MS RFC 92: Migrating from Autotools to CMake¶

Date: 2013/03/26
Author: Thomas Bonfort
Contact: thomas.bonfort@gmail.com
Status: Adopted
Version: MapServer 6.4

1. Overview¶

Our current autoconf + Makefile setup has several limitations:

searching for external dependencies is inconsistent between searched libraries
some external dependencies are not found in their default locations, forcing the inclusion of default locations in the compiler/linker flags, and thus preventing the usage of other dependencies installed in non-standard locations (e.g. if -L/usr/lib is added to the linker flags, then /usr/lib/libgdal.so will be used even if the user asked to use gdal from /opt/local/)
the number of iterations that happened in configure.in are starting to show… maintaining this file is now a fairly evolved task
Build files for platforms that do not support autotools are hand maintained alongside the standard Makefiles
Mapscript builds are not streamlined with the principal build, and require custom instructions for each language
Supported features and available system functions are declared as defines on the compiler command line, preventing the safe usage of our headers without the need to know exactly what defines should be added (thus the need for the mapserver-config and mapservervars hacks to be able to build mapscripts)

2. Proposed solution¶

Switch to cmake (http://www.cmake.org) to replace our autoconf + Makefile.in setup. Cmake is aimed at building and installing c/c++ projects in a cross-platform way.

3. Implementation Details¶

remove the current autotools/Makefile related files
implement CMakefiles replicating our search for dependencies and build
use a generated mapserver-config.h included by mapserver.h that contains the defines that we are now passing on the command line (-DUSE_OGR or -DNEED_STRSTR)
store MapServer release information in the CMakefiles, and include that information in a generated mapserver-version.h

3.2 Files affected¶

Files removed:

*/Makefile */Makefile.in
configure.in configure
aclocal.m4
README.Configure

Files added:

*/CMakeLists.txt
mapserver-config.h.in
mapserver-version.h.in

3.3 MapScript¶

Mapscript building will be streamlined with the main build process, and usually requires the presence of SWIG.

3.4 Backwards Compatibility Issues¶

Current ./configure handling will not be supported.
Linking against dependencies available as a static library only is not supported directly. Workarounds should be possible and will be documented if that need arises
Installed binaries will not have their rpath to libmapserver set. If libmapserver is installed to a non-standard location, then LD_LIBRARY_PATH will have to be set pointing to that location.
Current win32 buildfiles would need to be updated as the NEED_STRXXX defines have been renamed in mapserver.h to HAVE_STRXXX

4. Tips when migrating from autotools habits¶

Cmake builds should preferably be run “out-of-source”, i.e. in a separate directory from the source files:
```
$ cd mapserver
$ mkdir build
$ cd build
$ cmake ..
# fix dependency problems
$ make
```
Many new features are enabled/looked for by default instead of being silently ignored.
Missing dependencies are reported with an error message indicating the resolution. An unwanted dependency can be disabled by adding -DWITH_XXX=0 to the cmake invocation (e.g. -DWITH_FRIBIDI=0 -DWITH_WFS=0)
Mapscripts are not built by default and are enabled by adding -DWITH_PHP=1 -DWITH_PYTHON=1, etc…
Dependencies that are installed outside of default locations can be referenced by adding -DCMAKE_PREFIX_PATH=/path/to/gdal-prefix;/path/to/libxml2-prefix

5. Performance implications¶

None

6. Bug ID¶

https://github.com/MapServer/MapServer/issues/4617

7. Voting history¶

+1 from ThomasB, MikeS, TomK, JeffM, DanielM, OlivierC, SteveL, SteveW and PerryN

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