Re: C++ virtual function calls

martelli@cadlab.it (Alex Martelli)
Sun, 5 Nov 1995 19:44:33 GMT

          From comp.compilers

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Re: C++ virtual function calls joe@sanskrit.ho.att.com (1995-10-30)
Re: C++ virtual function calls jplevyak@violet-femmes.cs.uiuc.edu (John B. Plevyak) (1995-11-09)
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| List of all articles for this month |

Newsgroups: comp.compilers
From: martelli@cadlab.it (Alex Martelli)
Keywords: C++, optimize, comment
Organization: Cad.Lab Spa, Bologna, Italia
References: 95-10-029 95-11-020
Date: Sun, 5 Nov 1995 19:44:33 GMT

joe@sanskrit.ho.att.com (Joe Orost) writes:


>I don't think it is legal to hoist the virtual function lookup
>out of the loop:


>for( ...) {
> p->virt_func();
>}


>because "p" is passed to virt_func as "this", and therefore the
>function could change the subtype of "p", causing a different
>function to be called next time around the loop!


Hmmmm... you mean by doing something like "~typeofp(); new(p) typeofp(22);"?
I'm not sure this would be legal -- an interesting question for
comp.std.c++, if the comp.compiler moderator would pretty please
crosspost this to there (crossposting on two mod groups at once
can really be -- ahem -- "interesting"!-).




Alex
--
DISCLAIMER: these are TOTALLY personal opinions and viewpoints, NOT connected
in any way with my employer, nor any other organization or individual!
Email: martelli@cadlab.it Phone: +39 (51) 597313
CAD.LAB s.p.a., v. Ronzani 7/29, Casalecchio, Italia Fax: +39 (51) 597120
[No need to crosspost, it's not allowed. -John]
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