Pharos Visual C++ Demangler

The Pharos Visual C++ Demangler is a symbol de-mangling tool that demangles C++ symbol names generated by Microsoft Visual C++ in order to retrieve the original C++ declaration. It also includes a JSON output mode which splits the symbols up into their constituent parts for type analysis, etc. It exists both as a standalone program and as a library which linked to by other programs.

Build and Install

cmake is the build tool used for this project. The build has only been tested under Linux, but should be easily adaptable to other systems if needed.

From the top directory of the distribution:

mkdir build
cd build
cmake ..
make
make install

JSON output

There are currently two JSON formats emitted by the command-line tool. Raw and minimal.

The minimal format is only really useful for functions and methods, and outputs the full type names for the argument and return value of these functions. For other symbol types, it will duplicate the raw format.

The raw format was originally written to help debug the demangler. It is a direct JSON representation of the C++ structure that represents the demangled name.

A user-friendly non-minimal JSON output schema has been worked on, but has not been completed. (This is what --json without qualifiers is reserved for as a command-line argument.) Figuring out a happy medium between the raw format and the minimal format is harder than one might think.

Known deficiencies

• C++/CLI symbols are very poorly supported due to both lack of references and lack of a reasonable test corpus

undname differences

When comparing output to undname.exe, the pharos demangler differs in some important places:

• Spacing may be different.
• undname.exe sometimes omits const in places where that const is definitely encoded in the symbol. We've been able to determine that constant pointers have the const elided when used as a return value. Other circumstances exists, though, that we have not been able to figure out.
• In most places undname.exe outputs anonymous namespaces as `anonymous namespace', but sometimes it fails and will output the literal string in the mangled name representing the namespace, such as A0xcfd685c9.
• There are some mangled names that undname.exe just fails completely on that the Pharos demangler either succeeds on or "does better." Any undname result with a ? or a @ in it is considered a failed result.

Python Bindings

The Pharos Visual C++ Demangler may also be compiled as a python module. For either Python 2.7.x or Python 3.4+, from the top directory of the distribution:

python setup.py install

The demangler can now be called from within python scripts by using:

import pydemangler
unmangled = pydemangler.demangle("??SomeMangledFunction")

The python module returns properties of the unmangled function as a python object (dictionary) rather than a JSON string.

State of the code

This code was written to support our own research goals. It was hacked together in a short amount of time, and things were added when needed in a very ad-hoc fashion. Although some time was spent cleaning up code for release, do not expect this to be the cleanest bit of code in the world. In particular, the DemangledType data structure has accumulated members at need.

References

The information we used to create this program came from three primary sources:

• Wikiversity Visual C++ name mangling
• Calling conventions by Agner Fog
• Output from the Microsoft Visual C++ compiler and its undname.exe demangler

Legal

Pharos Demangler

Copyright 2017-2020 Carnegie Mellon University. All Rights Reserved.

NO WARRANTY. THIS CARNEGIE MELLON UNIVERSITY AND SOFTWARE ENGINEERING INSTITUTE MATERIAL IS FURNISHED ON AN "AS-IS" BASIS. CARNEGIE MELLON UNIVERSITY MAKES NO WARRANTIES OF ANY KIND, EITHER EXPRESSED OR IMPLIED, AS TO ANY MATTER INCLUDING, BUT NOT LIMITED TO, WARRANTY OF FITNESS FOR PURPOSE OR MERCHANTABILITY, EXCLUSIVITY, OR RESULTS OBTAINED FROM USE OF THE MATERIAL. CARNEGIE MELLON UNIVERSITY DOES NOT MAKE ANY WARRANTY OF ANY KIND WITH RESPECT TO FREEDOM FROM PATENT, TRADEMARK, OR COPYRIGHT INFRINGEMENT.

Released under a BSD-style license, please see license.txt or contact [email protected] for full terms.

[DISTRIBUTION STATEMENT A] This material has been approved for public release and unlimited distribution. Please see Copyright notice for non-US Government use and distribution.

DM17-0949