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From: ssimmons@convex.com (Steve Simmons)
Newsgroups: comp.lang.c++
Subject: >>> Virtual functions and inline ...
Message-ID: <ssimmons.667836666@convex.convex.com>
Date: 1 Mar 91 14:11:06 GMT
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>From: gas@cs.nott.ac.uk (Alan Shepherd)
> Organization: Nottingham University
> Date: 28 Feb 91 14:15:48 GMT
> Subject: Virtual functions and inline

> Is it okay to declare virtual functions inline ?  Even though the code
> to be excuted is substituted rather than a function call made, does
> the correct method still get called ?


	This is not a wise thing to do although the language will
	allow it.   

	In the first place, you are never guaranteed that a routine 
	is inlined. It is only a suggestion to the compiler.  If
	the routine is either too complicated or a virtual function,
	then a static copy of the routine will be placed in the 
	compiled module.   Thus, a routine that was coded as inline 
	may cause a performance degradation because it may consume
	much more space when it is not physically inlined.
	With a virtual function, a copy of that routine will be 
	created for every module that has at least one instantiation 
	of that class. 

	The language allows it but you would not be deriving any 
	better performance.  I have become very negative 
	towards the inline feature of a language like Ada's inline
	pragma or C++'s inline definition.  After all, inlining is 
	not part of the algorithm, just a performance enhancement. 
	Inlining should be done as part of the optimizing phase.

	Thank you. 


						Steve Simmons