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- Itanium Name Demangler Library
- ==============================
- Introduction
- ------------
- This directory contains the generic itanium name demangler
- library. The main purpose of the library is to demangle C++ symbols,
- i.e. convert the string "_Z1fv" into "f()". You can also use the CRTP
- base ManglingParser to perform some simple analysis on the mangled
- name, or (in LLVM) use the opaque ItaniumPartialDemangler to query the
- demangled AST.
- Why are there multiple copies of the this library in the source tree?
- ---------------------------------------------------------------------
- The canonical sources are in libcxxabi/src/demangle and some of the
- files are copied to llvm/include/llvm/Demangle. The simple reason for
- this comes from before the monorepo, and both [sub]projects need to
- demangle symbols, but neither can depend on each other.
- * libcxxabi needs the demangler to implement __cxa_demangle, which is
- part of the itanium ABI spec.
- * LLVM needs a copy for a bunch of places, and cannot rely on the
- system's __cxa_demangle because it a) might not be available (i.e.,
- on Windows), and b) may not be up-to-date on the latest language
- features.
- The copy of the demangler in LLVM has some extra stuff that aren't
- needed in libcxxabi (ie, the MSVC demangler, ItaniumPartialDemangler),
- which depend on the shared generic components. Despite these
- differences, we want to keep the "core" generic demangling library
- identical between both copies to simplify development and testing.
- If you're working on the generic library, then do the work first in
- libcxxabi, then run the cp-to-llvm.sh script in src/demangle. This
- script takes as an optional argument the path to llvm, and copies the
- changes you made to libcxxabi over. Note that this script just
- blindly overwrites all changes to the generic library in llvm, so be
- careful.
- Because the core demangler needs to work in libcxxabi, everything
- needs to be declared in an anonymous namespace (see
- DEMANGLE_NAMESPACE_BEGIN), and you can't introduce any code that
- depends on the libcxx dylib.
- FIXME: Now that LLVM is a monorepo, it should be possible to
- de-duplicate this code, and have both LLVM and libcxxabi depend on a
- shared demangler library.
- Testing
- -------
- The tests are split up between libcxxabi/test/{unit,}test_demangle.cpp, and
- llvm/unittest/Demangle. The llvm directory should only get tests for stuff not
- included in the core library. In the future though, we should probably move all
- the tests to LLVM.
- It is also a really good idea to run libFuzzer after non-trivial changes, see
- libcxxabi/fuzz/cxa_demangle_fuzzer.cpp and https://llvm.org/docs/LibFuzzer.html.
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