add required lib if UMF_BUILD_FUZZTESTS is set

Author: bratpiorka

.github/workflows/nightly.yml

@@ -36,13 +36,20 @@ jobs:
           sudo apt-get update
           sudo apt-get install -y cmake hwloc libhwloc-dev libnuma-dev libtbb-dev
 
+      - name: Find Clang fuzzer lib
+        run: |
+          CLANG_LIBS_DIR=$(find /usr/lib -name "libclang_rt.fuzzer_no_main-x86_64.a" -exec dirname {} \; | head -n 1)
+          echo "CLANG_LIBS_DIR=${CLANG_LIBS_DIR}" >> $GITHUB_ENV
+
       - name: Configure CMake
         run: >
           cmake
           -B ${{github.workspace}}/build
+          -DCMAKE_PREFIX_PATH=${{env.CLANG_LIBS_DIR}}
           -DCMAKE_BUILD_TYPE=${{matrix.build_type}}
           -DCMAKE_C_COMPILER=${{matrix.compiler.c}}
           -DCMAKE_CXX_COMPILER=${{matrix.compiler.cxx}}
+          -DUMF_BUILD_SHARED_LIBRARY=ON
           -DUMF_TESTS_FAIL_ON_SKIP=ON
           -DUMF_DEVELOPER_MODE=ON
           -DUMF_BUILD_FUZZTESTS=ON

CMakeLists.txt

@@ -579,12 +579,29 @@ if(UMF_USE_MSAN)
                     "prevent reporting false-positives")
     add_sanitizer_flag(memory)
 endif()
+
 # Fuzzer instrumentation for the whole library
 if(UMF_BUILD_FUZZTESTS
    AND CMAKE_CXX_COMPILER_ID MATCHES "Clang"
    AND LINUX)
     add_compile_options("-fsanitize=fuzzer-no-link")
     add_link_options("-fsanitize=fuzzer-no-link")
+
+    # We need to find the fuzzer lib in the LLVM installation dir and link it
+    # statically as UMF does not define the main function used by fuzzer as 
+    # well as __sancov_* functions
+    find_library(
+        FUZZER_NO_MAIN_LIB
+        NAMES libclang_rt.fuzzer_no_main-x86_64.a
+    )
+
+    if(FUZZER_NO_MAIN_LIB)
+        message(STATUS "Found fuzzer lib: ${FUZZER_NO_MAIN_LIB}")
+        # Fuzzer lib requires libstdc++
+        link_libraries(${FUZZER_NO_MAIN_LIB} "stdc++")
+    else()
+        message(FATAL_ERROR "libclang_rt.fuzzer_no_main-x86_64 not found!")
+    endif()
 endif()
 
 # A header-only lib to specify include directories in transitive dependencies

README.md

@@ -97,6 +97,19 @@ List of sanitizers available on Windows:
 
 Listed sanitizers can be enabled with appropriate [CMake options](#cmake-standard-options).
 
+### Fuzz testing
+
+To enable fuzz testing, the `UMF_BUILD_FUZZTESTS` CMake configuration flag must
+be set to `ON`. Note, that this feature is supported only on Linux and requires
+Clang. Additionally, ensure that the `CMAKE_PREFIX_PATH` includes the directory
+containing the Clang libraries necessary for fuzzing.
+
+Example:
+
+```bash
+cmake -B build -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_BUILD_TYPE=Debug -DUMF_BUILD_FUZZTESTS=ON -DCMAKE_PREFIX_PATH=/path/to/clang/libs
+```
+
 ### CMake standard options
 
 List of options provided by CMake: