[lldb/Fuzzer] Have fuzzers write artifacts to specific directory

[cassanova]

Summary

This makes the LLDB fuzzers write their fuzzer artifacts to their own directory in the build directory. It also adds an artifact prefix to the target fuzzer to make it easier to tell which fuzzer wrote the artifact.

[JDevlieghere]

Instead of bundling together multiple shell commands into a single one, you should break them down so CMake can have the build system (e.g. ninja) schedule the different parts of it.

To create the directory, you can either create a separate target and make the fuzz-lldb-target depend on it:

add_custom_target(foo ALL
    COMMAND ${CMAKE_COMMAND} -E make_directory ${directory})

But even better would. be to make it a pre-build command for the fuzz-lldb-target:

add_custom_command(TARGET fuzz-lldb-target PRE_BUILD COMMAND ${CMAKE_COMMAND} -E make_directory ${directory})

Then you can avoid the cd by using the WORKING_DIRECTORY in add_custom_target.

[cassanova]

This is a lot cleaner than chaining shell commands, I just implemented the second solution on my end. To clarify, it would create the directory before running the fuzz-lldb-target and within the fuzz-lldb-target we would just change the working directory to the one that the pre-build command created?

[mib]

@cassanova You probably also want to implement this for the command-interpreter-fuzzer target

[cassanova]

Yes, I can include the command interpreter's cmake file in the diff.

[cassanova]

Removed the chain of shell commands in the target fuzzer's CMakeLists file and added a pre build command that creates the necessary directory and changes the working directory in the target to this directory.

Also implemented these changes to the command interpreter fuzzer's CMakeLists file and added it to this diff.

[mib]

This looks way better :) !

lldb/tools/lldb-fuzzer/lldb-commandinterpreter-fuzzer/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   Support
   )
 
 add_llvm_fuzzer(lldb-commandinterpreter-fuzzer
   EXCLUDE_FROM_ALL
   lldb-commandinterpreter-fuzzer.cpp
   )
 
 if(TARGET lldb-commandinterpreter-fuzzer)
   target_include_directories(lldb-commandinterpreter-fuzzer PRIVATE ..)
   target_link_libraries(lldb-commandinterpreter-fuzzer
     PRIVATE
     liblldb
     )
 
-  # This will create a directory specifically for the fuzzer's artifacts, go to that
-  # directory and run the fuzzer from there. When the fuzzer exits the input
-  # artifact that caused it to exit will be written to a directory within the
-  # build directory
+  # A directory in the build directory is created to hold the fuzzer's
+  # artifacts as a pre-build command for the command interpreter's executable
+  # target. When the fuzzer exits the input artifact that caused it to exit
+  # will be written to this directory.
+
+  add_custom_command(TARGET lldb-commandinterpreter-fuzzer PRE_BUILD
+    COMMAND ${CMAKE_COMMAND} -E make_directory ${CMAKE_BINARY_DIR}/fuzzer-artifacts/commandinterpreter-artifacts
+    )
+
   add_custom_target(fuzz-lldb-commandinterpreter
     COMMENT "Running the LLDB command interpreter fuzzer..."
-    COMMAND mkdir -p ${CMAKE_BINARY_DIR}/fuzzer-artifacts/commandinterpreter-artifacts &&
-    cd ${CMAKE_BINARY_DIR}/fuzzer-artifacts/commandinterpreter-artifacts
-    && $<TARGET_FILE:lldb-commandinterpreter-fuzzer> -dict=${CMAKE_CURRENT_SOURCE_DIR}/inputdictionary.txt  -only_ascii=1 -artifact_prefix=commandinterpreter-
+    WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/fuzzer-artifacts/commandinterpreter-artifacts
+    COMMAND  $<TARGET_FILE:lldb-commandinterpreter-fuzzer> -dict=${CMAKE_CURRENT_SOURCE_DIR}/inputdictionary.txt  -only_ascii=1 -artifact_prefix=commandinterpreter-
     USES_TERMINAL
     )
 endif()

lldb/tools/lldb-fuzzer/lldb-target-fuzzer/CMakeLists.txt

 if(TARGET lldb-target-fuzzer)
   target_include_directories(lldb-target-fuzzer PRIVATE ..)
   target_link_libraries(lldb-target-fuzzer
     PRIVATE
     liblldb
     lldbFuzzerUtils
     )
 
+  add_custom_command(TARGET lldb-target-fuzzer PRE_BUILD
+    COMMAND ${CMAKE_COMMAND} -E make_directory ${CMAKE_BINARY_DIR}/fuzzer-artifacts/target-artifacts
+    )
+
   add_custom_target(fuzz-lldb-target
     COMMENT "Running the LLDB target fuzzer..."
-    COMMAND cd ${CMAKE_CURRENT_SOURCE_DIR} && $<TARGET_FILE:lldb-target-fuzzer>
+    WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/fuzzer-artifacts/target-artifacts
+    COMMAND $<TARGET_FILE:lldb-target-fuzzer> -artifact_prefix=target-
     USES_TERMINAL
     )
 endif()