Add simple fuzz-harness

Author: nathaniel-brough

CMakeLists.txt

@@ -12,6 +12,12 @@ include(${CMAKE_CURRENT_SOURCE_DIR}/cmake/project-defaults.cmake)
 add_subdirectory(yoga)
 add_subdirectory(tests)
 
+option(BUILD_FUZZ_TESTS "Build fuzz tests" OFF)
+
+if ('${CMAKE_CXX_COMPILER_ID}' MATCHES 'Clang' AND  BUILD_FUZZ_TESTS)
+    add_subdirectory(fuzz)
+endif()
+
 # cmake install config
 include(GNUInstallDirs)
 include(CMakePackageConfigHelpers)

fuzz/CMakeLists.txt

@@ -0,0 +1,16 @@
+# If google/oss-fuzz has set the fuzzing engine
+if(DEFINED ENV{LIB_FUZZING_ENGINE})
+    set(FUZZING_ENGINE $ENV{LIB_FUZZING_ENGINE})
+    set(FUZZING_COMPILE_FLAGS "")
+    set(FUZZING_LINK_FLAGS "${FUZZING_ENGINE}")
+else()
+    set(FUZZING_COMPILE_FLAGS "-fsanitize=fuzzer")
+    set(FUZZING_LINK_FLAGS "-fsanitize=fuzzer")
+endif()
+
+add_executable(fuzz_layout fuzz_layout.cpp)
+set_target_properties(fuzz_layout PROPERTIES
+    COMPILE_FLAGS "${FUZZING_COMPILE_FLAGS}"
+    LINK_FLAGS "${FUZZING_LINK_FLAGS}"
+)
+target_link_libraries(fuzz_layout yogacore)

fuzz/fuzz_layout.cpp

@@ -0,0 +1,45 @@
+#include <fuzzer/FuzzedDataProvider.h>
+#include <cstdint>
+#include <yoga/Yoga.h>
+
+YGFlexDirection fuzzed_flex_direction(FuzzedDataProvider &fdp) {
+  return fdp.PickValueInArray({
+    YGFlexDirectionColumn,
+    YGFlexDirectionColumnReverse,
+    YGFlexDirectionRow,
+    YGFlexDirectionRowReverse,
+  });
+}
+
+void FillFuzzedTree(FuzzedDataProvider &fdp, const YGConfigRef &config, const YGNodeRef &root, size_t depth = 0) {
+  constexpr size_t kMaxDepth = 20;
+  constexpr size_t kMaxChildren= 20;
+
+  if(depth > kMaxDepth) {
+    return;
+  }
+  
+  size_t children = fdp.ConsumeIntegralInRange<size_t>(0, kMaxChildren);
+  for(size_t i = 0; i < children; i++) {
+    const YGNodeRef child = YGNodeNewWithConfig(config);
+    YGNodeStyleSetFlexDirection(root, fuzzed_flex_direction(fdp));
+    YGNodeStyleSetWidth(child, fdp.ConsumeFloatingPoint<float>());
+    YGNodeStyleSetGap(child, YGGutterAll, fdp.ConsumeProbability<float>()*100);
+    YGNodeStyleSetHeight(child, fdp.ConsumeFloatingPoint<float>());
+    YGNodeInsertChild(root, child, i);
+    FillFuzzedTree(fdp, config, child, depth + 1);
+  }
+}
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+  FuzzedDataProvider fdp(data,size);
+  const YGConfigRef config = YGConfigNew();
+  const YGNodeRef root = YGNodeNewWithConfig(config);
+  FillFuzzedTree(fdp, config, root);
+  
+  YGNodeCalculateLayout(root, YGUndefined, YGUndefined, YGDirectionLTR);
+  
+  YGNodeFreeRecursive(root);
+  YGConfigFree(config);
+  return 0;
+}