This is about c-compiler gcc. Discussion have started on other threads off-topic, it might be better to have one dedicated.

Release dates:
GCC 4.2.1 release (2007-06-18)
GCC 4.2.4 release (2008-05-19)
GCC 4.4.6 release (2011-04-16)
GCC 4.6.2 release (2011-08-26)

Maemo5 has gcc-4.2.1. We have already encountered programs, which need newer compiler. And there are some bug fixed on ARM-version of gcc-4.4 (atomic types are in 4.2 but actually not working on ARM until 4.4). Third reason is 4.6 has and will have more optimization on ARM (by e.g. Linaro, http://www.linaro.org)

Some developers are already using Tom Tanner's gcc-4.4 (
http://n900.tannerlab.com/pool/free/g/gcc-4.4/ ), but it is not in extras (-devel).

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I have started to push new compiler to the extras-devel. There are needed libraries and newer tools (e.g. bison-2.4 and make-3.81) on repository (and autobuilder can use them). Seems to me that 4.2 can compile 4.6, so we can skip 4.4.

Some random thoughts:
*On i386-target multilib should not be used.
*Virtualized/emulated environments lacks RAM/SWAP, so -j1 might be the only way (I think issue is generated insn-attrtab.c)
*It might be must to use --disable-bootstrap (bootstrap="compiler test can it compile itself during process" (seems to be memory issue))
*I had some problems to not compile java

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When program is compiled with newer gcc, it needs also newer libstdc++ (Is this true with only c++ applications?) .Do old programs work with new libstdc++ or should there be both then installed on device? (until we can recompile every program)
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Should this be packages gcc-4.6 (building) and libstdc++6-4.6 (runtime)? Or could this overwrite gcc and libstdc++6?
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This is Work In Progress, join discussion if you have something to contribute.

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Edit:
Reason's for newer compiler:
*There are more and more applications which can't be built with old compiler, due bugs in old compiler or new features on new compiler. This is proven to be true. (But we can still claim that those new applications are not needed, or we can port them to use old compiler)
*Possible better optimization: E.g. Linaro is making gcc 'better' for ARM speaking code size and execution speed. It is not (yet) proved that this happens on N900.
*THUMB2
http://www.cnx-software.com/2011/04/...e-performance/
(I have not seen tests for N900)
*NEON (whatever this means...)