Hi,
Alberto Luaces wrote:
> Hi Paul,
>
> El Miércoles 21 Enero 2009ES 17:59:03 Paul Melis escribió:
>
>> Hi Alberto,
>>
>>> I'd prefer not to tag the header files because then you'd have to modify
>>> your source code when using different versions (osg-2.6, osg-2.7,
>>> osgDB-2.6, osgDB-2.7, and so on...) I think it's preferable to install
>>> *development* libraries on different locations. Then you can easily
>>> select which one do you want to use modifying less paramenters.
>>>
>> What you describe is not exactly what I mean. For example, VTK (made by
>> Kitware, who also made CMake) uses the following layout
>> ....
>> By specifying -I<osg-root>/include/osg-2.8 -L<osg-root>/lib/osg-2.8 to,
>> for example, gcc will make it find the correct headers, while you can
>> still write
>> #include <osg/Alpha>
>> ....
>>
>> in your code. Compiling your sources against a different OSG version
>> would then use -I<osg-root>/include/osg-2.10 -L<osg-root>/lib/osg-2.10
>>
>>
>
> Now I see that you were referring to bury the headers one level deeper.
> However as you said it would force you to specify the include path even in
> the simplest programs (no more "gcc test.cpp"). This is just a personal
> opinion, though :)
>
More or less. In the current situation you are forced to organize things
yourself if you want to have more than one OSG version available.
I was just wondering if CPack had a solution for this, as that is also
made by Kitware.
>
>>> For example, my system has version 2.4.0, but I usually compile also the
>>> SVN version in my home directory. When I want to link against the SVN
>>> version, I point PKG_CONFIG_PATH to my SVN installation directory, so the
>>> compilation goes against the new version without altering the code
>>> neither the build system.
>>>
>> And thereby you completely ignore a useful feature of pkg-config: it can
>> give you paths for different installed versions. If you would have, for
>> example, OSG 2.6.1 installed in ~/osg-2.6 and occassionaly compile the
>> SVN version and install it to ~/osg-svn then each could have an
>> openscenegraph.pc file in their lib/pkgconfig directory, but with
>> differing contents. By specifying both ~/osg-2.6/lib/pkgconfig and
>> ~/osg-svn/lib/pkgconfig in PKG_CONFIG_PATH you can use "g++ -c ...
>> `pkg-config --exact-version=2.6` --cflags --libs`", or specify a
>> different version when you want. The version value passed would then
>> have to be controlled by the build system (easy with, for example,
>> scons). But I can see that without build system support for easily
>> changing what OSG version you want to compile against this would be
>> annoying.
>>
>
> I don't follow you here. If I set PKG_CONFIG_PATH where I installed the svn
> compilation, I still have the system .pc file as a fallback, so I can choose
> which one I want.
Right, I can see what you do, but it involves changing your environment
settings to select what to compile against.
> What do you mean by "without build system"? Pure Makefiles?
> Then you can set the version as a variable and have whichever you want
> without modifying anything on your program... ("make VERSION=2.6.3",
> even "make CXXFLAGS=`pkg-config --exact-version=2.6 --cflags`")
>
I typed "without build system *support*", meaning if you have a build
system that doesn't allow you to easily select against which libraries
you want to compile.
E.g., with scons you basically control the whole build environment,
including -I and -L flags so it's quite easy to make a build script that
allows you link against OSG 2.6 with "scons ver=2.6" and against OSG svn
with "scons ver=svn".
>>> Howewer once the software is built, of course all versions can coexist on
>>> the same directory, at least on Linux :)
>>>
>> No they can't, as the include dirs of different minor versions (e.g. 2.6
>> versus 2.8) are not guarded by a version number. Libraries and plugins
>> are safe, though.
>>
>
> When I said *built* software I meant libraries :) Sorry, I'm always thinking
> of avoiding to put several version sets of include files on system
> directories :)
>
Ah, yes, the run-time is versioned, but the "SDK" isn't.
Paul
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