added triangulator fuzzer (#620)

* added triangulator fuzzer

* added easy to use minimizer script

* update readme

* added rounding

CMakeLists.txt

@@ -21,12 +21,25 @@ set(MANIFOLD_PAR "NONE" CACHE STRING "Parallel backend, either \"TBB\" or \"NONE
 set(MANIFOLD_FLAGS "" CACHE STRING "Manifold compiler flags")
 option(MANIFOLD_EXPORT "Build mesh export (via assimp) utility library" OFF)
 option(MANIFOLD_TEST "Enable testing suite" ON)
+# fuzztest is a rather large dependency
+option(MANIFOLD_FUZZ "Enable fuzzing tests" OFF)
 option(MANIFOLD_DEBUG "Enable debug tracing/timing" OFF)
-
 option(MANIFOLD_PYBIND "Build python bindings" ON)
 option(MANIFOLD_CBIND "Build C (FFI) bindings" OFF)
 option(MANIFOLD_JSBIND "Build js binding" ${EMSCRIPTEN})
 
+if(MANIFOLD_FUZZ)
+  if(NOT CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    message(FATAL_ERROR "fuzztest only supports clang" )
+  endif()
+  # we should enable debug checks
+  set(MANIFOLD_DEBUG ON)
+  # enable fuzztest fuzzing mode
+  set(FUZZTEST_FUZZING_MODE ON)
+  # address sanitizer required
+  set(CMAKE_CXX_FLAGS "$CMAKE_CXX_FLAGS -fsanitize=address")
+endif()
+
 option(TRACY_ENABLE "Use tracy profiling" OFF) 
 option(TRACY_MEMORY_USAGE "Track memory allocation with tracy (expensive)" OFF)
 option(BUILD_TEST_CGAL "Build CGAL performance comparisons" OFF)

README.md

@@ -140,11 +140,22 @@ For more detailed documentation, please refer to the C++ API.
 
 Contributions are welcome! A lower barrier contribution is to simply make a PR that adds a test, especially if it repros an issue you've found. Simply name it prepended with DISABLED_, so that it passes the CI. That will be a very strong signal to me to fix your issue. However, if you know how to fix it yourself, then including the fix in your PR would be much appreciated!
 
-## Profiling
+### Profiling
 
 There is now basic support for the [Tracy profiler](https://github.com/wolfpld/tracy) for our tests.
 To enable tracing, compile with `-DTRACY_ENABLE=on` cmake option, and run the test with Tracy server running.
 
+### Fuzzing Support
+
+We use https://github.com/google/fuzztest for fuzzing the triangulator.
+
+To enable fuzzing, make sure that you are using clang compiler (`-DCMAKE_CXX_COMPILER=clang -DCMAKE_C_COMPILER=clang`), running Linux, and enable fuzzing support by setting `-DMANIFOLD_FUZZ=ON`.
+
+To run the fuzzer and minimize testcase, do
+```
+../minimizer.sh ./test/polygon_fuzz --fuzz=PolygonFuzz.TriangulationNoCrash
+```
+
 ## About the author
 
 This library was started by [Emmett Lalish](https://elalish.blogspot.com/). I am currently a Google employee and this is my 20% project, not an official Google project. At my day job I'm the maintainer of [\<model-viewer\>](https://modelviewer.dev/). I was the first employee at a 3D video startup, [Omnivor](https://www.omnivor.io/), and before that I worked on 3D printing at Microsoft, including [3D Builder](https://www.microsoft.com/en-us/p/3d-builder/9wzdncrfj3t6?activetab=pivot%3Aoverviewtab). Originally an aerospace engineer, I started at a small DARPA contractor doing seedling projects, one of which became [Sea Hunter](https://en.wikipedia.org/wiki/Sea_Hunter). I earned my doctorate from the University of Washington in control theory and published some [papers](https://www.researchgate.net/scientific-contributions/75011026_Emmett_Lalish).

minimizer.sh

@@ -0,0 +1,59 @@
+#!/usr/bin/env bash
+
+# Modified from https://github.com/google/fuzztest/blob/main/tools/minimizer.sh
+# If you want to use a specific reproducer, pass it in FUZZTEST_MINIMIZE_REPRODUCER
+# environment variable.
+# Otherwise, just run it as
+# $ ./minimizer.sh ./build/test/polygon_fuzz --fuzz=PolygonFuzz.TriangulationNoCrash
+# If you want to kill it, try SIGKILL, SIGTERM is not very useful
+# If you want to end the loop early, rename $(pwd)/reproducers into something
+# else...
+
+if [ -z "${FUZZTEST_MINIMIZE_REPRODUCER}"]; then
+  mkdir -p $(pwd)/reproducers
+  FUZZTEST_REPRODUCERS_OUT_DIR=$(pwd)/reproducers "$@"
+  wildcard="$(pwd)/reproducers/*"
+  reproducers=($wildcard)
+  FUZZTEST_MINIMIZE_REPRODUCER="${reproducers[0]}"
+fi
+readonly ORIGINAL_REPRODUCER="${FUZZTEST_MINIMIZE_REPRODUCER}"
+
+for i in {0001..9999}; do
+  echo
+  echo "╔════════════════════════════════════════════════╗"
+  echo "║ Minimization round: ${i}                       ║"
+  echo "╚════════════════════════════════════════════════╝"
+  echo "Note that to terminate early, simply move $ORIGINAL_REPRODUCER to somewhere else..."
+  echo
+
+  if [ ! -f $ORIGINAL_REPRODUCER ]; then
+    echo "Terminated by the user"
+    break
+  fi
+
+  TEMP_DIR=$(mktemp -d)
+  FUZZTEST_REPRODUCERS_OUT_DIR="${TEMP_DIR}" \
+  FUZZTEST_MINIMIZE_REPRODUCER="${FUZZTEST_MINIMIZE_REPRODUCER}" \
+  "$@"
+
+  if [ $? -eq 130 ]; then
+    echo
+    echo "╔═══════════════════════════════════════════════╗"
+    echo "║ Minimization terminated.                      ║"
+    echo "╚═══════════════════════════════════════════════╝"
+    echo
+    echo "Find the smallest reproducer at:"
+    echo
+    echo "${FUZZTEST_MINIMIZE_REPRODUCER}"
+
+    rm -rf "${TEMP_DIR}"
+    break
+  fi
+
+  SMALLER_REPRODUCER=$(find "${TEMP_DIR}" -type f)
+  NEW_NAME="${ORIGINAL_REPRODUCER}-min-${i}"
+  mv "${SMALLER_REPRODUCER}" "${NEW_NAME}"
+  FUZZTEST_MINIMIZE_REPRODUCER="${NEW_NAME}"
+
+  rm -rf "${TEMP_DIR}"
+done

test/CMakeLists.txt

@@ -14,6 +14,7 @@
 
 project(manifold_test)
 
+set(CMAKE_CXX_STANDARD 17)
 enable_testing()
 
 set(SOURCE_FILES polygon_test.cpp cross_section_test.cpp manifold_test.cpp boolean_test.cpp sdf_test.cpp samples_test.cpp test_main.cpp)
@@ -44,6 +45,21 @@ endif()
 add_executable(${PROJECT_NAME} ${SOURCE_FILES})
 target_link_libraries(${PROJECT_NAME} polygon GTest::gtest_main manifold sdf samples cross_section)
 
+if(MANIFOLD_FUZZ)
+  FetchContent_Declare(fuzztest
+    GIT_REPOSITORY https://github.com/google/fuzztest.git
+    # note that if commit hash is used, it cannot be a shallow clone
+    GIT_TAG        2606e04a43e5a7730e437a849604a61f1cb0ff28
+    GIT_PROGRESS   TRUE
+  )
+  FetchContent_MakeAvailable(fuzztest)
+  fuzztest_setup_fuzzing_flags()
+  add_executable(polygon_fuzz polygon_fuzz.cpp)
+  target_link_libraries(polygon_fuzz PUBLIC polygon)
+  link_fuzztest(polygon_fuzz)
+  gtest_discover_tests(polygon_fuzz)
+endif()
+
 if(MANIFOLD_CBIND)
   target_link_libraries(${PROJECT_NAME} manifoldc)
 endif()