[CMake] SET_TARGET_PROPERTIES funny..

[Brad King]

Thomas Hunger wrote:
> Hi,
> When I do this to SET_TARGET_PROPERTIES:
> 
> SET_TARGET_PROPERTIES(extree PROPERTIES 
>                       COMPILE_FLAGS "\n")
> 
> make (not cmake) will complain:
> 
> CMakeFiles/XXX/build.make:61: *** missing separator.  Stop.
> 
> This is not out of thin air. I made a different PKGCONFIG macro which 
> fits my needs better:
> 
> FIND_PROGRAM(PKGCONFIG_EXECUTABLE NAMES pkg-config 
> PATHS /usr/local/bin )
> 
> MACRO(PKGCONFIG _target _package)
>     EXEC_PROGRAM(${PKGCONFIG_EXECUTABLE} 
>                  ARGS ${_package} --libs 
>                  OUTPUT_VARIABLE _libs)
>     EXEC_PROGRAM(${PKGCONFIG_EXECUTABLE} 
>                  ARGS ${_package} --cflags 
>                  OUTPUT_VARIABLE _cflags)
>     SET_TARGET_PROPERTIES(${_target} PROPERTIES 
>                           LINK_FLAGS ${_libs} 
>                           COMPILE_FLAGS ${_cflags})
> ENDMACRO(PKGCONFIG)
> 
> Now sqlite3 provides a sqlite3.pc file with an cflags field of "\n". 
> Which is used by SET_TARGET_PROPERTIES. I could catch that error in 
> my macro, but I think it would be better to catch it in 
> SET_TARGET_PROPERTIES. What do you think?

The COMPILE_FLAGS property is meant for passing low-level
platform-specific flags to the compiler.  This is why it uses the
general-purpose property interface.  SET_TARGET_PROPERTIES should not
try to interpret the value of any property.

Extracting information from pkg-config is just another way of doing a
library find operation.  Commands like EXEC_PROGRAM are meant for such
low-level operations.  You can use the STRING command to fix values
before passing them to COMPILE_FLAGS.

-Brad