Re: [PATCH 00/14] Introduce fuzzing of XML formats

On Tue, Aug 20, 2024 at 03:03:47PM +0100, Daniel P. Berrangé wrote: > On Mon, Aug 19, 2024 at 09:39:38PM +0530, Rayhan Faizel wrote: > > This series introduces multiple fuzzers developed as part of Google Summer > > of Code 2024. We adopt a structure-aware fuzzing approach to fuzz libvirt > > XML formats. The fuzzing methodology makes use of libFuzzer and > > libprotobuf-mutator. The fuzzers work by mutating intermediate protobufs > > and converting them to XML. > > > > The fuzzing method in use requires inclusion of C++ sources. However, C++ > > compilation will be done only if '-Dfuzz' is enabled. Otherwise, libvirt will > > compile normally as before. The fuzzing method works only on clang compilers > > which support libFuzzer. > > Hmm, I wish you'd raised this issue on the list before investing all > this work becasue IMHO the dependency on C++ is not something I would > want to see in the libvirt project, even just for tests. It was a > very delibrate decision that libvirt be a C project, not C++ project, > and if we're going to extend libvirt to take code in any new language > the choices that make sense looking to the future are Rust or Go, > not C++. > That was unfortunate, but since Rayhan had the first implementation done in a very short time we rather spent the rest of the time enhancing the fuzzing and it definitely bore fruit -- some of the found things are fixed, some are still waiting for a patch or two.

The crucial part of this is the existing libprotobuf-mutator which is already in C++ and does provide very specific C++ APIs.

Another approach (except writing our own mutator) would be to keep the code in a separate repository. I'm not completely sure whether we would still need the code modifications, I don't remember our discussions about whether the fuzzing compilation could work with all current libvirt code compiled as C and only the fuzzing parts compiled in C++.