These functions from C++ ABI are defined in
compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp and are supposed to
replace implementations from libstdc++/libc++abi.
We need to export them similar to why we need to export other
interceptors and TSan runtime functions - e.g. if a dlopen-ed shared
library depends on `__cxa_guard_acquire`, it needs to pick up the
exported definition from the TSan runtime that was linked into the main
executable calling the dlopen()
However, because the `__cxa_guard_` functions don't use traditional
interceptor machinery, they are omitted from the auto-generated
`libclang_rt.tsan.a.syms` files. Fix this by adding them to
tsan.syms.extra file explicitly.
Co-authored-by: Vitaly Buka <vitalybuka@google.com>
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