[cmake-developers] target_include_directories is broken with ninja generator

[Matthew Woehlke]

On 2013-03-13 20:59, Matthew Woehlke wrote:
> This simple CMakeLists.txt is broken with ninja:
>
> cmake_minimum_required(VERSION 2.8.10.20130312)
> project(Foo)
>
> add_executable(foo foo.cpp)
>
> target_include_directories(foo PUBLIC
>    $<BUILD_INTERFACE:${Foo_BINARY_DIR}>
>    $<INSTALL_INTERFACE:${CMAKE_INSTALL_PREFIX}/include>
> )
>
> ...with Ninja, the include directive passed to the compiler is '-I.'
> (with the binary dir prefix similarly stripped for anything after the ${}).
>
> It seems okay with the Makefile generator.
>
> This does appear to be a CMake problem, and not a ninja problem, as in
> the build.ninja I am seeing 'FLAGS = -I.'.
>
> It would be nice to have this fixed before 2.8.11 final :-).
>
> (Note: I haven't yet checked if the installed exports file is okay,
> since this is preventing my project from building, although presumably
> that is at least not generator dependent.)

...and it occurred to me that this might be happening because of a 
misguided optimization to strip unnecessary prefixing of the expected 
working directory from include paths.

First off, it's broken, because I'm being bit by this where the 
directory I want to include is NOT the current binary directory 
(Foo_BINARY_DIR is in fact a parent of CMAKE_CURRENT_BINARY_DIR). 
Second, performing such an optimization is inherently broken (although 
depends where the optimization is happening) for public include_directories.

It may be that someone made an 'oops' when writing the generator code 
and wrote a CMAKE_BINARY_DIR (or equivalent) where 
CMAKE_CURRENT_BINARY_DIR was intended/needed.

-- 
Matthew