pkg-config file is broken when CMAKE_INSTALL_{INCLUDE,LIB}DIR is absolute about orcania

[alexshpilkin]

Well, as @jtojnar points out in the first link above, the docs for GNUInstallDirs explicitly say that the value of a CMAKE_INSTALL_*DIR variable “should typically be a path relative to the installation prefix [...]. However, an absolute path is also allowed.” (NixOS makes occasional use of that to make user and development files go into separate trees, and so just always passes absolute paths even if they are in fact located under the prefix.)

I’ll try to help if you’re willing to rely on my nearly-nonexistent understanding of CMake, but probably not before I finish my first round through all Nix packages with this problem (currently on package 62 of 85 😮‍💨 ).

[babelouest]

Hi,

I'm not familiar with absolute paths for CMAKE_INSTALL_{INCLUDE,LIB}DIR variables, as I understand, the CMAKE_INSTALL_PREFIX is supposed to be an absolute path, to be combined with the CMAKE_INSTALL_* variables.

Also, I took a look at your references and made some tests, but I can't find a solution yet, can you provide a pull request to help with that?

[babelouest]

Out of curiosity, what arguments are you using when packaging for NixOS?

[alexshpilkin]

The CMake infrastructure in Nixpkgs is... general, to put it politely, so a full list of configuration flags is unlikely to be helpful. If you want a quick, non-NixOS-dependent reproduction, here’s one (cf NixOS/nixpkgs#172347):

$ cd /tmp
$ mkdir prefix prefix-include prefix-lib
$ git clone https://github.com/babelouest/orcania
[snip]
$ cd orcania
$ mkdir build && cd build
$ cmake -DCMAKE_INSTALL_PREFIX=/tmp/prefix -DCMAKE_INSTALL_INCLUDEDIR=/tmp/prefix-include -DCMAKE_INSTALL_LIBDIR=/tmp/prefix-lib ..
[snip]
$ make && make install
[snip]
$ grep -r '//tmp/prefix' /tmp/prefix-lib
/tmp/prefix-lib/pkgconfig/liborcania.pc:libdir=${exec_prefix}//tmp/prefix-lib
/tmp/prefix-lib/pkgconfig/liborcania.pc:includedir=${prefix}//tmp/prefix-include
$ # oops, this won't work

If, on the other hand, you’re wondering why anyone would do that, well, on NixOS it’s not exactly that, but the name of the game is to have separate trees (with their own bin, lib, etc.) for every package, link them together following (explicitly declared) dependencies and/or set up search paths so that the set of packages the user wants to be active at the moment gets used.

Thus, when a derivation uses separate dev and/or doc outputs (what would on other systems be separate dev or devel and/or doc packages), those too are placed into completely separate trees (user-usable things like binaries and shared libraries into /nix/store/HASH-NAME-VERSION, developer-usable things like include files and static libraries into /nix/store/HASH-NAME-VERSION-dev, documentation into /nix/store/HASH-NAME-VERSION-doc), and the CMake tooling uses the CMAKE_INSTALL_*DIR variables to achieve that. Now, the Nixpkgs derivation for orcania specifically does not currently separate its outputs in this way because it’s not that large (and because nobody cared to make it so), but the tooling passes absolute paths anyway—for simplicity and because a CMake build system is supposed to accept them in any case.

(To be clear, I’m not the Nixpkgs maintainer for orcania, I’m the person trying to fix these CMake-induced bugs throughout the package set. Nixpkgs is rather chaotic so this is not as unusual as “non-maintainer uploads” would be in other places.)

[babelouest]

I have something that would work.

If I add the following lines in the CMakeLists.txt:

if(IS_ABSOLUTE "${CMAKE_INSTALL_INCLUDEDIR}")
  set(PKGCONFIG_TARGET_INCLUDES "${CMAKE_INSTALL_INCLUDEDIR}")
else()
  set(PKGCONFIG_TARGET_INCLUDES "\${prefix}/${CMAKE_INSTALL_INCLUDEDIR}")
endif()

if(IS_ABSOLUTE "${CMAKE_INSTALL_LIBDIR}")
  set(PKGCONFIG_TARGET_LIBDIR "${CMAKE_INSTALL_LIBDIR}")
else()
  set(PKGCONFIG_TARGET_LIBDIR "\${prefix}/${CMAKE_INSTALL_LIBDIR}")
endif()

And set the file liborcania.pc.in like that:

prefix=@CMAKE_INSTALL_PREFIX@
exec_prefix=@CMAKE_INSTALL_PREFIX@
libdir=@PKGCONFIG_TARGET_LIBDIR@
includedir=@PKGCONFIG_TARGET_INCLUDES@

Name: @PROJECT_NAME@
Description: @PROJECT_DESCRIPTION@
URL: @PROJECT_BUGREPORT_PATH@
Version: @LIBRARY_VERSION@
Requires: @PKGCONF_REQ@
Requires.private: @PKGCONF_REQ_PRIVATE@
Libs: -L${libdir} -lorcania @LIB_STATIC@
Cflags: -I${includedir}

Then, the file liborcania.pc content look like that:

$ # run cmake script with absolute paths for CMAKE_INSTALL_{INCLUDE,LIB}DIR
$ cmake -DCMAKE_INSTALL_PREFIX=/tmp/prefix -DCMAKE_INSTALL_INCLUDEDIR=/tmp/prefix-include -DCMAKE_INSTALL_LIBDIR=/tmp/prefix-lib ..
$ cat liborcania.pc
prefix=/tmp/prefix
exec_prefix=/tmp/prefix
libdir=/tmp/prefix-lib
includedir=/tmp/prefix-include

Name: orcania
Description: Potluck with different functions for different purposes that can be shared among programs
URL: https://github.com/babelouest/orcania/issues
Version: 2.2.2
Requires: 
Requires.private: 
Libs: -L${libdir} -lorcania 
Cflags: -I${includedir}

$ # run cmake script with relative paths for CMAKE_INSTALL_{INCLUDE,LIB}DIR
$ cmake ..
$ cat liborcania.pc
prefix=/usr/local
exec_prefix=/usr/local
libdir=${prefix}/lib
includedir=${prefix}/include

Name: orcania
Description: Potluck with different functions for different purposes that can be shared among programs
URL: https://github.com/babelouest/orcania/issues
Version: 2.2.2
Requires: 
Requires.private: 
Libs: -L${libdir} -lorcania 
Cflags: -I${includedir}

[alexshpilkin]

Yes, that should work, thank you :)