Re: cmake support

[Andrew Pennebaker <andrew.pennebaker@gmail.com>]

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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 <kdudka@redhat.com> 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 <kdudka@redhat.com> 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

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