRARY -D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER -D_LIBCPP_LINK_PTHREAD_LIB -D_LIBCPP_LINK_RT_LIB -D_LIBCPP_REMOVE_TRANSITIVE_INCLUDES -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/b/s/w/ir/x/w/llvm-llvm-project/libcxx/src -I/b/s/w/ir/x/w/llvm_build/bin/include/riscv32-unknown-unknown-elf/c++/v1 -I/b/s/w/ir/x/w/llvm_build/bin/include/c++/v1 -isystem /b/s/w/ir/x/w/llvm_build/bin/include/riscv32-unknown-unknown-elf -isystem /b/s/w/ir/x/w/llvm-llvm-project/cmake/Modules/../../libc --target=riscv32-unknown-elf -march=rv32imc_zicsr_zifencei -mabi=ilp32 -Wno-atomic-alignment -D_LIBCPP_PRINT=1 -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wno-pass-failed -Wmisleading-indentation -Wctad-maybe-unsupported -ffunction-sections -fdata-sections -Xclang -fno-pch-timestamp -ffile-prefix-map=/b/s/w/ir/x/w/llvm_build/runtimes/runtimes-riscv32-unknown-elf=../../../llvm-llvm-project -ffile-prefix-map=/b/s/w/ir/x/w/llvm-llvm-project/= -no-canonical-prefixes -O2 -g -DNDEBUG -std=c++26 -faligned-allocation -nostdinc++ -fvisibility-inlines-hidden -fvisibility=hidden -fsized-deallocation -Wall -Wextra -Wnewline-eof -Wshadow -Wwrite-strings -Wno-unused-parameter -Wno-long-long -Werror=return-type -Wextra-semi -Wundef -Wunused-template -Wformat-nonliteral -Wzero-length-array -Wdeprecated-redundant-constexpr-static-def -Wno-nullability-completeness -Wmissing-prototypes -Wno-user-defined-literals -Wno-covered-switch-default -Wno-suggest-override -Wno-error -fno-exceptions -fno-rtti -fdebug-prefix-map=/b/s/w/ir/x/w/llvm_build/bin/include/c++/v1=/b/s/w/ir/x/w/llvm-llvm-project/libcxx/include -nostdlibinc -MD -MT libcxx/src/CMakeFiles/cxx_static.dir/exception.cpp.obj -MF libcxx/src/CMakeFiles/cxx_static.dir/exception.cpp.obj.d -o libcxx/src/CMakeFiles/cxx_static.dir/exception.cpp.obj -c /b/s/w/ir/x/w/llvm-llvm-project/libcxx/src/exception.cpp
In file included from /b/s/w/ir/x/w/llvm-llvm-project/libcxx/src/exception.cpp:28:
/b/s/w/ir/x/w/llvm-llvm-project/libcxx/src/support/runtime/exception_fallback.ipp:56:2: warning: uncaught_exception not yet implemented [-W#warnings]
   56 | #warning uncaught_exception not yet implemented
      |  ^
/b/s/w/ir/x/w/llvm-llvm-project/libcxx/src/support/runtime/exception_fallback.ipp:68:1: error: use of undeclared identifier 'bad_alloc'
   68 | bad_alloc::bad_alloc() noexcept {}
      | ^
/b/s/w/ir/x/w/llvm-llvm-project/libcxx/src/support/runtime/exception_fallback.ipp:70:1: error: use of undeclared identifier 'bad_alloc'
   70 | bad_alloc::~bad_alloc() noexcept {}
      | ^
/b/s/w/ir/x/w/llvm-llvm-project/libcxx/src/support/runtime/exception_fallback.ipp:72:13: error: use of undeclared identifier 'bad_alloc'
   72 | const char* bad_alloc::what() const noexcept { return "std::bad_alloc"; }
      |             ^
/b/s/w/ir/x/w/llvm-llvm-project/libcxx/src/support/runtime/exception_fallback.ipp:74:1: error: use of undeclared identifier 'bad_array_new_length'
   74 | bad_array_new_length::bad_array_new_length() noexcept {}
      | ^
/b/s/w/ir/x/w/llvm-llvm-project/libcxx/src/support/runtime/exception_fallback.ipp:76:1: error: use of undeclared identifier 'bad_array_new_length'
   76 | bad_array_new_length::~bad_array_new_length() noexcept {}
      | ^
/b/s/w/ir/x/w/llvm-llvm-project/libcxx/src/support/runtime/exception_fallback.ipp:78:13: error: use of undeclared identifier 'bad_array_new_length'
   78 | const char* bad_array_new_length::what() const noexcept { return "bad_array_new_length"; }
      |             ^
In file included from /b/s/w/ir/x/w/llvm-llvm-project/libcxx/src/exception.cpp:29:
/b/s/w/ir/x/w/llvm-llvm-project/libcxx/src/support/runtime/exception_pointer_unimplemented.ipp:16:2: warning: exception_ptr not yet implemented [-W#warnings]
   16 | #warning exception_ptr not yet implemented
      |  ^
/b/s/w/ir/x/w/llvm-llvm-project/libcxx/src/support/runtime/exception_pointer_unimplemented.ipp:21:2: warning: exception_ptr not yet implemented [-W#warnings]
   21 | #warning exception_ptr not yet implemented
      |  ^
/b/s/w/ir/x/w/llvm-llvm-project/libcxx/src/support/runtime/exception_pointer_unimplemented.ipp:26:2: warning: exception_ptr not yet implemented [-W#warnings]
   26 | #warning exception_ptr not yet implemented
      |  ^
/b/s/w/ir/x/w/llvm-llvm-project/libcxx/src/support/runtime/exception_pointer_unimplemented.ipp:31:2: warning: exception_ptr not yet implemented [-W#warnings]
   31 | #warning exception_ptr not yet implemented
      |  ^
/b/s/w/ir/x/w/llvm-llvm-project/libcxx/src/support/runtime/exception_pointer_unimplemented.ipp:44:2: warning: exception_ptr not yet implemented [-W#warnings]
   44 | #warning exception_ptr not yet implemented
      |  ^
/b/s/w/ir/x/w/llvm-llvm-project/libcxx/src/support/runtime/exception_pointer_unimplemented.ipp:54:2: warning: exception_ptr not yet implemented [-W#warnings]
   54 | #warning exception_ptr not yet implemented
      |  ^
/b/s/w/ir/x/w/llvm-llvm-project/libcxx/src/support/runtime/exception_pointer_unimplemented.ipp:59:2: warning: exception_ptr not yet implemented [-W#warnings]
   59 | #warning exception_ptr not yet implemented
      |  ^
8 warnings and 6 errors generated.
```

Could you take a look? 

https://github.com/llvm/llvm-project/pull/212464