No option for spaces in CMAKE_ARGS

[Thalhammer]

• I've read Brief overview section and do understand basic concepts. Yes
• I've read F.A.Q. section and there is no solution to my problem there. Yes
• I've read Code of Conduct, I promise to be polite and will do my best at being constructive. Yes
• I've read Reporting bugs section carefully. Yes
• I've checked that all the hunter_add_package/find_package API used by me in the example is the same as in documentation. Yes
• I'm using latest Hunter URL/SHA1. Yes

• I've created SSCCE reproducing the issue:

# CMakeLists.txt
cmake_minimum_required(VERSION 3.13)
include("cmake/HunterGate.cmake")
HunterGate(
    URL "https://github.com/cpp-pm/hunter/archive/v0.23.314.tar.gz"
    SHA1 "95c47c92f68edb091b5d6d18924baabe02a6962a"
    LOCAL
)
project(repro)
hunter_add_package(CURL)
find_package(CURL CONFIG REQUIRED)
add_executable(dummy main.cpp)
target_link_libraries(dummy CURL::libcurl)

#./cmake/Hunter/config.cmake
hunter_config(
    CURL
    VERSION 7.74.0-p2
    CMAKE_ARGS CMAKE_C_FLAGS=-ffunction-sections CMAKE_C_FLAGS=-fdata-sections
)

• I'm building on Linux
• I'm using system CMake
• CMake version: 3.18.4

Expected behaviour

Hunter should pass "-ffunction-sections -fdata-sections" as the value of CMAKE_C_FLAGS.

Actual behaviour

Only the last one is passed.

Other

I also tried the following variations:
CMAKE_ARGS CMAKE_C_FLAGS=-ffunction-sections -fdata-sections => Failure parsing arguments.
CMAKE_ARGS CMAKE_C_FLAGS="-ffunction-sections -fdata-sections" => Configures fine but cmake fails to build anything.
CMAKE_ARGS CMAKE_C_FLAGS='-ffunction-sections -fdata-sections' => Same as double quotes.

I think the problem is in how the arguments are passed to the cmake subproject. If I peek into Build/CURL/args.cmake in the build directory I get either

set("CMAKE_C_FLAGS" "-ffunction-sections" CACHE INTERNAL "")
set("CMAKE_C_FLAGS" "-fdata-sections" CACHE INTERNAL "")

with multiple arguments or

set("CMAKE_C_FLAGS" ""-ffunction-sections -fdata-sections"" CACHE INTERNAL "")

with quotes.

The proper result is probably something like this:

set("CMAKE_C_FLAGS" "-ffunction-sections -fdata-sections" CACHE INTERNAL "")

I am not familiar with hunter, but assuming args.cmake is loaded into a more or less clean environment it might be the easiest option to modify the generation code to generate this:

set("CMAKE_C_FLAGS" "${CMAKE_C_FLAGS} -ffunction-sections" CACHE INTERNAL "")
set("CMAKE_C_FLAGS" "${CMAKE_C_FLAGS} -fdata-sections" CACHE INTERNAL "")

If there is a different option or I am missunderstanding something please let me know.

EDIT: CMAKE_ARGS CMAKE_C_FLAGS=-ffunction-sections\ -fdata-sections works, but it feels awfull and is not documented anywhere.

[rbsheth]

CMake's quoting behavior can be annoying at times, but escaping the space here seems like the right thing unfortunately. Perhaps we should add to the documentation somewhere?