[CMake] Per Target CMAKE_C??_FLAGS Reset/Redefinition

[David Hauck]

Hi Decker,

On Tuesday, May 26, 2015 11:22 AM, CMake wrote:
> SET_TARGET_PROPERTIES( <target> PROPERTIES
>                   COMPILE_FLAGS  "${ExtraFlags}"
>                   COMPILE_DEFINITIONS
> "SIMPLE_FLAG;DEFINED_SYMBOL=xxxx;DEFINED_STRING=\"string value\""
>  )

I'm not sure if this was meant as a solution, but I doubt the above works; these simply *add* to the compile flags, they don't allow for completely replacing/resetting them...

Thanks,
-David

> On Tue, May 26, 2015 at 11:07 AM, Murali Paluru <mpaluru at gmail.com>
> wrote:
> 
> 
> 	Hi David,
> 
> 	The project that I am working on has similar needs of having 
> different flags for each target. I have placed the different targets 
> in different sub- folders and set the CMAKE_*_FLAGS. This approach 
> seems to work fine as you mentioned.
> 
> 	From my understanding, a new add_subdirectory creates a new scope of 
> variables.
> 
> 	I feel that having different targets in different directories is a 
> good logical separation. So if that's working for you, why not use it?
> I am not sure if there is a better way, but I hope someone will comment.
> 
> 	Regards,
> 	Murali.
> 
> 	On Mon, May 25, 2015 at 1:04 PM, David Hauck <davidh at netacquire.com>
> wrote:
> 
> 
> 		Hi,
> 
> 		I've been searching for a definitive discussion of this but haven't 
> been successful finding it. I have a (Unix Makefile) CMakeLists.txt 
> project sub-directory that defines several (3) targets (for executable 
> and shared targets). I'm trying to reset/redefine the CMAKE_C??_FLAGS 
> (specifically CMAKE_C_FLAGS) property on one of the targets via the 
> following statement in the CMakeLists.txt file:
> 
> 		set_property(TARGET <target_name> PROPERTY CMAKE_C_FLAGS "-Wall
> -shared") 		set_property(TARGET <target_name> PROPERTY
> CMAKE_C_FLAGS_DEBUG "-g") 		set_property(TARGET <target_name> PROPERTY
> CMAKE_C_FLAGS_RELEASE "-O3")
> 
> 		However, this isn't working and the resulting target compilation is 
> using the directory's value for these properties. Other redefinitions 
> of per-target properties (e.g., INCLUDE_DIRECTORIES) do seem to take 
> so I'm wondering if certain properties are per-directory only and 
> aren't meaningful with the "set_property(TARGET ...)"
> construct?
> 
> 		If I move the target to its own sub-directory and use the following 
> CMakeLists.txt commands instead the compile flags are properly (re)set:
> 
> 		SET (CMAKE_C_FLAGS "-Wall -shared")
> 		SET (CMAKE_C_FLAGS_DEBUG "-g")
> 		SET (CMAKE_C_FLAGS_RELEASE "-O3")
> 
> 		Oddly the aforementioned "set_property(TARGET..."
> constructs in place of the above "SET(CMAKE..." constructs also fail 
> to reset the flags in this new directory so this doesn't seem related 
> to the sub- directory CMakeLists.txt file when multiple targets are defined.
> 
> 		I must have missed something obvious related to this in the 
> documentation and/or the mailing list/Google. Any ideas?
> 
> 		Thanks,
> 		-David
> 
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