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borg/scripts/fuzz-cache-sync/HOWTO
Marian Beermann c786a5941e CacheSynchronizer: redo as quasi FSM on top of unpack.h
This is a (relatively) simple state machine running in the
data callbacks invoked by the msgpack unpacking stack machine
(the same machine is used in msgpack-c and msgpack-python,
changes are minor and cosmetic, e.g. removal of msgpack_unpack_object,
removal of the C++ template thus porting to C and so on).

Compared to the previous solution this has multiple advantages
- msgpack-c dependency is removed
- this approach is faster and requires fewer and smaller
  memory allocations

Testability of the two solutions does not differ in my
professional opinion(tm).

Two other changes were rolled up; _hashindex.c can be compiled
without Python.h again (handy for fuzzing and testing);
a "small" bug in the cache sync was fixed which allocated too
large archive indices, leading to excessive archive.chunks.d
disk usage (that actually gave me an idea).
2017-06-02 17:43:15 +02:00

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- Install AFL and the requirements for LLVM mode (see docs)
- Compile the fuzzing target, e.g.
AFL_HARDEN=1 afl-clang-fast main.c -o fuzz-target -O3
(other options, like using ASan or MSan are possible as well)
- Add additional test cases to testcase_dir
- Run afl, easiest (but inefficient) way;
afl-fuzz -i testcase_dir -o findings_dir ./fuzz-target