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Save 8 to 17 KB of flash on ESP32 boards - #11629
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CircuitPython never enables CONFIG_COMPILER_CXX_EXCEPTIONS (IDF default n). In that case IDF's cxx component wraps libgcc's unwinder and libstdc++'s throw entry points with stubs that abort, so C++ code such as nvs_flash does not pull in libgcc's unwinder. CircuitPython lists IDF components by hand and left cxx out, so the unwinder was linked anyway. The existing -u __cxx_init_dummy and -u __cxa_guard_dummy flags also matched nothing (ld does not error on an unresolved -u). Add cxx to the component list and pass the same --wrap list as esp-idf/components/cxx/CMakeLists.txt. Linking cxx also brings in cxx_init.cpp, which sets the libstdc++ emergency exception pool to 0. Feather ESP32-C6: 15,872 bytes less flash, 160 bytes less static RAM. Metro ESP32-S3: 8,592 bytes less flash, 32 bytes less static RAM. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
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What
ESP32 boards no longer carry C++ error handling code that can never run.
Why
It frees flash.
C++ exceptions are already off, but the code to handle them was still linked.
nvmsurvives reset, wifi, soft reset_bleioscan, C6 / S3The other boards were built, not run.
Written with Claude Code, which also ran the tests above. I reviewed the code and this description.
🤖 Generated with Claude Code