cmake run xxd as custom command - c++

Question

I've a rc directory I want to run xxd -i filename recursively in that directory.and add the generated files to my project.
I was checking some answer on lua. and I did it in a similar way.
SET(RESOURCE_COMPILER "xxd")
SET(COMPILED_RESOURCES "rc/base.css rc/common.js")
FOREACH(F ${COMPILED_RESOURCES})
ADD_CUSTOM_COMMAND(
OUTPUT "${COMPILED_RESOURCES}/${F}"
COMMAND ${RESOURCE_COMPILER} -i "${COMPILED_RESOURCES}/${F}"
COMMENT "Compiling ${F} to binary")
LIST (APPEND COMPILED_RESOURCES "${COMPILED_RESOURCES}/${F}")
ENDFOREACH()
but I don't see any file generated at all.

Answer 1

There are a couple of reasons you may not be seeing the output files. Your xxd command isn't well formed in the add_custom_command, but also the command will only be executed if the output file is required as a source in another CMake target (exe or lib) in the same CMakeLists.txt.
I'd change your snippet to something like:
SET(RESOURCE_COMPILER xxd)
FILE(GLOB_RECURSE COMPILED_RESOURCES "rc/*")
FOREACH(INPUT_FILE ${COMPILED_RESOURCES})
SET(OUTPUT_FILE ${INPUT_FILE}.hex)
ADD_CUSTOM_COMMAND(
OUTPUT ${OUTPUT_FILE}
COMMAND ${RESOURCE_COMPILER} -i ${INPUT_FILE} ${OUTPUT_FILE}
COMMENT "Compiling ${INPUT_FILE} to binary")
LIST(APPEND COMPILED_RESOURCES ${OUTPUT_FILE})
ENDFOREACH()
Then if you have another target which depends on the ${OUTPUT_FILE}s the command will be executed when that target is being built:
ADD_EXECUTABLE(MY_EXE main.cc ${COMPILED_RESOURCES})