I assume that by βC ++ codeβ you mean something that mutates the source code, not the compiled version? Mutation of the source code is much more difficult to implement than an intermediate mutation of the code (for example, Java bytecode or .NET IL). Because of this, I strongly suspect that you will not find open source.
The challenge is to parse the source code as a syntax tree, a complex C ++ problem that will then allow you to identify mutation points and make the necessary changes to the source code. You can take a look at GCCXML as an open source starting point for parsing - adding a mutation is actually the simpler part of the problem.
The open source NinjaTurtles ( disclaimer: I'm the lead developer on this) will mutate assemblies compiled from .NET C ++ managed code, but I suspect it won't work for you?
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