Use gflags ALIAS target instead of ${gflags_XXX} variables

[v1bri]

The gflags project recently added an ALIAS library target for gflags which can be used instead of the legacy ${gflags_INCLUDES} and ${gflags_LIBRARIES} variables. This will also allow removal of the target_include_directories line for gflags. Happy to submit a pull request if this sounds good.

[Mizux]

Sorry for the necro posting but why the gflags ALIAS is not used in DetermineGflagsNamespace.cmake#L37 ?

note: As a workaround when using glog and gflags as subprojects you can use:

add_subdirectory(gflags EXCLUDE_FROM_ALL)
...
# Download and unpack glog at configure time using ExternalProject
...
# Bypass DetermineGflagsNamespace
set(gflags_NAMESPACE "gflags" CACHE INTERNAL "Namespace for gflags")
add_subdirectory(${CMAKE_BINARY_DIR}/glog-src ${CMAKE_BINARY_DIR}/glog-build
	EXCLUDE_FROM_ALL)

[sergiud]

@Mizux Please create a new issue. Thanks!

[Mizux]

Well, according to the try_compile command doc

LINK_LIBRARIES <libs>...
Specify libraries to be linked in the generated project.
The list of libraries may refer to system libraries and to Imported Targets from the calling project.

So in my case where I have gflags and glog as subproject of a meta CMake it didn't work either...

[sergiud]

@Mizux Maybe the $<TARGET_NAME:gflags> generator expression can help here?

[Mizux]

@sergiud I doesn't help
Actually, the CMake source code just ignore target which are not "imported" so having gflags as subdirectory won't work but for a legal find_package(gflags) it should not be a problem IMHO.

EDIT: since try_compile() is done at configure time, you can't rely on target which will be available at buildtime...