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1Itanium Name Demangler Library2==============================3 4Introduction5------------6 7This directory contains the generic itanium name demangler8library. The main purpose of the library is to demangle C++ symbols,9i.e. convert the string "_Z1fv" into "f()". You can also use the CRTP10base ManglingParser to perform some simple analysis on the mangled11name, or (in LLVM) use the opaque ItaniumPartialDemangler to query the12demangled AST.13 14Why are there multiple copies of the this library in the source tree?15---------------------------------------------------------------------16 17The canonical sources are in libcxxabi/src/demangle and some of the18files are copied to llvm/include/llvm/Demangle. The simple reason for19this comes from before the monorepo, and both [sub]projects need to20demangle symbols, but neither can depend on each other.21 22* libcxxabi needs the demangler to implement __cxa_demangle, which is23 part of the itanium ABI spec.24 25* LLVM needs a copy for a bunch of places, and cannot rely on the26 system's __cxa_demangle because it a) might not be available (i.e.,27 on Windows), and b) may not be up-to-date on the latest language28 features.29 30The copy of the demangler in LLVM has some extra stuff that aren't31needed in libcxxabi (ie, the MSVC demangler, ItaniumPartialDemangler),32which depend on the shared generic components. Despite these33differences, we want to keep the "core" generic demangling library34identical between both copies to simplify development and testing.35 36If you're working on the generic library, then do the work first in37libcxxabi, then run libcxxabi/src/demangle/cp-to-llvm.sh. This38script takes as an optional argument the path to llvm, and copies the39changes you made to libcxxabi over. Note that this script just40blindly overwrites all changes to the generic library in llvm, so be41careful.42 43Because the core demangler needs to work in libcxxabi, everything44needs to be declared in an anonymous namespace (see45DEMANGLE_NAMESPACE_BEGIN), and you can't introduce any code that46depends on the libcxx dylib.47 48FIXME: Now that LLVM is a monorepo, it should be possible to49de-duplicate this code, and have both LLVM and libcxxabi depend on a50shared demangler library.51 52Testing53-------54 55The tests are split up between libcxxabi/test/{unit,}test_demangle.cpp, and56llvm/unittests/Demangle. The llvm directory should only get tests for stuff not57included in the core library. In the future though, we should probably move all58the tests to LLVM.59 60It is also a really good idea to run libFuzzer after non-trivial changes, see61libcxxabi/fuzz/cxa_demangle_fuzzer.cpp and https://llvm.org/docs/LibFuzzer.html.62