From -1711397944791097535 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,a69618ea97f65037 X-Google-Attributes: gidf78e5,public From: "Paul D. DeRocco" Subject: Re: nested functions Date: 1998/04/28 Message-ID: <354563EA.C5F51A1F@ix.netcom.com>#1/1 X-Deja-AN: 348335284 Approved: Fergus Henderson Content-Transfer-Encoding: 7bit References: <6hac23$8lb$1@news2.isdnet.net> <353F904F.2EFDC21D@ix.netcom.com> <6hpf3p$9ci$1@toralf.uib.no> X-Original-Date: Tue, 28 Apr 1998 01:06:50 -0400 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Organization: Vast Right-Wing Conspiracy X-NETCOM-Date: Tue Apr 28 12:08:27 AM CDT 1998 X-Auth: PGPMoose V1.1 PGP comp.std.c++ iQBFAgUANUV17uEDnX0m9pzZAQHhrAF+MNkkz1VQBFZ1hcjOw4mhKNgOcjY6FPQ6 vJiUXmAKgFt7eYaLqGX5eU/z3gOgi/np =Zxhl Newsgroups: comp.std.c++ Igor Boukanov wrote: > > GCC uses on fly code generation to make possible free mixture of > pointers > to non-nested and nested functions that result in no overhead for > ordinary > pointers. Basically it constructs a code that that would restore > necessary > context and then call the nested function itself. In other words, GCC generates a thunk at runtime that passes the context into the function, perhaps by loading it into a register? This is what Win16 used to do for callbacks, although it was loading the DS register with the instance's data segment. The problem is, where do you put these thunks? The obvious place is on the stack, like any other temporary, but many architectures don't let you execute code out of pages that are used for data. This means the compiler has to allocate the thunk somewhere else, and include the necessary exception handling code to guarantee that the thunk is deallocated when the stack is unwound. Certainly doable, but slightly messy. It's probably worth it, though. -- Ciao, Paul --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://reality.sgi.com/austern_mti/std-c++/faq.html ]