I saw that for previous versions of maemo there is a C/C++ application. Can we have it for maemo 5? I am a student and it's very cool to write and run my exercises on n900

Do you mean C/C++ compiler on Maemo?

yeah write compile and run. I ve seen this but i dont think it wiil work on n900

Isn't gcc/automake/etc already available in the SDK repository?...

Yes, these are in the SDK repository (see for example http://maemo.org/packages/view/gcc-4.2). Can the SDK repository be used on a real device, and if so, is it safe, or is it risky like enabling extras-devel?

any reply on this???

I've had the sdk repository enabled on my n800 for quite a while - I've had no problems. YMMV

You can enable extras-devel or the SDK repo but you must not apt-get upgrade with these repos enabled. Just for installing gcc it should be safe.

Anyway, do this only if you know how to reflash a broken device.

yes, but on a default n900 its won't work without some cleaning (for the reason see optification)
follow pycages advice, do not do this if you don't know how to cure any problems.

that out of the way,

i generally add the repo
deb http://repository.maemo.org fremantle/sdk free non-free

then
apt-get update
apt-get install build-essential

then remove the repo again and apt-get update once again.

as I say, it will fail because its large, but its the full set of things required for on device compilation



note, this doesnt bring in autotools or dpkg
so no ./configure stage works, and no dpkg-buildpackage will run.
(normal make files and find an alternative for packaging)

if you don't need them and can work with makefiles its certainly usable and fast.
if you need -dev headers for libraries, expect even more space, I find nowadays I can get by mostly with libliqbase-dev

hth

Also, the most important thing for a big build (at least on the n8x0's using Easy Debian) is to set your tmp dir to storage, not memory. For example:

mkdir /bigpartition/tmp
export TMPDIR=/bigpartition/tmp
fakeroot dpkg-buildpackage ...