Question about handling of CMAKE_PREFIX_PATH

[mvieth]

Hi, I have a question about the handling of CMAKE_PREFIX_PATH:

catkin/cmake/all.cmake

Lines 42 to 55 in a31d889

	# use either CMAKE_PREFIX_PATH explicitly passed to CMake as a command line argument
	# or CMAKE_PREFIX_PATH from the environment
	if(NOT DEFINED CMAKE_PREFIX_PATH)
	if(NOT "$ENV{CMAKE_PREFIX_PATH}" STREQUAL "")
	if(NOT WIN32)
	string(REPLACE ":" ";" CMAKE_PREFIX_PATH $ENV{CMAKE_PREFIX_PATH})
	else()
	set(CMAKE_PREFIX_PATH $ENV{CMAKE_PREFIX_PATH})
	endif()
	endif()
	endif()
	message(STATUS "Using CMAKE_PREFIX_PATH: ${CMAKE_PREFIX_PATH}")
	# store original CMAKE_PREFIX_PATH
	set(CMAKE_PREFIX_PATH_AS_IS ${CMAKE_PREFIX_PATH})

At the beginning, it is tested whether CMAKE_PREFIX_PATH is not defined. We discovered a problem in perception_pcl (ros-perception/perception_pcl#351) where CMAKE_PREFIX_PATH is defined, but empty. For details, please see there. This problem is fixed now in perception_pcl (at least for ROS 1), but it could potentially appear similarly for other ROS packages, so I wanted to notify you of this behaviour and ask, why it was written this way