[build2] Building objective C code

[Boris Kolpackov]

Fabian Meyer via users <users at build2.org> writes:

> I am currently trying to compile some objective-C source files using build2
> for MacOS builds of SFML (see https://github.com/build2-packaging/sfml/blob/master/sfml-window/src/buildfile#L72).
> I basically copied the adhoc-recipe from the GLFW package (see
> https://github.com/build2-packaging/glfw/blob/master/glfw/src/buildfile#L24)
> 
> It seems to work or at least do something meaningful. However, during the
> build the compilation of some objective-c files fails, because the compiler
> cannot find certain header files ([...]). The missing header files lie in
> the sfml-system package, which is imported at the top of the buildfile [...].
> Building C++ sources, which also need these headers, works.
> It seems like the exported include paths of the sfml-system dependency are
> not propagated to the adhoc recipe. I tried adding the intf_libs explicitly
> to the adhoc recipe but that did not help.

The current state of the art in Objective-C/C++ compilation is libQt6Core
(warning: it's quite a complex buildfile, and it requires not-yet-released
build2 0.15.0):

https://github.com/build2-packaging/Qt6/blob/master/libQt6Core/QtCore/buildfile

In particular, it solves the problem of obtaining header search paths
from imported libraries (via libul{Qt6CoreMeta}). The buildfile is
quite well commented (IMO), so I think you should be able to figure
out what's going on. But let me know if you have any questions about
any of this.