Re: VC++2003: Methods implemented outside class body are never inlined for templates that are instantiated with __declspec(dllimport)

Tech-Archive recommends: Fix windows errors by optimizing your registry

From: Felix I. Wyss (felixw_at_inin.com)
Date: 03/16/05 

Date: Tue, 15 Mar 2005 21:53:42 -0500

> Actually, I don't believe that they are. If the function wasn't
> originally introduced with the inline keyword the compiler is free to
> ignore any subsequent request to inline it.

I'm sorry, but you're wrong. From the standard:

9.3-2
  "A member function may be defined (8.4) in its class definition,
  in which case it is an inline member function (7.1.2), [...]"

I think you're confusing it with this one:

9.3-3
  "An inline member function [...] may also be defined outside of its
  class definition provided either its declaration in the class
  definition or its definition outside of the class definition declares
  the function as inline."

> Change this to
>
> inline T foo() const;

Doesn't matter, see above. At any rate, this has no bearing on the issue
at hand anyway. After all, VC *does* inline the member functions if they
are implemented in the template class body (without the "inline" qualifier).
It doesn't inline them if they are defined outside the template class body
with the "inline" qualifier.

>> The fact that the VC compiler treats them differently in some cases
>> must be considered a bug.
>
> I don't think so. Whether a function is inlined or not is not observable
> behavior according to the C++ standard, so the compiler's free to inline
> or not at its sole discretion - including never inliing or always inlining
> or inlining only functions that contain an odd number of source tokens (or
> functions
>
> I'll admit it's quirky, and perhaps unexpected, but I don't think it can
> be classified as a compiler bug.

Well, that may be technically true, but I consider arbitrarily generating
poor
code for, according to the standard, semantically equivalent language
constructs a bug -- or at least a very dubious "feature" that should be
fixed.

--Felix

Relevant Pages

  • Re: Using inline
    ... > of a member function went if it was to be inline. ... header file in all source files that use the class. ... In order for the compiler to generate code for a function inline, ...
    (alt.comp.lang.learn.c-cpp)
  • Re: What is the gain of "inline"
    ... the absence of an explicit "inline" and thats when the definition of a ... member function is included in the class definition. ... A function in C++ is never mandated to be inline. ...
    (comp.lang.c)
  • Re: What is the gain of "inline"
    ... member function is included in the class definition. ... A function in C++ is never mandated to be inline. ... mandates an actual inline. ...
    (comp.lang.c)
  • Re: Templates and Non-Inline Functions
    ... within the class definition, so it's not going to be inlined. ... If the function really is just a "return somethingelse", the compiler ... might inline it however you define it. ... The safest way to avoid inlining is to make the function too big. ...
    (microsoft.public.vc.mfc)
  • Re: confusion with copy constructor and operator overloading
    ... So do I if the class definition is short. ... before other member functions that use them. ... > to determine weather to make them inline or not. ... inline function slow down compilation ...
    (comp.lang.cpp)