Do not intercept JVM-internal C stdlib calls (#45)

* Replace uses of quick_exit and at_quick_exit

quick_exit is not supported on macOS, but can easily replaced by a call
to _Exit after running our cleanup manually.

* Run buildifier --lint=fix -r .

* Build libFuzzer from source

Building libFuzzer from source is easy and has multiple advantages:
* The clang distributed with XCode on macOS does not include libFuzzer.
* Applying a small patch to libFuzzer will allow us to replace the
  --wrap linker feature, which is not supported on platforms other than
  Linux.

* Replace -Wl,--wrap with a source code patch

* Pin non-native rules_python

* Print exit code on test failure

* Do not intercept JVM-internal C stdlib calls

The JVM frequently calls strcmp/memcmp/..., which fills up the table of
recent compares with entries that are either duplicates of values
already reported by the bytecode instrumentation or JDK-internal strings
that are not relevant for fuzzing.

This commit adds an ignorelist to the C stdlib interceptors that filters
out calls from known JVM libraries. If the fuzz target has not yet
loaded a native library, all such callbacks are ignored, which greatly
improves fuzzer performance for string-heavy targets. E.g.,
JsonSanitizerDenylistFuzzer takes < 1 million runs now when it used to
take over 3 million.

1 files changed, 1 insertions, 0 deletions

diff --git a/bazel/fuzz_target_test_wrapper.sh b/bazel/fuzz_target_test_wrapper.sh
index 7a2a9f7f..061ed3ae 100755
--- a/bazel/fuzz_target_test_wrapper.sh
+++ b/bazel/fuzz_target_test_wrapper.sh
@@ -24,5 +24,6 @@ if [ $exit_code -eq 77 ] || [ $exit_code -eq 76 ]
 then
   exit 0
 else
+  echo "Unexpected exit code: $exit_code"
   exit 1
 fi