From 19fcec84d8d7d21e796c7624e521b60d28ee21ed Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 20:45:59 +0200 Subject: Adding upstream version 16.2.11+ds. Signed-off-by: Daniel Baumann --- src/fmt/test/fuzzing/README.md | 48 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) create mode 100644 src/fmt/test/fuzzing/README.md (limited to 'src/fmt/test/fuzzing/README.md') diff --git a/src/fmt/test/fuzzing/README.md b/src/fmt/test/fuzzing/README.md new file mode 100644 index 000000000..8f7a4536e --- /dev/null +++ b/src/fmt/test/fuzzing/README.md @@ -0,0 +1,48 @@ +# FMT Fuzzer + +Fuzzing has revealed [several bugs](https://github.com/fmtlib/fmt/issues?&q=is%3Aissue+fuzz) +in fmt. It is a part of the continous fuzzing at +[oss-fuzz](https://github.com/google/oss-fuzz). + +The source code is modified to make the fuzzing possible without locking up on +resource exhaustion: +```cpp +#ifdef FMT_FUZZ +if(spec.precision>100000) { + throw std::runtime_error("fuzz mode - avoiding large precision"); +} +#endif +``` +This macro `FMT_FUZZ` is enabled on OSS-Fuzz builds and makes fuzzing +practically possible. It is used in fmt code to prevent resource exhaustion in +fuzzing mode. +The macro `FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION` is the +defacto standard for making fuzzing practically possible to disable certain +fuzzing-unfriendly features (for example, randomness), see [the libFuzzer +documentation](https://llvm.org/docs/LibFuzzer.html#fuzzer-friendly-build-mode). + +## Running the fuzzers locally + +There is a [helper script](build.sh) to build the fuzzers, which has only been +tested on Debian and Ubuntu linux so far. There should be no problems fuzzing on +Windows (using clang>=8) or on Mac, but the script will probably not work out of +the box. + +Something along +```sh +mkdir build +cd build +export CXX=clang++ +export CXXFLAGS="-fsanitize=fuzzer-no-link -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION= -g" +cmake .. -DFMT_SAFE_DURATION_CAST=On -DFMT_FUZZ=On -DFMT_FUZZ_LINKMAIN=Off -DFMT_FUZZ_LDFLAGS="-fsanitize=fuzzer" +cmake --build . +``` +should work to build the fuzzers for all platforms which clang supports. + +Execute a fuzzer with for instance +```sh +cd build +export UBSAN_OPTIONS=halt_on_error=1 +mkdir out_chrono +bin/fuzzer_chrono_duration out_chrono +``` -- cgit v1.2.3