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libstdc++ selects between a lock-free and a mutex-based policy for std::shared_ptr reference counting based on this macro. Enabling this option forces the lock-free policy, which avoids pulling in the mutex-based implementation and can reduce code size. Note: the lock-free policy avoids embedding a mutex in each control block, saving about 88 bytes per shared_ptr, and improves performance by using atomic operations instead of mutex locking. Note: this option changes the ABI of libstdc++ atomic/shared_ptr helpers. It can be incompatible when linking against prebuilt libraries that were compiled without it, leading to link errors or undefined runtime behavior. Only enable it if all C++ objects and libraries in the build use the same setting.
| Supported Targets | ESP32-C5 |
|---|
C++ atomic lock policy test
Build-only app. Validates CONFIG_COMPILER_CXX_ATOMIC_LOCK_POLICY: both
translation units use std::shared_ptr under the forced lock-free policy, and
the cxx post-build hook accepts the linked executable.
For the negative build-system check (mixed __gnu_cxx::_Lock_policy), see
tools/test_build_system/test_cxx_atomic_policy.py, which builds this app with
-DTEST_INVALID_LOCK_POLICIES=1.