Configuring DIET's compilation: cmake quick introduction

If you are already experienced with cmake then using it to compile DIET should provide no surprise. DIET respects cmake's best practices e.g. by clearly separating the source tree from the binary tree (or compile tree), by exposing the main configuration optional flag variables prefixed with DIET_ (and by hiding away the technical variables) and by not postponing configuration difficulties (in particular the handling of external dependencies like libraries) to compile stage.

Cmake classically provides two ways for setting configuration parameters in order to generate the makefiles in the form of two commands ccmake and cmake (the first one has an extra "c" character):

ccmake [options] <path-to-source>
in order to specify the parameters interactively through a GUI interface

cmake [options] <path-to-source> [-D<var>:<type>=<value>]
in order to define the parameters with the -D flag directly from the command line.

In the above syntax description of both commands, <path-to-source> specifies a path to the top level of the source tree (i.e. the directory where the top level CMakeLists.txt file is to be encountered). Also the current working directory will be used as the root of the build tree for the project (out of source building is generally encouraged especially when working on a CVS tree).

Here is a short list of cmake internal parameters that are worth mentioning:

• CMAKE_BUILD_TYPE controls the type of build mode among which Debug will produce binaries and libraries with the debugging information
• CMAKE_VERBOSE_MAKEFILE is a Boolean parameter which when set to ON will generate makefiles without the .SILENT directive. This is useful for watching the invoked commands and their arguments in case things go wrong.
• CMAKE_C[XX]_FLAGS* is a family of parameters used for the setting and the customization of various C/C++ compiler options.
• CMAKE_INSTALL_PREFIX variable defines the location of the install directory (defaulted to /usr/local on un*x). This is cmake's portable equivalent of the autotools configure's -prefix= option.

Eventually, here is a short list of ccmake interface tips:

• when lost, look at the bottom lines of the interface which always summarizes ccmake's most pertinent options (corresponding keyboard shortcuts) depending on your current context
• hitting the "h" key will direct you ccmake embedded tutorial and a list of keyboard shortcuts (as mentioned in the bottom lines, hit "e" to exit)
• up/down navigation among parameter items can be achieved with the up/down arrows
• when on a parameter item, the line in inverted colors (close above the bottom of the screen) contains a short description of the selected parameter as well as the set of possible/recommended values
• toggling of boolean parameters is made with enter
• press enter to edit path variables
• when editing a PATH typed parameter the TAB keyboard shortcut provides an emacs-like (or bash-like) automatic path completion.
• toggling of advanced mode (press "t") reveals hidden parameters