pkg-config file

[amirouche]

NNG & Platform details.

GNU Linux

Expected Behavior

The build system install a pkg-config .pc file somewhere

Actual Behavior

No .pc is installed

Steps to Reproduce

  $ mkdir build
  $ cd build
  $ cmake -G Ninja ..
  $ ninja
  $ ninja test
  $ ninja install

[gdamore]

I switched to CMake a while ago. I haven't had a chance to reinvestigate pkg-config, which needs to be populated with the specifics of where the package is installed.

[xfbs]

A pkg-config file would be pretty useful for me too. Do you want me to pop one in and send you a pull request?

[xueruini]

We created a pc file internally for easy development.

[gdamore]

Its funny that grousing around I couldn't find any standard way to set this up from cmake. How disappointing.

It's not sufficient to just record the location of the nng library and header tree -- you also need to record dependencies if the installation was static.

Of course, if you're using a static library, you probably should just download the library yourself in your own project tree, rather than relying upon a system installation -- I'm assuming that a system installation is more useful with shared libraries.

[tlsa]

I was going to request this, but found this existing issue already here. Can anything be done about it?

I just found this:
https://discourse.cmake.org/t/how-to-generate-pc-pkg-config-file-supporting-prefix-of-the-cmake-install/4109/9

[gdamore]

I found this :

# this template is filled-in by CMake `configure_file(... @ONLY)`
# the `@....@` are filled in by CMake configure_file(), 
# from variables set in your CMakeLists.txt or by CMake itself
#
# Good tutoral for understanding .pc files: 
# https://people.freedesktop.org/~dbn/pkg-config-guide.html

prefix="@CMAKE_INSTALL_PREFIX@"
exec_prefix="${prefix}"
libdir="${prefix}/lib"
includedir="${prefix}/include"

Name: @PROJECT_NAME@
Description: @CMAKE_PROJECT_DESCRIPTION@
URL: @CMAKE_PROJECT_HOMEPAGE_URL@
Version: @PROJECT_VERSION@
Requires: @pc_req_public@
Requires.private: @pc_req_private@
Cflags: -I"${includedir}"
Libs: -L"${libdir}" -l@target1@ -l@target2@
Libs.private: -L"${libdir}" -l@target1@ -l@target2@ @pc_libs_private@

Some thinking that the libdir needs tweaking as well:

libdir=${exec_prefix}/@CMAKE_INSTALL_LIBDIR@

Anyway there might be hope here.

[gdamore]

Well, after a couple of hours, I've discovered that cmake doesn't have good support for this at all. Essentially we cannot automatically generate the transitive dependencies using "modern" cmake, because it doesn't understand how to expand targets like Thread::threads or whatever, when doing configure_file().

With a variety of optional dependencies, its sufficiently problematic that I don't want to do it.

Meson does have a pkg-config generator.

I'm leaning more and more towards meson.

[gdamore]

I'm going to leave this open for now, but with a help-wanted label. If someone has some brilliant solution to this problem, I'd love to hear it.

The reality is that pkg-config is not very portable and has a bunch of problems. Cmake also has problems, but it has fewer of them then pkg-config.