demumble demangles both POSIX and Visual Studio symbols. It runs on both POSIX and Windows.

$ ./demumble _Z4funcPci
func(char*, int)
$ ./demumble "?Fx_i@@YAHP6AHH@Z@Z"
int __cdecl Fx_i(int (__cdecl*)(int))

There are prebuilt x64 binaries for Linux, Mac (10.9+), and Windows on the releases page.

It has several nice features that c++filt lacks (and lacks many of c++filt's features I never use).

Smart about underscores: C++ symbols have an additional leading underscore on OS X. operator new is mangled as _Znw on Linux but __Znw on Mac. OS X's c++filt automatically strips one leading underscore, but Linux's c++filt doesn't. So if you want to demangle a Linux symbol on OS X, you need to pass -n to tell it to not strip the underscore, and if you want to demangle an OS X symbol on Linux you likewise need to pass -_. demumble just does the right thing:

$ c++filt _Znw
_Znw
$ c++filt __Znw
operator new
$ demumble _Znw
operator new
$ demumble __Znw
operator new

Smart about filtering: Both c++filt and demumble can work as a stdin filter. demumble only demangles function symbols (which never look like other words), while c++filt defaults to demangling type names too, which are likely to look like regular words. demumble does demangle types when they're passed as args:

$ echo 'I like Pi and _Znw' | c++filt
I like int* and _Znw
$ echo 'I like Pi and _Znw' | demumble
I like Pi and operator new
$ c++filt Pi
int*
$ demumble Pi
int*

Cross-platform: demumble runs on Windows. demumble can demangle Windows-style symbols (also when running on non-Windows).

$ demumble '??2@YAPEAX_K@Z'
void * __ptr64 __cdecl operator new(unsigned __int64)
$ c++filt '??2@YAPEAX_K@Z'
??2@YAPEAX_K@Z

demumble also has a flag to make it print only things that look like symbols. For example, print demangled names of all functions defined in a bitcode file:

$ grep '^define' bitcode-win.ll  | demumble -m | head -1
unsigned int __cdecl v8::RoundUpToPowerOfTwo32(unsigned int)

Use cmake to build: cmake -G Ninja && ninja

Run tests after building: python demumble_test.py

cxa_demangle.cpp needs more C++11 than Visual Studio 2013 supports, so to build on Windows you need to use Visual Studion 2015 or use clang-cl as C++ compiler like so:

cmake -G Ninja -DCMAKE_CXX_COMPILER=path/to/llvm-build/bin/clang-cl.exe