Force __cxa_can_catch in LTO with exceptions - #27578
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During LTO code generation, the LLVM backend lowers Emscripten exception handling into calls to __cxa_find_matching_catch_N, which is provided by JS library code and requires __cxa_can_catch from libc++abi. Because libc++abi is an archive of bitcode files in LTO builds, __cxa_can_catch is not extracted before LTO codegen unless explicitly referenced, leading to undefined symbol errors.
sbc100
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Aug 20, 2026
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During LTO code generation, the LLVM backend lowers Emscripten exception handling into calls to __cxa_find_matching_catch_N, which is provided by JS library code and requires __cxa_can_catch from libc++abi.
Because libc++abi is an archive of bitcode files in LTO builds, __cxa_can_catch is not extracted before LTO codegen unless explicitly referenced, leading to undefined symbol errors.
This is needed after the changes to wasm-ld land.