[CMake] Handling of generator expressions

[Robert Maynard]

Hi Roberto,

Can you please report this as an issue (
https://gitlab.kitware.com/cmake/cmake ) as this looks like a bug in
the way we are parsing generator expressions in target_link_libraries.
The target_link_libraries fully supports taking a list of linker flags
when it isn't part of a generator expression.

On Sun, Nov 19, 2017 at 1:16 PM, Roberto Di Remigio
<roberto.diremigio at gmail.com> wrote:
> Hello,
> I am trying to compile the following code snippet:
>
> int main(int argc, char ** argv) {
>   int stack_array[100];
>   stack_array[1] = 0;
>   return stack_array[argc + 100]; // BOOM
> }
>
> The followin CMakeLists.txt works fine, but you can notice that
> target_compile_options takes a list, while target_link_libraries takes a
> string. Always using the string will result in a compilation error, because
> the compiler flags are passed quoted to the compiler. Always using the list
> doesn't work either, because the generator expression is evaluated as
> $<1:-fsanitize=address -fno-omit-frame-pointer> and then passed as-is to the
> linker, which doesn't know what to do with it.
> Is this supposed to be like this? If yes, what's the rationale?
> Thanks in advance!
>   Roberto
>
> cmake_minimum_required(VERSION 3.3 FATAL_ERROR)
>
> project(recipe-09 CXX)
>
> set(CMAKE_CXX_STANDARD 11)
> set(CMAKE_CXX_EXTENSIONS OFF)
> set(CMAKE_CXX_STANDARD_REQUIRED ON)
>
> list(APPEND CXX_BASIC_FLAGS "-g3" "-O1")
>
> include(CheckCXXCompilerFlag)
>
> set(ASAN_FLAGS "-fsanitize=address -fno-omit-frame-pointer")
> set(CMAKE_REQUIRED_FLAGS ${ASAN_FLAGS})
> check_cxx_compiler_flag(${ASAN_FLAGS} asan_works)
> unset(CMAKE_REQUIRED_FLAGS)
>
> add_executable(asan-example asan-example.cpp)
> string(REPLACE " " ";" _asan_flags ${ASAN_FLAGS})
> target_compile_options(asan-example
>   PUBLIC
>     ${CXX_BASIC_FLAGS}
>     $<$<BOOL:${asan_works}>:${_asan_flags}>
>   )
> target_link_libraries(asan-example
>   PUBLIC
>     $<$<BOOL:${asan_works}>:${ASAN_FLAGS}>
>   )
>
> --
>
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