Installing a 64 bit OS or keeping a 32 bit OS?

[Jef Driesen]

Chris Jones wrote:
>> Can I still run 32bit applications? 
> 
> Yes, absolutely. You will need to install some 32 bit system libraries 
> along side their 64 bit versions (this may be default, I don't have a 64 
> bit ubuntu so cannot be sure here. Someone else who does can clarify this).

But if I install a 32bit application, I also need to install a 32bit 
version of all its dependencies? Or is that not necessary?

>> The laptop is mainly used for software development, so I would like to
>> have a 64bit environment for testing my code. But I still need to be
>> able to compile for a 32bit environment (and preferable test them as
>> well). Is that possible?
> 
> yes, with gcc just use the "-m32" flag and that will force the 64 bit 
> compiler to build 32 bit binaries.

Does that also work when linking with other libraries? I suppose a 64bit 
Ubuntu will have only 64bit libraries installed. How do I build the 
32bit binary in that case?