1# Find the prefix from the `*Config.cmake` file being generated. 2# 3# When generating an installed `*Config.cmake` file, we often want to be able 4# to refer to the ancestor directory which contains all the installed files. 5# 6# We want to do this without baking in an absolute path when the config file is 7# generated, in order to allow for a "relocatable" binary distribution that 8# doesn't need to know what path it ends up being installed at when it is 9# built. 10# 11# The solution that we know the relative path that the config file will be at 12# within that prefix, like `"${prefix_var}/lib/cmake/${project}"`, so we count 13# the number of components in that path to figure out how many parent dirs we 14# need to traverse from the location of the config file to get to the prefix 15# dir. 16# 17# out_var: 18# variable to set the "return value" of the function, which is the code to 19# include in the config file under construction. 20# 21# prefix_var: 22# Name of the variable to define in the returned code (not directory for the 23# faller!) that will contain the prefix path. 24# 25# path_to_leave: 26# Path from the prefix to the config file, a relative path which we wish to 27# go up and out from to find the prefix directory. 28function(find_prefix_from_config out_var prefix_var path_to_leave) 29 if(IS_ABSOLUTE "${path_to_leave}") 30 # Because the path is absolute, we don't care about `path_to_leave` 31 # because we can just "jump" to the absolute path rather than work 32 # our way there relatively. 33 set(config_code 34 "# Installation prefix is fixed absolute path" 35 "set(${prefix_var} \"${CMAKE_INSTALL_PREFIX}\")") 36 else() 37 # `path_to_leave` is relative. Relative to what? The install prefix. 38 # We therefore go up enough parent directories to get back to the 39 # install prefix, and avoid hard-coding any absolute paths. 40 set(config_code 41 "# Compute the installation prefix from this LLVMConfig.cmake file location." 42 "get_filename_component(${prefix_var} \"\${CMAKE_CURRENT_LIST_FILE}\" PATH)") 43 # Construct the proper number of get_filename_component(... PATH) 44 # calls to compute the installation prefix. 45 string(REGEX REPLACE "/" ";" _count "${path_to_leave}") 46 foreach(p ${_count}) 47 list(APPEND config_code 48 "get_filename_component(${prefix_var} \"\${${prefix_var}}\" PATH)") 49 endforeach(p) 50 endif() 51 string(REPLACE ";" "\n" config_code "${config_code}") 52 set("${out_var}" "${config_code}" PARENT_SCOPE) 53endfunction() 54