Skip to content
Branch: master
Find file History
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Type Name Latest commit message Commit time
Failed to load latest commit information.


libnfuzz is a wrapper library that exports to C, a set of fuzzing test cases written in Nim and making use of nim-beacon-chain.


To build the wrapper library (for more details follow first the instructions from nim-beacon-chain):

git clone
cd nim-beacon-chain
# static library
make libnfuzz.a
# dynamic loaded library

Default, the library is build with the minimal config. To select a specific config you can instead run:

# build with mainnet config
make libnfuzz.a NIMFLAGS="-d:const_preset=mainnet"

For the library to be useful for fuzzing with libFuzzer (e.g. for integration with beacon-fuzz) we can pass additional Nim arguments, e.g.:

make libnfuzz.a NIMFLAGS="--cc:clang --passC:'-fsanitize=fuzzer-no-link' --passL='-fsanitize=fuzzer'"

To disable BLS verification on deserialization of SSZ objects add -d:ssz_testing to the NIMFLAGS.

Other useful options might include: --clang.path:<path>, --clang.exe:<exe>, --clang.linkerexe:<exe>, -d:const_preset=mainnet

It might also deem useful to lower the log level, e.g. by adding -d:chronicles_log_level=fatal.


There is a libnfuzz.h file provided for easy including in C or C++ projects.

It is most important that before any of the exported tests are called, the NimMain() call is done first. Additionally, all following library calls need to be done from the same thread as from where the original NimMain() call was done.

You can’t perform that action at this time.