[cmake-developers] [PATCH] ExternalProject_Add: Allow generator expressions in CMAKE_CACHE_ARGS

[Andrey Pokrovskiy]

> does the external project's configure step re-run when you edit only the CMAKE_CACHE_ARGS for it?

Yes. Verified with the following example:

----
cmake_minimum_required(VERSION 3.2)

project(CMakeExternalProjectGenExpr)

include(ExternalProject)

set(ZF_QUEUE_INSTALL_PREFIX "${CMAKE_CURRENT_BINARY_DIR}/zf_queue.install")

ExternalProject_Add(zf_queue_ep
    GIT_REPOSITORY https://github.com/wonder-mice/zf_queue.git
    UPDATE_COMMAND ""
    INSTALL_DIR ${ZF_QUEUE_INSTALL_PREFIX}
    CMAKE_CACHE_ARGS
        -DCMAKE_INSTALL_PREFIX:string=<INSTALL_DIR>)

On Fri, Apr 17, 2015 at 4:19 AM, David Cole <DLRdave at aol.com> wrote:
> With this change, does the external project's configure step re-run
> when you edit only the CMAKE_CACHE_ARGS for it?
>
> (It did with the *.in / configure_file approach...)
>
>
> On Fri, Apr 17, 2015 at 12:55 AM, Andrey Pokrovskiy
> <wonder.mice at gmail.com> wrote:
>> In current implementation of ExternalProject_Add generator expressions
>> are supported in CMAKE_ARGS (probably by coincidence), but not in
>> CMAKE_CACHE_ARGS. This patch will enable generators expressions in
>> CMAKE_CACHE_ARGS.
>>
>> Use case:
>> set(LIBEV_LIBRARIES $<TARGET_FILE:ev>)
>> ExternalProject_Add(
>>     ...
>>     CMAKE_CACHE_ARGS
>>          -DLIBEV_LIBRARIES=${LIBEV_LIBRARIES}
>>     ...)
>>
>> ---
>>  Modules/ExternalProject.cmake | 5 +----
>>  1 file changed, 1 insertion(+), 4 deletions(-)
>>
>> diff --git a/Modules/ExternalProject.cmake b/Modules/ExternalProject.cmake
>> index 0c73d41..1c7cf51 100644
>> --- a/Modules/ExternalProject.cmake
>> +++ b/Modules/ExternalProject.cmake
>> @@ -1126,10 +1126,7 @@ function(_ep_write_initial_cache target_name
>> script_filename script_initial_cach
>>    # Replace location tags.
>>    _ep_replace_location_tags(${target_name} script_initial_cache)
>>    # Write out the initial cache file to the location specified.
>> -  if(NOT EXISTS "${script_filename}.in")
>> -    file(WRITE "${script_filename}.in" "\@script_initial_cache\@\n")
>> -  endif()
>> -  configure_file("${script_filename}.in" "${script_filename}")
>> +  file(GENERATE OUTPUT "${script_filename}" CONTENT "${script_initial_cache}")
>>  endfunction()
>>
>>
>> --
>> 2.3.2 (Apple Git-55)
>>
>> --
>>
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