add Dockerfile and build script for Folly fuzzing integration

projects/folly/Dockerfile

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+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+################################################################################
+
+FROM gcr.io/oss-fuzz-base/base-builder:ubuntu-24-04
+
+# Build tools and Folly runtime dependencies
+RUN apt-get update && apt-get install -y \
+    cmake \
+    ninja-build \
+    pkg-config \
+    python3 \
+    libboost-all-dev \
+    libssl-dev \
+    libevent-dev \
+    libdouble-conversion-dev \
+    libgflags-dev \
+    libgoogle-glog-dev \
+    libfmt-dev \
+    liblz4-dev \
+    libzstd-dev \
+    libsnappy-dev \
+    libbz2-dev \
+    zlib1g-dev \
+    libunwind-dev \
+    libelf-dev
+
+# Clone the upstream repository; fuzz targets live in folly/fuzz/ inside it.
+RUN git clone --depth 1 https://github.com/facebook/folly.git $SRC/folly
+
+COPY build.sh $SRC/

projects/folly/build.sh

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+#!/bin/bash -eu
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+################################################################################
+#
+# Build script for the Folly OSS-Fuzz integration.
+#
+# Strategy:
+#  1. Build Folly as a static library using CMake + Ninja, honouring the
+#     sanitizer flags injected by the OSS-Fuzz harness ($CC/$CXX/$CFLAGS/
+#     $CXXFLAGS).
+#  2. Compile each fuzz target from folly/fuzz/ directly with $CXX so that
+#     $LIB_FUZZING_ENGINE (the fuzzing-engine flag or library provided by the
+#     OSS-Fuzz harness) is wired in correctly.
+#  3. Install the resulting binaries into $OUT.
+
+readonly FOLLY_SRC="$SRC/folly"
+readonly BUILD_DIR="$FOLLY_SRC/_build"
+readonly FUZZ_SRC="$FOLLY_SRC/folly/fuzz"
+
+mkdir -p "$BUILD_DIR"
+cd "$BUILD_DIR"
+
+# ---------------------------------------------------------------------------
+# Step 1 – build the Folly library
+# ---------------------------------------------------------------------------
+cmake "$FOLLY_SRC" \
+  -G Ninja \
+  -DCMAKE_C_COMPILER="${CC}" \
+  -DCMAKE_CXX_COMPILER="${CXX}" \
+  -DCMAKE_C_FLAGS="${CFLAGS}" \
+  -DCMAKE_CXX_FLAGS="${CXXFLAGS}" \
+  -DCMAKE_CXX_STANDARD=20 \
+  -DCMAKE_BUILD_TYPE=RelWithDebInfo \
+  -DCMAKE_POSITION_INDEPENDENT_CODE=ON \
+  -DBUILD_SHARED_LIBS=OFF \
+  -DFOLLY_USE_JEMALLOC=OFF \
+  -DBUILD_TESTS=OFF \
+  -DBUILD_BENCHMARKS=OFF \
+  -DBUILD_FUZZ_TARGETS=OFF  # fuzz targets compiled separately below
+
+cmake --build . -j"$(nproc)" --target folly
+
+# ---------------------------------------------------------------------------
+# Step 2 – compile and link each fuzz target
+# ---------------------------------------------------------------------------
+
+# The generated folly-config.h lives in the build directory; headers in source.
+INCLUDES="-I${FOLLY_SRC} -I${BUILD_DIR}"
+
+# System libraries that folly depends on (order matters for GNU ld static libs).
+SYS_LIBS="\
+  -lboost_filesystem -lboost_system -lboost_thread -lboost_regex \
+  -lglog -lgflags -lfmt -ldouble-conversion \
+  -lssl -lcrypto -levent \
+  -lsnappy -llz4 -lzstd -lz -lbz2 \
+  -lunwind -lelf \
+  -lpthread -ldl -latomic"
+
+FOLLY_LIB="${BUILD_DIR}/libfolly.a"
+
+for fuzzer_src in "${FUZZ_SRC}"/*_fuzzer.cc; do
+  fuzzer_name="$(basename "${fuzzer_src%.cc}")"
+  echo "Building ${fuzzer_name} ..."
+  "$CXX" $CXXFLAGS -std=c++20 \
+    $INCLUDES \
+    "${fuzzer_src}" \
+    $LIB_FUZZING_ENGINE \
+    -Wl,--start-group "${FOLLY_LIB}" -Wl,--end-group \
+    $SYS_LIBS \
+    -o "${OUT}/${fuzzer_name}"
+
+  # Package the seed corpus if a corpus directory exists for this target.
+  corpus_dir="${FUZZ_SRC}/corpus/${fuzzer_name}"
+  if [[ -d "${corpus_dir}" ]]; then
+    zip -j "${OUT}/${fuzzer_name}_seed_corpus.zip" "${corpus_dir}"/*
+  fi
+done

projects/folly/project.yaml

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+homepage: "https://github.com/facebook/folly"
+language: c++
+primary_contact: "yfeldblum@meta.com"
+main_repo: "https://github.com/facebook/folly.git"
+auto_ccs:
+  - "yuxizhangrex@meta.com"
+  - "drollman@meta.com"
+  - "mzlee@meta.com"
+vendor_ccs:
+  - "oss-fuzz@fb.com"
+fuzzing_engines:
+  - libfuzzer
+sanitizers:
+  - address
+  - undefined
+base_os_version: ubuntu-24-04