Re: cmake support

[Andrew Pennebaker]

Hmm, cmake clearly supports building *libraries and executables* for non-cmake external projects. But in the case of gnulib, gnulib itself does not emit a library or executable, right? It's meant to be sourced inside of another autotools project. Can cmake really be integrated around gnulib, or am I forced to rewrite my project's build system in terms of autotools?

Specifically, could someone clarify how gl_EARLY is supposed to be triggerd by cmake in the inner gnulib project, so that files like openat.h can be sourced from the cmake outer project? I don't know enough about autoconf yet to understand how cmake would do this. It's hard enough getting this far:

# CMakeLists.txt

# Doesn't even work on my machine^TM

add_executable(fewer lib/main.c lib/fewer.c)

if(CMAKE_SYSTEM_NAME MATCHES "Minix")
  ExternalProject_Add(
    gnulib
    SOURCE_DIR "gnulib"
    CONFIGURE_COMMAND "${PROJECT_SOURCE_DIR}/gnulib/gnulib-tool" --dir "${PROJECT_SOURCE_DIR}/gnulib-prefix/src/gnulib-build" --import openat # && autoreconf -i && ./configure
    BUILD_COMMAND echo
    INSTALL_COMMAND echo
  )
  add_dependencies(fewer gnulib)
  target_include_directories(fewer PUBLIC gnulib-prefix/src/gnulib-build/lib)
  target_link_libraries(fewer libgnu)
endif()

On Sun, Jan 6, 2019 at 3:37 AM Kamil Dudka <address@hidden> wrote:

On Sunday, January 6, 2019 3:22:01 AM CET Andrew Pennebaker wrote:
> Ach, I've made a career out of not having to know autotools! ./configure &&
> make && [sudo] make install were black boxes as far as I was concerned.
>
> So be it, I'll spend some time reading up this weekend and see how far I
> get. MSVC integration will become more interesting, but I suppose I can
> disable Gnulib for targets that don't actually need it. This is what I get
> for dipping my toes in CloudABI and introducing dprintf(), openat() to my
> projects :P
>
> Would be nice to offer NetBSD-style packages for MINIX and SmartOS, in
> order to make Gnulib easier to install to a standard include path like with
> other development libraries.

I am afraid that there is no OS distribution that would install Gnulib to
a standard include (and library) path and this is most likely not going to
change because gnulib's developers do not want gnulib to be used this way:

https://www.gnu.org/software/gnulib/manual/html_node/Library-vs-Reusable-Code.html#Library-vs-Reusable-Code

Kamil

> On Sat, Jan 5, 2019 at 12:31 PM Kamil Dudka <address@hidden> wrote:
> > On Saturday, January 5, 2019 6:53:06 PM CET Bruno Haible wrote:
> > > Hi,
> > >
> > > Andrew Pennebaker wrote:
> > > > Could we improve how gnulib integrates with downstream projects, to
> >
> > make
> >
> > > > it
> > > > easier to work with different build tools? In particular, would be
> >
> > helpful
> >
> > > > for gnulib to easily work with cmake projects.
> > > >
> > > > In my case, I have an application that needs openat(), and I already
> >
> > have
> >
> > > > a
> > > > complex cmake configuration that would be difficult to rewrite in
> >
> > terms of
> >
> > > > autotools.
> > >
> > > I don't think we will spend time to make gnulib-tool generate cmake
> > > configurations.
> > >
> > >   1. Because the GNU build system is based on Autotools.
> > >   2. Because many people say that cmake is a horror to use. [1][2]
> >
> > That is not an argument.  You can find similar horror stories about
> >
> > autotools:
> >     http://voices.canonical.com/jussi.pakkanen/2011/09/13/autotools/
> > >
> > > But gnulib-tool by design creates a subdirectory, and you can yourself
> > >
> > >   - add a simple configure.ac to that subdirectory, as outlined in the
> > >   
> > >     documentation [3],
> >
> > When I needed it 10 years ago, I was able to get around this limitation by
> > using the --create-testdir option of gnulib-tool.  It created a directory
> > with configure script that (after running make) produced a static library.
> > I am not sure if this approach had any side effects, like turning on debug
> > build, but I was at least not forced to create configure.ac etc.
> >
> > Kamil
> >
> > >   - integrate this subdirectory with cmake through an 'ExternalProject'
> >
> > [4].
> >
> > > If, during this process, you encounter pain points that require (small)
> > > gnulib-tool changes, please come back to us and report them.
> > >
> > > Bruno
> > >
> > > [1]
> >
> > https://www.reddit.com/r/cpp/comments/4flb8z/fighting_through_a_cmake_hell
> > /
> >
> > > [2]
> > > https://www.reddit.com/r/cpp/comments/7yps20/its_time_to_do_cmake_right/
> > > [3]
> > > https://www.gnu.org/software/gnulib/manual/html_node/Initial-import.html
> > > [4]
> >
> > https://stackoverflow.com/questions/5971921/building-a-library-using-autot
> > o
> >
> > > ols-from-cmake

--

Cheers,

Andrew