Modules installed in CMAKE_ROOT

[Michał Sawicz]

Every time cmake is upgraded, we need to rebuild cmake-extras to put the modules in the correct place, even though it's just about the paths.

I believe the installation in CMAKE_ROOT is wrong (only cmake-data installs there), we should instead install in /usr/lib/cmake/ (or /usr/lib/<arch>/cmake/ when files are arch-dependent).

Otherwise, we'd need versioned dependencies to prevent broken cmake + cmake-extras installations.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: cmake-extras 0.6+16.04.20160215-0ubuntu2
ProcVersionSignature: Ubuntu 4.4.0-15.31-generic 4.4.6
Uname: Linux 4.4.0-15-generic x86_64
ApportVersion: 2.20-0ubuntu3
Architecture: amd64
CurrentDesktop: Unity
Date: Tue Mar 29 23:42:12 2016
Dependencies:

PackageArchitecture: all
SourcePackage: cmake-extras
UpgradeStatus: No upgrade log present (probably fresh install)

[Michi Henning (michihenning)]

We can install in /usr/lib/cmake/cmake-extras, but that is not backward compatible.

cmake looks in CMAKE_MODULE_PATH for additional modules but, by default, CMAKE_MODULE_PATH is empty, so the extra modules are not found. The only place cmake looks at by default appears to be ${CMAKE_ROOT}/Modules, unfortunately.

We can make this change, but all projects using cmake-extras will have to set CMAKE_MODULE_PATH explicitly:

set(CMAKE_MODULE_PATH /usr/lib/cmake/cmake-extras)

[Michał Sawicz (saviq)]

I just looked at other projects that install cmake bits, and the two locations common between them are those:

$ dpkg -S /usr/lib/cmake
libjsoncpp-dev:amd64: /usr/lib/cmake

$ dpkg -S /usr/lib/x86_64-linux-gnu/cmake/Qt5
qtbase5-dev:amd64: /usr/lib/x86_64-linux-gnu/cmake/Qt5

While nothing else than cmake itself and cmake-extras installs in the versioned directory:

$ dpkg -S /usr/share/cmake-3.5
cmake-data, cmake-extras: /usr/share/cmake-3.5

By "not backwards compatible", what do you mean? I don't think we need to be compatible further back than... our current cmake TBH.