[cmake-developers] Adding logic to CMake for -fPIE and -fPIC

[Stephen Kelly]

Brad King wrote:

> On 05/25/2012 04:47 PM, Stephen Kelly wrote:
>> I'm also not completely certain about the change to the try_compile
>> behavior in the branch. Could there be any reason to use
>> set(CMAKE_POSITION_INDEPENDENT_CODE ON) but want to do a try_compile
>> without -fPI{C,E} ? My guess is no, because one would do the try_compile
>> before conditionally setting that property, I guess.
> 
> Since project's don't currently set CMAKE_POSITION_INDEPENDENT_CODE
> there is no compatibility problem.  I think it is okay to honor that
> for try_compile.  It is more representative of how the sources will
> actually be compiled in the calling project.
> 
> The current topic looks pretty good so far.  There is some more work
> to be done.  Please see the block at the bottom of this message for
> the documentation I recommend using for CMP0018.

Done, in a new force push.

> 
> Look at the logic in cmLocalGenerator::AppendFeatureOptions for
> handling of _COMPILE_OPTIONS_ values.  We need to use
> ExpandListArgument to ensure that options are separated as
> CMake-style lists instead of whitespace.  That is the convention
> I'm establishing for "COMPILE_OPTIONS" platform variables.  It will
> not make a difference for single-argument options like "-fPIC" but
> could if some platforms have multi-argument options.
> 
> Before merging we will need to add the equivalent to the hunk
> 
> +  set(CMAKE_${lang}_COMPILE_OPTIONS_PIC "-fPIC")
> +  set(CMAKE_${lang}_COMPILE_OPTIONS_PIE "-fPIE")
> 
> on all necessary platforms.  The policy can't be per-platform.
> You already have a TODO comment for this.

Done, though I left some notes in the commit for now. It seems the existing 
variable is used for more than just PIC equivalents.

Thanks,

Steve.