[CMake] Include-Dir order problem

[David Cole]

On Wed, Feb 16, 2011 at 2:32 AM, Andreas Pakulat <apaku at gmx.de> wrote:
On 16.02.11 03:48:03, Michael Hertling wrote:
>
> > On 02/15/2011 07:36 PM, Andreas Pakulat wrote:
> > > On 15.02.11 17:54:29, Michael Hertling wrote:
> > >> On 02/13/2011 01:27 AM, Andreas Pakulat wrote:
> > >>> Hi,
> > >>>
> > >>> I've got a somewhat tricky problem here with include directories. I'm
> > >>> building a couple of source files and for some of them I need to add
> an
> > >>> include-directory to the front of the list that cmake passes to the
> > >>> compiler. At the same time other source files in that directory need
> to
> > >>> not have that include-dir in front of the list.
> > >>>
> > >>> I can't see a way to do this, except by using COMPILE_FLAGS source
> file
> > >>> properties for each and every file to specify include-dirs and not
> use
> > >>> include_directories at all, as COMPILE_FLAGS always end up behind the
> > >>> includes.
> > >>>
> > >>> So, am I missing something here? If not I guess I'll have to find
> that
> > >>> bugreport about making include-dirs a source-file property and vote
> for
> > >>> it so it gets included into 2.8.5...
> > >>
> > >> Currently, AFAIK, it's not possible to set source-file-specific
> include
> > >> directories unless one (mis)uses COMPILE_FLAGS which is accompanied by
> > >> the shortcoming you've mentioned. Probably, the really clean solution
> > >> ATM would be a reorganisation of the sources, but I doubt if the need
> > >> for different include directories is an appropriate criterion for a
> > >> project's directory layout.
> > >
> > > Well, all those sources need to be in the same target, so I can't quite
> > > see how moving some of the sources into subdirs wuld help with that.
> >
> > Look at the following CMakeLists.txt files:
> >
> > # CMakeLists.txt:
> > CMAKE_MINIMUM_REQUIRED(VERSION 2.8 FATAL_ERROR)
> > PROJECT(INCLUDEDIRECTORIES C)
> > ADD_SUBDIRECTORY(subdir)
> > INCLUDE_DIRECTORIES(abc)
> > FILE(WRITE ${CMAKE_BINARY_DIR}/main.c "int main(void){f();return 0;}\n")
> > ADD_EXECUTABLE(main main.c)
> > TARGET_LINK_LIBRARIES(main sub)
> >
> > # subdir/CMakeLists.txt:
> > INCLUDE_DIRECTORIES(xyz)
> > FILE(WRITE ${CMAKE_CURRENT_BINARY_DIR}/f.c "void f(void){}\n")
> > ADD_LIBRARY(sub STATIC f.c)
> >
> > So, main.c and f.c are compiled with different include directories, but
> > the "main" target is effectively composed from the same object files as
> > if f.c had been explicitly mentioned among the source files for "main".
> > If you commute the ADD_SUBDIRECTORY() and INCLUDE_DIRECTORIES() commands
> > in the top-level CMakeLists.txt, the include directories for main.c will
> > also hold for f.c while the latter still has its own - additional - ones.
> >
> > Things become worse if the target to be built is a shared library.
>
> Exactly my case.
>
> > Most probably, you don't want an additional libsub.so, so you would
> > need to compile f.c at least with "-fPIC" as COMPILE_FLAGS to get
> > further along with a static library. Alternatively, you might use a
> > RULE_LAUNCH_LINK property in order to capture the object files from
> > the subdirectory and incorporate them in the actual target, see [1].
> > However, then you would be restricted to a Makefile generator. IMO,
> > none of these appoaches is really convincing why one should aim at an
> > INCLUDE_DIRECTORIES source file and target property.
>
> Unfortunately it seems Brad is unwilling to implement this unless it can
> be done 'properly' for all generators. Which is sad, but for now I could
> solve this with local special header files which are used by those cpp
> files that would otherwise need the extra directory in front.
>


In my opinion, this is not sad, but commendable. I *hate* the features of
CMake that only work with generator a, b and c, but not the rest of them.
Features of CMake that only work under *some* circumstances are frustrating
to deal with at best.



>
> Andreas
>
> --
> Your object is to save the world, while still leading a pleasant life.
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