[CMake] Are header-only targets supported?

[David Cole]

You could use a block like this:

if(CMAKE_GENERATOR STREQUAL "Xcode")
  ...
endif()


HTH,
David


On Mon, Nov 1, 2010 at 8:54 AM, Pedro d'Aquino <budsbd at gmail.com> wrote:
> Hi,
>
> I'd like to add some header-only targets to my build in order to aid
> in project-browsing in IDEs such as Xcode.
>
> If I do "add_library( Common ${header_list} )" the new target shows up
> and compiles fine in Xcode, but when I try to compile it using make, I
> get the following errors:
>
> -------------------------
>
> MacBook-Pro:build_mac pfranco$ cmake ../../myproject
> ...
> -- Configuring done
> CMake Error: Cannot determine link language for target "Common".
> CMake Error: CMake can not determine linker language for target:Common
> ...
> MacBook-Pro:build_mac pfranco$ make Common
> Scanning dependencies of target Common
> make[3]: *** No rule to make target `common/CMakeFiles/Common.dir/build'.  Stop.
> make[2]: *** [common/CMakeFiles/Common.dir/all] Error 2
> make[1]: *** [common/CMakeFiles/Common.dir/rule] Error 2
> make: *** [Common] Error 2
>
> -------------------------
>
> I tried to work around this by adding "set_target_properties( Common
> PROPERTIES LINKER_LANGUAGE CXX)", in which case CMake runs without
> hiccups but make fails (still no problems in Xcode though):
>
> -------------------------
>
> MacBook-Pro:build_mac pfranco$ make Common
> Linking CXX static library libCommon.a
> ar: no archive members specified
> usage:  ar -d [-TLsv] archive file ...
>        ar -m [-TLsv] archive file ...
>        ar -m [-abiTLsv] position archive file ...
>        ar -p [-TLsv] archive [file ...]
>        ar -q [-cTLsv] archive file ...
>        ar -r [-cuTLsv] archive file ...
>        ar -r [-abciuTLsv] position archive file ...
>        ar -t [-TLsv] archive [file ...]
>        ar -x [-ouTLsv] archive [file ...]
> make[3]: *** [common/libCommon.a] Error 1
> make[2]: *** [common/CMakeFiles/Common.dir/all] Error 2
> make[1]: *** [common/CMakeFiles/Common.dir/rule] Error 2
> make: *** [Common] Error 2
>
> -------------------------
>
> Adding a dummy source file works, but causes some ugly warnings I'd
> really like to avoid (besides being a bit hackish):
>
> -------------------------
>
> MacBook-Pro:build_mac pfranco$ make Common
> [100%] Building CXX object common/CMakeFiles/Common.dir/dummy.cpp.o
> Linking CXX static library libCommon.a
> /usr/bin/ranlib: for architecture: i386 file: libCommon.a(dummy.cpp.o)
> has no symbols
> /usr/bin/ranlib: for architecture: x86_64 file:
> libCommon.a(dummy.cpp.o) has no symbols
> /usr/bin/ranlib: warning for library: libCommon.a for architecture:
> i386 the table of contents is empty (no object file members in the
> library define global symbols)
> /usr/bin/ranlib: warning for library: libCommon.a for architecture:
> x86_64 the table of contents is empty (no object file members in the
> library define global symbols)
> [100%] Built target Common
>
> -------------------------
>
> I've looked up a 3 year old e-mail thread
> (http://www.cmake.org/pipermail/cmake/2007-May/014238.html) from which
> I gather this isn't really a supported scenario.
>
> Has anything changed since then? What is the best way of doing this?
>
> Thanks,
>
> Pedro d'Aquino
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