Using cmake (version 3.23.0) the build fails to link the utils
```
[...]
[ 87%] Linking C executable bin/visualinfo [113/5249]
/usr/x86_64-pc-linux-gnu/bin/cmake -E cmake_link_script CMakeFiles/visualinfo.dir/link.txt --verbose=1
/usr/host/bin/x86_64-pc-linux-gnu-cc -Wall -g -ggdb3 -O0 -rdynamic CMakeFiles/visualinfo.dir/home/marv/scm/github/glew/src/visualinfo.c.o -o bin/visualinfo -Wl,-rpath,/h
ome/marv/scm/github/glew/build-obj/lib: lib/libGLEW.so.2.2.0 -lSM -lICE -lX11 -lXext -lOpenGL -lSM -lICE -lX11 -lXext
/usr/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-ld: CMakeFiles/visualinfo.dir/home/marv/scm/github/glew/src/visualinfo.c.o: in function `main':
/home/marv/scm/github/glew/src/visualinfo.c:198: undefined reference to `glXQueryExtensionsString'
/usr/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-ld: CMakeFiles/visualinfo.dir/home/marv/scm/github/glew/src/visualinfo.c.o: in function `CreateContext':
/home/marv/scm/github/glew/src/visualinfo.c:1204: undefined reference to `glXQueryExtension'
/usr/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-ld: /home/marv/scm/github/glew/src/visualinfo.c:1206: undefined reference to `glXChooseVisual'
/usr/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-ld: /home/marv/scm/github/glew/src/visualinfo.c:1209: undefined reference to `glXCreateContext'
/usr/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-ld: /home/marv/scm/github/glew/src/visualinfo.c:1221: undefined reference to `glXMakeCurrent'
/usr/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-ld: CMakeFiles/visualinfo.dir/home/marv/scm/github/glew/src/visualinfo.c.o: in function `DestroyContext':
/home/marv/scm/github/glew/src/visualinfo.c:1227: undefined reference to `glXDestroyContext'
/usr/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-ld: lib/libGLEW.so.2.2.0: undefined reference to `glXGetProcAddressARB'
/usr/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-ld: lib/libGLEW.so.2.2.0: undefined reference to `glXQueryVersion'
/usr/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-ld: lib/libGLEW.so.2.2.0: undefined reference to `glXGetClientString'
collect2: error: ld returned 1 exit status
```
Commit 2b50f4a ("CMake: Prefer GLVND if available") changed the cmake
policy CMP0072 to `NEW` in order to make the FindOpenGL module prefer the
GLVND libraries (libOpenGL and libGLX) over the legacy GL library (libGL).
The help of the CMP0072 policy states:
> CMP0072
> -------
>
> .. versionadded:: 3.11
>
> ``FindOpenGL`` prefers GLVND by default when available.
>
> The ``FindOpenGL`` module provides an ``OpenGL::GL`` target and an
> ``OPENGL_LIBRARIES`` variable for projects to use for legacy GL interfaces.
> When both a legacy GL library (e.g. ``libGL.so``) and GLVND libraries
> for OpenGL and GLX (e.g. ``libOpenGL.so`` and ``libGLX.so``) are available,
> the module must choose between them. It documents an ``OpenGL_GL_PREFERENCE``
> variable that can be used to specify an explicit preference. When no such
> preference is set, the module must choose a default preference.
>
> CMake 3.11 and above prefer to choose GLVND libraries. This policy provides
> compatibility with projects that expect the legacy GL library to be used.
>
> The ``OLD`` behavior for this policy is to set ``OpenGL_GL_PREFERENCE`` to
> ``LEGACY``. The ``NEW`` behavior for this policy is to set
> ``OpenGL_GL_PREFERENCE`` to ``GLVND``.
>
> This policy was introduced in CMake version 3.11. CMake version
> 3.23.0 warns when the policy is not set and uses ``OLD`` behavior.
> Use the ``cmake_policy()`` command to set it to ``OLD`` or ``NEW``
> explicitly.
>
> .. note::
> The ``OLD`` behavior of a policy is
> ``deprecated by definition``
> and may be removed in a future version of CMake.
The changes from the mentioned commit combined with the new behaviour of
the FindOpenGL module resulted in the glew library being linked against
`libOpenGL` instead of `libGL`, but not `libGLX`. Since `libOpenGL`
doesn't link against GLX compared to `libGL` the linker errors above
surfaced. Fix this by explicitly linking against libGLX if GLEW_X11 is
enabled
With this commit, when building or installing `glew`, VERSION and
SOVERSION symlinks to the `glew` shared library are created in the
library installation folder if the platform supports them and the linker
supports so-names.
VERSION and SOVERSION specify, respectively, the build version and API
version of the shared library.
As an example, under macOS, the following symlinks will be created:
libGLEW.2.0.0.dylib (the shared library)
libGLEW.2.0.dylib -> libGLEW.2.0.0.dylib (VERSION symlink)
libGLEW.dylib -> libGLEW.2.0.dylib (SOVERSION symlink)
Fixes#141
CMake 2.8.5 added the GNUInstallDirs module, which provides various
variables following the CMAKE_INSTALL_*DIR pattern to allow users a more
flexible installation setup and to provide sensible defaults while
respecting distribution specific install locations like lib64 for RPM
based linux distributions or debian multiarch tuples.
any issues with mixing compilers and library versions. The Visual Studio
Projects need some touching up to get all of the settings synced up for all
of the build variants.
Installs a config module if CMake verion >= 2.8.12.
The config-module creates the import library targets
built in the project (glew, glew_s, glewmx, glewmx_s)
but in accordance with the FindGLEW module shipped with
CMake, it also creates GLEW::GLEW and GLEW::GLEWMX.
GLEW::GLEW and GLEW::GLEWMX will be simply copies of
glew/glewmx or glew_s/glewmx_s. If both versions are
available they alias the shared versions.
The default behaviour can be changed either when installing
or when using the package:
- Set BUILD_SHARED_LIBS to OFF or ON when building and
installing GLEW. This controls which libraries
(shared or static) will be installed (and not which
will be built).
- Set GLEW_USE_STATIC_LIBS to OFF or ON before calling
`find_package(GLEW CONFIG REQUIRED)` to force
the config-module to create GLEW::GLEW and GLEWMX
as aliases to glew/glewmx or glew_s/glewmx_s
The script ./cmake-testbuild.sh is added to test the
CMake build and config-module. See instructions there.
