[CMake] providing library information, what's the cmake way

[David Cole]

On Wed, Nov 24, 2010 at 11:34 AM, Rolf Eike Beer <eike at sf-mail.de> wrote:
>> On Wed, Nov 24, 2010 at 6:57 AM, Rolf Eike Beer <eike at sf-mail.de> wrote:
>>>> In KDE we have a macro MACRO_WRITE_BASIC_CMAKE_VERSION_FILE() which
>>>> helps
>>>> with
>>>> creating a basic version-info file which should be installed along with
>>>> the
>>>> Config-file.
>>>> It consists of MacroWriteBasicCMakeVersionFile.cmake and
>>>> BasicFindPackageVersion.cmake.in which you can find in
>>>> http://websvn.kde.org/trunk/KDE/kdelibs/cmake/modules/ .
>>>
>>> I wonder why you use
>>>
>>> get_filename_component(_currentListFileDir ${CMAKE_CURRENT_LIST_FILE}
>>> PATH)
>>>
>>> in there instead of CMAKE_CURRENT_LIST_DIR.
>
>> Probably because CMAKE_CURRENT_LIST_DIR was just invented and is only
>> in CMake 2.8.3... get_filename_component works with several versions
>> of CMake, and does not require 2.8.3 or later.
>
> So I think it is _really_ necessary to go through all the CMake
> documentation items and add a line about when which feature was added.
>
> Everyone looks into his local CMake documentation and uses what he finds
> in there. And then it breaks on older versions. You currently have no
> chance to know what works but to install all older versions and do a
> binary search in the documentation. That simply does not scale.
>
> Eike
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Adding that information in the documentation would be good, I agree.
(Although quite time consuming and costly for somebody...)

But the best practice should be this:

If you are using CMake 2.8.3 exclusively to develop features in your
source tree's CMakeLists files (or included .cmake scripts) then you
need to say "cmake_minimum_required(VERSION 2.8.3)" just to be on the
safe side.

If you want to support CMake 2.6.4 (or whatever previous version you
require, for whatever reason), then you should be using *that* version
for your local development, and have that be the
cmake_minimum_required version. And use that version to look up
documentation...


David