[CMake] Interface Libraries allow include directories but not link directories.. Why?

Wed Aug 23 17:57:13 EDT 2017

> Does that work for your needs?

Sadly, no (but thanks!). While this is enough for the arguably common use
case of include directories, compile flags, etc... there are plenty of
things that won't work with this approach.

e.g. none of this works for instance:

project(foo)

add_library(blah INTERFACE)
set_property(TARGET blah PROPERTY SUFFIX ".mxe")
set_property(TARGET blah PROPERTY CXX_STANDARD 14)
set_property(TARGET blah PROPERTY INSTALL_RPATH "@loader_path/whatever")

-------
Jean-Michaël Celerier
http://www.jcelerier.name

On Wed, Aug 23, 2017 at 11:23 PM, Brian Davis <bitminer at gmail.com> wrote:

> So there is some odd replies in the cmake mailing list possibly responses to wrong message, but this looked like a response to mine even if the initial reply to bit is not right from Nicholas.  Anywho here goes:
>
> @Jean-Michaël Celerier
>
> -- snip --
> >* - Says that custom functions such as add_{project}_library shouldn't be
> *used and function definitions should be used as little as possible. Except
> this just leads to extremely verbose CMakeLists where repeated properties
> are defined again and again and again.
> -- snip --
>
> Yes add_project_library were my own and in the process of being deprecated.  These were geared directly at two problems in cmake.
>
> 1) They were used to get CMake to support the concept of "inherited build properties".
>
> 2) As you stated and is still a problem the verbosity of CMake.  Where IMO much could be collaped into one call
>
>
> -- snip --
> I also never understood how to handle this.
> -- snip --
>
> I am afraid I don't ultimately have the answer either... I have do some ideas on possibly best course of action.
>
>
> -- snip --
>  I have a project where I want to define, say, -fsanitize=address, -DFOO_BAR
> and the SUFFIX property on a specific set of 25 targets amongst ~100
> targets. What am I to do ?
>
> * set(CMAKE_CXX_FLAGS "-fsanitize=address") is "not modern CMake" (and also
> would be harder to set / unset on specific targets).
> * calling target_compile_options(...) 25 times ... well I mean, everyone
> knows it's bad to duplicate code. Especially if the change is meant to be
> only when a specific option() is enabled, or for debugging purposes
> * creating a function that would set the correct flags, etc and then call
> this function for each target is apparently "not modern CMake" either.
> * creating and linking to "dummy" INTERFACE targets with the flags and
> properties I want have an awful lot of limitations
>
> So what is the right course of actions here ?
> -- snip --
>
> I have started using add_library( targ INTERFACE ) to imperilment inherited build properties.   Yes the naming convention and use/reuse/misuse of add_library is horrid (library)
>
> I just posted this which may help:
>
> https://cmake.org/pipermail/cmake/2017-August/066119.html
>
> -- snip --
> Ideally I'd like to add "groups" to targets; e.g. "target Foo is a plugin
> for $software", "target Bar is an integration test" and set per-group
> options, flags, properties, etc. Like
>
>     add_group(PluginGroup)
>     target_compile_definitions(PluginGroup -DBLAH)
>     set_property(GROUP PluginGroup PROPERTIES /* whatever in
> cmake-properties*/)
>     set_group(myTarget PluginGroup) // applies everything to the target
> -- snip --
>
> I won't have all the syntax for what your trying but possibly try:
>
> add_library( PluginGroupInterface INTERFACE)
> target_compile_definitions(PluginGroupInterface -DBLAH)
> set_property(GROUP PluginGroup PROPERTIES /* whatever in
> cmake-properties*/)
>
> I add interface, Interface, or _interface to my interface targets I use like this.  Note here library in add library does not actually have to have a library (hence my statements to the horrid miss reuse of add_library for this functionality).  It can just have build properties that you want a target to later inherit as far as I understand it or as far as I am miss using it if it is meant to be used some other way.
>
> then...
>
> add_executable( myTarget )
>
> target_link_libraries(
>   myTarget
>   PluginGroupInterface
> )
>
> Does that work for your needs?
>
>
>
> -- snip --
> Best,
>
> -------
> Jean-Michaël Celerier
>
> -- snip --
>
>
> --
>
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