[CMake] Recursively include target include directories only

[Petr Kmoch]

On Thu, Jun 18, 2015 at 1:43 AM, Robert Dailey <rcdailey.lists at gmail.com>
wrote:

> On Wed, Jun 17, 2015 at 4:31 PM, Dan Liew <dan at su-root.co.uk> wrote:
> > On 17 June 2015 at 12:28, Robert Dailey <rcdailey.lists at gmail.com>
> wrote:
> >> Is there a way to only take (recursively) the include directiories from
> >> a target or set of targets? I know that include directories propagate
> >> when passing targets to target_link_libraries(), but I do not want to
> >> link the libs; I only want the include directories.
> >>
> >> How can I do this? Thanks.
>

I haven't tested this, but it should be possible to drag in the interface
properties explicitly with generator expressions. Something like this:

add_executable(Depender ...)
target_include_directories(Depender PRIVATE
  $<TARGET_PROPERTY:Dependee1,INTERFACE_INCLUDE_DIRECTORIES>
  $<TARGET_PROPERTY:Dependee2,INTERFACE_INCLUDE_DIRECTORIES>
)

dtto for other INTERFACE_... properties you might need.

Petr


> >
> > I presume recursively you mean propagating the required include
> > directories between targets rather anything to do recursively handling
> > directories.
> >
> > As you mentioned include directories do propagate but this only
> > happens under certain conditions (when using PUBLIC or INTERFACE
> > scopes).
> >
> > I don't know of a way of doing it without target_link_libraries but if
> > it is necessary for you to do this it sounds like you have bigger
> > problems relating to the way you have your project header files
> > organised.
> >
> > The approach I use for include directories is to have all includes for
> > the project rooted in a single include directory in the source tree
> > and have all includes relative to that directory. Then if I you
> >
> > ```
> > include_directories(${CMAKE_SOURCE_DIR}/include)
> > include_directories(${CMAKE_BINARY_DIR}/include) # for generated header
> files
> > ```
> >
> > in the root of the project you never need to set include paths
> > anywhere else for sources that are in your project tree. E.g. if there
> > is header file in
> >
> > ${CMAKE_SOURCE_DIR}/include/project/moduleA/interface.h
> >
> > then in the sources this is included as
> >
> > #include "project/moduleA/interface.h"
> >
> > (note there are never relative header file includes).
> >
> > This is the approach that the LLVM project uses which is very simple
> > and very clean (take a look at the sources). This also works very well
> > for installing your header files, the contents of ${CMAKE_SOURCE_DIR}
> > just need to be copied into /usr/include .
>
> Thanks, I will go through this and see if it helps.
>
> The reason I'm asking this question is because of how I handle unit
> tests in CMake right now. Instead of just defining an executable
> target for the test and then adding a link dependency on the library
> containing the class or set of classes to be tested, I am manually
> pulling in the CPP and H file into the test target and building them
> inline with the test code. This is to support mocking (I can't mock
> objects already compiled into a static library). As such, I need the
> transitive includes and defines, but I do not want the transitive link
> libraries.
>
> If there is a better structure or overall approach I'm happy to
> listen! This has been a nightmare so far.
> --
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