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List:       kde-devel
Subject:    questions about c++ templates
From:       Benoît_Jacob <jacob () math ! jussieu ! fr>
Date:       2006-08-18 16:11:12
Message-ID: 200608181811.12267.jacob () math ! jussieu ! fr
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Hi!

I've got a few questions, so if you can help me that'll result in a better 
kdesupport/eigen library ;)

1. when you instantiate a template class, does the compiler generate code only 
for those methods that are getting called for this particular template 
instantiation, or does it generate code for all methods?

Concretely:

-------------------------------------------------------------------
template<class T> class M
{
	// 500 methods that DON'T call one another
	void method1();
	...
	void method500();
};

...

M<int> m;
m.method1();
-------------------------------------------------------------------

does that generate code for the 499 unused methods of M<int> ?

2. when you instantiate the same template class for various pointer types, 
does the compiler generate code only once ?

Concretely:
M<int *> mi;
M<SomeClass *> mc; // does that generate code for M<SomeClass *> or does
	// that share code with M<int *> ?

3. In my code, I have a class A (it's an assignable data type) and it would be 
natural for me at some point to do

QList<A> l;

and then to use only a few elementary methods of QList<A> (like append 
elements and do a foreach). How much binary size would be replaced by doing

QList<A *> l;

That would be less convenient for me, so I'd like to know if it's worth it.

Benoit
 
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