Fix oss-fuzz build (#256)

Improves fuzzing build

Author: palemieux

CMakeLists.txt

@@ -238,5 +238,13 @@ install(FILES "${CMAKE_BINARY_DIR}/${PROJECT_NAME}.pc"
 if(CMAKE_PROJECT_NAME STREQUAL PROJECT_NAME AND OJPH_BUILD_TESTS)
   enable_testing()
   add_subdirectory(tests)
+endif()
+
+################################################################################################
+# Testing and fuzzing (OJPH_BUILD_FUZZER)
+################################################################################################
+
+if(OJPH_BUILD_FUZZER)
   add_subdirectory(fuzzing)
 endif()
+

docs/fuzzing.md

@@ -1,13 +1,11 @@
 # Fuzzer Target #
 
-Fuzzer targets can be build using the `OJPH_BUILD_FUZZER` build option. The Dockerfile in the `fuzzing directory` allows local testing:
+Fuzzer targets intended for use with [oss-fuzz](https://oss-fuzz.com/) can be build using the `OJPH_BUILD_FUZZER` build option.
+
+The targets can be run locally as follows:
 
 ```sh
-podman build -t openjph-fuzz  -f fuzzing/Dockerfile
-podman run -it --rm -v $(pwd):/app/ojph/ openjph-fuzz bash
-image# mkdir /app/build/
-image# cd /app/build/
-image# cmake /app/ojph -DCMAKE_CXX_FLAGS="-fsanitize=fuzzer,address" -DOJPH_BUILD_FUZZER=ON -DBUILD_SHARED_LIBS=OFF
-image# make
-image# ./fuzzing/ojph_expand_fuzz_target /app/jp2k_test_codestreams/openjph/*.j2c
+cd build
+cmake .. -DOJPH_BUILD_FUZZER=ON
+./fuzzing/ojph_expand_fuzz_target <test case>
 ```

fuzzing/CMakeLists.txt

@@ -1,6 +1,9 @@
+# detect whether we are within the oss fuzz environment
 if(DEFINED ENV{LIB_FUZZING_ENGINE})
+  # if yes, we can link against the main function of the fuzzing engine
   link_libraries($ENV{LIB_FUZZING_ENGINE})
 else()
+  # if not, we need to define our main function
   add_compile_definitions(OJPH_FUZZ_TARGET_MAIN)
 endif()